Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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17 pages, 9132 KiB  
Article
Aluminum Removal from Rare Earth Chloride Solution through Regulated Hydrolysis via Electrochemical Method
by Yaoyao Zhu, Jian Li, Dongyue Xie, Hui Zhang, Man Li, Binfeng Xu, Xuxia Zhang, Yangyang Xie and Tao Qi
Separations 2024, 11(5), 149; https://doi.org/10.3390/separations11050149 - 12 May 2024
Viewed by 969
Abstract
Due to the coexistence of Al3+ and RE3+ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By [...] Read more.
Due to the coexistence of Al3+ and RE3+ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By controlling the current density and electrolytic time, the rate of hydroxyl ion production was regulated, and the selective separation of rare earth and aluminum was realized according to the different precipitation sequences. By altering the temperature, current density, pH value, and other parameters, the separation performance of aluminum from rare earth in mixed rare earth chloride systems was systematically investigated. The removal rate of aluminum reached 88.35%, and the loss rate of rare earth was only 5.99% under optimized conditions. Compared with traditional neutralization hydrolysis, the new process showed higher efficiency and lower rare earth loss rate. Furthermore, a kinetic analysis of aluminum precipitation revealed that the reaction adhered to pseudo-first order kinetics. Additionally, the precipitate obtained via separation and filtration was amorphous alumina hydroxide with a small amount of rare earth attached. No reagent was consumed for the new process, which was more efficient and cleaner, providing a new idea for removing aluminum impurities from rare earth solutions. Full article
(This article belongs to the Section Purification Technology)
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24 pages, 10774 KiB  
Review
Achievements in Preparation of Cyclodextrin–Based Porous Materials for Removal of Pollutants
by Kaiyue Bao, Anyun Zhang, Yiyao Cao and Lei Xu
Separations 2024, 11(5), 143; https://doi.org/10.3390/separations11050143 - 7 May 2024
Viewed by 623
Abstract
Cyclodextrin–based porous materials have been widely applied in removing various organic pollutants from water environments, due to their unique physical and chemical properties, like the size–matching effect and hydrophobic interaction. Large numbers of hydroxyl groups in its external structure give cyclodextrin a high [...] Read more.
Cyclodextrin–based porous materials have been widely applied in removing various organic pollutants from water environments, due to their unique physical and chemical properties, like the size–matching effect and hydrophobic interaction. Large numbers of hydroxyl groups in its external structure give cyclodextrin a high solubility in water, but the existence of these hydroxyl groups also endows cyclodextrin with the ability to be chemically modified with various functional groups to reduce its solubility in water and, meanwhile, to develop some novel functionalized cyclodextrin–based porous materials for selective removal of the target organic pollutants. This review focuses on the recent development in the synthesis of cyclodextrin–based porous materials (crosslinked cyclodextrin polymers and immobilized cyclodextrins), as well as highlighting their applications and mechanisms in the removal of dyes, endocrine disruptors, and mixed pollutants from water. Finally, the challenges and future perspectives in related research fields are discussed. Full article
(This article belongs to the Special Issue Adsorption and Remediation of Emerging Pollutants from Water and Soil)
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18 pages, 8322 KiB  
Article
Decoding the Volatile Profile of White Romanian Fetească Wines
by Fulvia-Ancuța Manolache, Denisa-Eglantina Duță, Gabriela Daniela Criveanu-Stamatie, Teodora-Alexandra Iordache and Maria-Cristina Todașcă
Separations 2024, 11(5), 141; https://doi.org/10.3390/separations11050141 - 3 May 2024
Viewed by 665
Abstract
The wine’s volatilome, most of the time, defines not only its aroma, but also, its major attributes. In the case of wines, the authentication process has become imperative, in light of increased production of alcoholic beverages; consequently, reliable analytical methods have served for [...] Read more.
The wine’s volatilome, most of the time, defines not only its aroma, but also, its major attributes. In the case of wines, the authentication process has become imperative, in light of increased production of alcoholic beverages; consequently, reliable analytical methods have served for it. Therefore, the goal of this research was to establish the global volatile profile of traditional Romanian white wines from Fetească varieties (Fetească albă, Fetească regală) in order to identify its unique characteristics by means of a headspace solid-phase microextraction coupled with gas chromatography analysis (HS-SPME/GC-MS) and e-Nose devoted techniques. Statistics was also employed aimed at differentiating the analyzed wine by varietal groups. Consequently, 23 volatile compounds were detected and quantified in 39 Fetească white wine samples originating from various production areas (Muntenia, Oltenia, Transylvania, Banat and Dobrogea), then further classified according to their odor thresholds in five aromatic classes (floral, fruity, sweet, lactic (cheesy) and other). In addition, statistics (Principal Component Analysis (PCA), Hieratical Clustering Analysis (HCA)) were used aiming to differentiate the analyzed varietal groups. The outcomes have pointed out the existence of distinct clusters connected with ethyl esters or alcohol composition and production year, depending on each examined variety. Full article
(This article belongs to the Topic Advances in Analysis of Food and Beverages)
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12 pages, 1710 KiB  
Article
Pomegranate Juice Clarification Using Ultrafiltration: Influence of the Type of Variety and Degree of Ripeness
by Asunción M. Hidalgo, José A. Macario, Marta Abellán-Baeza, Teresa Sánchez-Moya, Rubén López-Nicolás and Fulgencio Marín-Iniesta
Separations 2024, 11(5), 134; https://doi.org/10.3390/separations11050134 - 26 Apr 2024
Viewed by 826
Abstract
Fruit consumption guarantees the supply of most of the necessary nutrients for a complete and balanced diet, as it is a relevant source of vitamins, minerals, and antioxidants. In particular, pomegranate has very interesting medicinal properties, such as an anti-inflammatory effect and the [...] Read more.
Fruit consumption guarantees the supply of most of the necessary nutrients for a complete and balanced diet, as it is a relevant source of vitamins, minerals, and antioxidants. In particular, pomegranate has very interesting medicinal properties, such as an anti-inflammatory effect and the protection of the cardiovascular system, among others. During pomegranate juice production, it appears cloudy and must be clarified to remove suspended solids such as colloids and high-molecular weight tannins. The membrane clarification process is a cost-effective alternative to the conventional methods, resulting in a high-quality product. In this work, the clarification of pomegranate juice using the Triple System Model F1 membrane module was carried out for the Mollar and Wonderful varieties with early and late maturity. Three ultrafiltration membranes with different molecular weight cut-off and different chemical compositions were used. The rejection coefficient and permeate flux (which represent the selectivity of the membranes and the process efficiency, respectively) were measured. GR-40PP showed the best results in terms of membrane selectivity and process efficiency, achieving adequate physicochemical juice parameters. Regarding the comparison of the maturity degree, in general terms, the Mollar variety showed better results. Ripe pomegranates showed greater selectivity, while the process efficiency was higher for the early samples. Full article
(This article belongs to the Section Analysis of Natural Products and Pharmaceuticals)
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24 pages, 5748 KiB  
Review
Laser Manufacturing of Superwetting Oil–Water Separation Materials: A Review
by Wei Xiong, Linfeng Zhu, Ruisong Jiang and Chaolang Chen
Separations 2024, 11(4), 126; https://doi.org/10.3390/separations11040126 - 19 Apr 2024
Viewed by 848
Abstract
The frequent occurrence of oil spills and the massive discharge of oily wastewater pose a significant threat to sustainable and healthy human development. Therefore, it is of importance to effectively separate oil–water mixtures. Inspired by nature, many superwetting surfaces/materials for oil–water separation have [...] Read more.
The frequent occurrence of oil spills and the massive discharge of oily wastewater pose a significant threat to sustainable and healthy human development. Therefore, it is of importance to effectively separate oil–water mixtures. Inspired by nature, many superwetting surfaces/materials for oil–water separation have been developed in recent years. However, these surfaces/materials are subject to certain limitations and are unable to fully meet practical needs. With the advancement of laser technology, a novel solution has been provided for fabricating superwetting oil–water separation materials. Based on the design theory and separation mechanism, this paper summarizes the research progress of the laser-fabricated superwetting surfaces/materials for oil–water separation in recent years. First, the basic wetting theory, design strategy, and oil–water separation mechanism of the laser-fabricated materials are introduced in detail. Subsequently, the laser-fabricated oil–water separation materials, including superoleophilic/superhydrophobic materials, superhydrophilic/superoleophobic materials, and materials with reversible or superamphiphilic wettability, are systematically summarized and analyzed. Finally, the challenges and future research directions of laser-fabricated superwetting oil–water separation materials are discussed. Full article
(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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19 pages, 4852 KiB  
Article
Adsorption of Fluoride from Water Using Aluminum-Coated Silica Adsorbents: Comparison of Silica Sand and Microcrystalline Silica
by Kiana Modaresahmadi, Amid P. Khodadoust and James Wescott
Separations 2024, 11(4), 125; https://doi.org/10.3390/separations11040125 - 19 Apr 2024
Viewed by 852
Abstract
Two aluminum-coated silica adsorbents were evaluated using silica sand and microcrystalline silica as aluminum-oxide-based adsorbents with different crystalline silica base materials. The aluminum coating contained mainly amorphous aluminum oxides for both aluminum-coated silica adsorbents. The adsorption of fluoride onto both adsorbents was favorable [...] Read more.
Two aluminum-coated silica adsorbents were evaluated using silica sand and microcrystalline silica as aluminum-oxide-based adsorbents with different crystalline silica base materials. The aluminum coating contained mainly amorphous aluminum oxides for both aluminum-coated silica adsorbents. The adsorption of fluoride onto both adsorbents was favorable according to the Langmuir and Freundlich adsorption equations, while the physical adsorption of fluoride occurred for both adsorbents according to the Dubinin–Raduskevish (D-R) equation. The adsorption of fluoride was stronger for aluminum-coated silica sand based on adsorption parameters from the Langmuir, Freundlich, and D-R adsorption equations, with the stronger binding of fluoride likely due to the observed greater specific adsorption. The adsorption capacity determined using the Langmuir equation was about 7 times greater for aluminum-coated microcrystalline silica primarily due to the 1.22-orders-of-magnitude-larger surface area of aluminum-coated microcrystalline silica, whereas the surface-normalized adsorption capacity was 2.4 times greater for aluminum-coated silica sand, possibly due to more aluminum being present on the surface of silica sand. Fluoride adsorption occurred over a broad pH range from 3 to 10 for both adsorbents, with nearly the same pHPZC of 9.6, while aluminum-coated microcrystalline silica displayed a higher selectivity for fluoride adsorption from different natural water sources. Full article
(This article belongs to the Section Materials in Separation Science)
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15 pages, 2394 KiB  
Article
Selective H2 Evolution and CO2 Absorption in Electrolysis of Ethanolamine Aqueous Solutions
by Satoshi Fukada, Ryosuke Sakai, Makoto Oya and Kazunari Katayama
Separations 2023, 10(11), 578; https://doi.org/10.3390/separations10110578 - 20 Nov 2023
Viewed by 1394
Abstract
Selective H2 evolution and CO2 absorption in several ethanolamine aqueous solutions are comparatively investigated using a new electrolysis reactor. H2 bubbles are generated from a cathode in any ethanolamine electrolyte, and its experimental gas evolution rates are correlated by Faraday’s [...] Read more.
Selective H2 evolution and CO2 absorption in several ethanolamine aqueous solutions are comparatively investigated using a new electrolysis reactor. H2 bubbles are generated from a cathode in any ethanolamine electrolyte, and its experimental gas evolution rates are correlated by Faraday’s first rule. No or smaller amounts of CO2 and N2 bubbles than stoichiometric ones are generated on an anode through the reaction between hydroxide ions and ethanolamine ones. No CO or O2 is observed in the system exhaust, and most of the CO2, along with N2, is still absorbed in ethanolamine aqueous solutions with the addition of KOH and/or HCOOH under high pH conditions. Variations of the concentrations of coexisting ions dissolved in the electrolytes of mono- or tri-ethanolamine (MEA or TEA) and ethylenediamine (EDA) solutions with CO2 absorption are calculated using the equilibrium constants to relate the concentrations of solute ions. Electric resistivities of the ethanolamine aqueous solutions are correlated by the pH value and are analyzed in terms of equilibrium constants among the concentrations of coexisting ions. Conditions of the MEA electrolyte to achieve high-performance electrolysis is discussed for selective H2 generation. Full article
(This article belongs to the Special Issue Advances in CO2 Adsorptive Separation for CO2 Capture)
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16 pages, 3907 KiB  
Article
Identifying the Early Post-Mortem VOC Profile from Cadavers in a Morgue Environment Using Comprehensive Two-Dimensional Gas Chromatography
by Darshil Patel, Rushali Dargan, Wesley S. Burr, Benoit Daoust and Shari Forbes
Separations 2023, 10(11), 566; https://doi.org/10.3390/separations10110566 - 10 Nov 2023
Viewed by 2170
Abstract
Understanding the VOC profile released during the early post-mortem period is essential for applications in training human remains detection dogs and urban search and rescue operations (USAR) to rapidly locate living and deceased victims. Human cadavers were sampled at the UQTR morgue within [...] Read more.
Understanding the VOC profile released during the early post-mortem period is essential for applications in training human remains detection dogs and urban search and rescue operations (USAR) to rapidly locate living and deceased victims. Human cadavers were sampled at the UQTR morgue within a 0–72 h post-mortem interval. VOC samples were collected from the headspace above the cadavers, using Tenax TA/Carbograph 5TD dual sorbent tubes, and analyzed using GC×GC-TOFMS. Multiple data processing steps, including peak table alignment and filtering, were undertaken using LECO ChromaToF and custom scripts in R programming language. This study identified 104 prevalent VOCs, some of which are linked to human decomposition, while others are connected to the persistence of living scent. Principal Component Analysis (PCA) further highlighted that VOC profiles can change dynamically over time, even in a controlled setting. The findings underscore the complexity and variability in VOC profiles during the early post-mortem period. This variability is influenced by multiple factors including the individual’s biological and physiological conditions. Despite the challenges in characterizing these profiles, the identified VOCs could potentially serve as markers in forensic applications. The study also highlights the need for additional research to build a dataset of VOCs for more robust forensic applications. Full article
(This article belongs to the Special Issue Chemical Separations in Criminalistics)
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25 pages, 4971 KiB  
Article
Evaluation of CO2 Adsorption Parameters in Fluidised Zeolite 13X Beds Using Non-Linear Multivariate Optimisation
by Alessio Caravella, Giuseppe Prenesti, Salvatore De Luca, Maria Turano, Flaviano Testa and Rossella Girimonte
Separations 2023, 10(11), 558; https://doi.org/10.3390/separations10110558 - 3 Nov 2023
Viewed by 1970
Abstract
This work is part of a research project aimed at studying potential sorbents for CO2 capture. The main parameters characterising the adsorption process of zeolite 13X were derived with the aim of overcoming the limits of experimental analysis and thus predicting the [...] Read more.
This work is part of a research project aimed at studying potential sorbents for CO2 capture. The main parameters characterising the adsorption process of zeolite 13X were derived with the aim of overcoming the limits of experimental analysis and thus predicting the performances of the materials of interest. In particular, the main parameters that control the adsorption process of CO2 in zeolite 13X were evaluated through parametric optimisation. This systematic procedure allows for the prediction of the performances of the materials at different operating conditions, identifying the most suitable ones for the case under consideration. Another important application lies in the possibility of a preliminary study of a potential process scale-up for future industrial use. The captured carbon dioxide can be stored or used as a reagent in the production of products with higher economic values, such as methanol, DME and others. Full article
(This article belongs to the Special Issue Advances in CO2 Adsorptive Separation for CO2 Capture)
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21 pages, 3743 KiB  
Article
A Rule-Based Automated Chemical Recognition Algorithm for a Multi-Cell Multi-Detector Micro Gas Chromatograph
by Qu Xu, Yutao Qin and Yogesh B. Gianchandani
Separations 2023, 10(11), 555; https://doi.org/10.3390/separations10110555 - 31 Oct 2023
Cited by 1 | Viewed by 1501
Abstract
A chemical recognition algorithm is an integral part of any autonomous microscale gas chromatography (µGC) system for automated chemical analysis. For a multi-detector µGC system, the chemical analysis must account for the retention time of each chemical analyte as well as the relative [...] Read more.
A chemical recognition algorithm is an integral part of any autonomous microscale gas chromatography (µGC) system for automated chemical analysis. For a multi-detector µGC system, the chemical analysis must account for the retention time of each chemical analyte as well as the relative response of each detector to each analyte, i.e., the detector response pattern (DRP). In contrast to the common approaches of heuristically using principal component analysis and machine learning, this paper reports a rule-based automated chemical recognition algorithm for a multi-cell, multi-detector µGC system, in which the DRP is related to theoretical principles; consequently, this algorithm only requires a small amount of calibration data but not extensive training data. For processing both the retention time and the raw DRP, the algorithm applies rules based on expert knowledge to compare the detected peaks; these rules are located in a customized software library. Additionally, the algorithm provides special handling for chromatogram peaks with a small signal-to-noise ratio. It also provides separate special handling for asymmetrical peaks that may result from surface adsorptive analytes. This work also describes an experimental evaluation in which the algorithm used the relative response of two complementary types of capacitive detectors as well as a photoionization detector that were incorporated into the µGC system of interest. In these tests, which were performed on chromatograms with 21–31 peaks for each detector, the true positive rate was 96.3%, the true negative rate was 94.1%, the false positive rate was 5.9%, and the false negative rate was 3.7%. The results demonstrated that the algorithm can support µGC systems for automated chemical screening and early warning applications. Full article
(This article belongs to the Special Issue Development of Materials for Chromatographic Separation)
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15 pages, 2776 KiB  
Article
Application of Choline Chloride-Based Deep Eutectic Solvents in the Synthesis of Hydrazones
by Valentina Bušić, Sunčica Roca and Dajana Gašo-Sokač
Separations 2023, 10(11), 551; https://doi.org/10.3390/separations10110551 - 29 Oct 2023
Viewed by 2084
Abstract
The synthesis of 14 hydrazone compounds derived from pyridoxal, pyridine-4-carbaldehyde, and quinoline-2-carbaldehyde using two methods, conventional method in deep eutectic solvents (DESs) and effective combination of ultrasound and DESs, is presented in this paper. In addition, the possibility of using 12 choline chloride [...] Read more.
The synthesis of 14 hydrazone compounds derived from pyridoxal, pyridine-4-carbaldehyde, and quinoline-2-carbaldehyde using two methods, conventional method in deep eutectic solvents (DESs) and effective combination of ultrasound and DESs, is presented in this paper. In addition, the possibility of using 12 choline chloride (ChCl)-based DESs as an alternative to organic solvents was investigated. The results show that the application of ultrasound not only improves the reaction yield but also shortens the reaction time. The prepared compounds synthesized at room temperature were analyzed via NMR spectroscopy and MS spectrometry. The studies confirmed that the DESs ChCl:malonic, oxalic, levulinic, and trans-cinnamic acid can be excellent alternatives to classical organic solvents. By the combined use of DESs and the ultrasonic method, compound 11 was obtained in a nearly quantitative yield of 98% in DES ChCl:oxalic acid. The advantages of using DESs as reaction media are that they are biodegradable, nontoxic, recyclable, and can be easily prepared with inexpensive starting materials. The results of recycling DESs show that they can be used up to the fourth recycling cycle without significantly changing the reaction yield. Full article
(This article belongs to the Special Issue Application of Deep Eutectic Solvents in Green Separation Chemistry)
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22 pages, 856 KiB  
Article
Aroma Profile of Grapevine Chips after Roasting: A Comparative Study of Sorbara and Spergola Cultivars for More Sustainable Oenological Production
by Veronica D’Eusanio, Lorenzo Morelli, Andrea Marchetti and Lorenzo Tassi
Separations 2023, 10(10), 532; https://doi.org/10.3390/separations10100532 - 6 Oct 2023
Cited by 3 | Viewed by 1504
Abstract
This study aimed to compare the aroma profiles of Sorbara and Spergola grapevine prunings roasted at different temperatures (120, 140, 160, 180, 200, and 240 °C). One potential application of grapevine prunings is their use as infusion chips to enhance and improve the [...] Read more.
This study aimed to compare the aroma profiles of Sorbara and Spergola grapevine prunings roasted at different temperatures (120, 140, 160, 180, 200, and 240 °C). One potential application of grapevine prunings is their use as infusion chips to enhance and improve the aging processes of alcoholic beverages and vinegars. Aromatic compounds impart unique flavors and contribute to the complexity of the final products. Thermogravimetry–mass spectrometry coupled with evolved gas analysis (TGA-MS-EGA) was conducted to identify the thermal steps at which substantial changes occurred in the wood matrix. Solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS) was used for the analysis of volatile compounds. Several key volatile compounds were identified, showing variations in their concentrations as a function of cultivar and roasting temperature. Furan derivatives, such as furfural, and phenolic compounds, such as guaiacol and vanillin, were the two main chemical classes of volatile compounds that predominantly defined the aroma of grapevine chips roasted above 180 °C. At lower roasting temperatures, some aldehydes, such as hexanal and terpenes, defined the aroma profiles of the samples. By repurposing waste materials, this application offers a pathway for environmentally conscious viticulture and sustainable practices within the food industry. Full article
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34 pages, 1646 KiB  
Review
Innovative Solutions for Food Analysis: Microextraction Techniques in Lipid Peroxidation Product Detection
by Jorge A. Custodio-Mendoza, Ana M. Ares-Fuentes and Antonia M. Carro
Separations 2023, 10(10), 531; https://doi.org/10.3390/separations10100531 - 4 Oct 2023
Cited by 5 | Viewed by 1928
Abstract
Lipid peroxidation, the most aggressive reaction in food, results in the formation of reactive organic compounds that detrimentally impact food sensory qualities and consumers’ health. While controlled lipid peroxidation can enhance flavors and appearance in certain foods, secondary peroxidation products lead to sensory [...] Read more.
Lipid peroxidation, the most aggressive reaction in food, results in the formation of reactive organic compounds that detrimentally impact food sensory qualities and consumers’ health. While controlled lipid peroxidation can enhance flavors and appearance in certain foods, secondary peroxidation products lead to sensory deterioration in a variety of products, such as oils, alcoholic beverages, and meat. This publication reviews the use of modern analytical techniques for detecting and quantifying carbonyl compounds, i.e., secondary lipid peroxidation products. The paper focuses specifically on microextraction-based methods: dispersive liquid-liquid microextraction (DLLME), solid-phase microextraction (SPME), and gas-diffusion microextraction (GDME). These techniques offer efficient and sensitive approaches to extracting and quantifying lipid oxidation products and contribute to the understanding of oxidative deterioration in various food products. The review outlines recent advancements, challenges, and limitations in these microextraction techniques, as well as emphasizes the potential for further innovation and improvement in the field of food analysis. Full article
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21 pages, 2144 KiB  
Article
Adsorption of Lactose Using Anion Exchange Resin by Adding Boric Acid from Milk Whey
by Hideo Maruyama and Hideshi Seki
Separations 2023, 10(10), 530; https://doi.org/10.3390/separations10100530 - 3 Oct 2023
Viewed by 1717
Abstract
The influence of adding boric acid (BA) on the adsorption behavior of lactose onto an anion exchange resin (IRA402) was investigated. By adding BA, the amount of lactose adsorbed onto IRA402 was increased ca. 20% compared to without adding BA. In the presence [...] Read more.
The influence of adding boric acid (BA) on the adsorption behavior of lactose onto an anion exchange resin (IRA402) was investigated. By adding BA, the amount of lactose adsorbed onto IRA402 was increased ca. 20% compared to without adding BA. In the presence of BA, ca. 70% of the adsorbed lactose could desorb from IRA402, while the absorbed lactose hardly desorbed in the absence of BA. Lactose molecules were considered to bind to tertiary amine group on IRA402 by Maillard reaction. The optimum conditions of the dosage of BA and pH were found at the molar ratio of BA to lactose ranging from 1–2, and pH 7–9. The kinetics and equilibrium of lactose adsorption could be explained by the Langmuir adsorption model (best model). In the case of a real whey solution, phosphate strongly affected the adsorption behavior and could be removed as precipitation from the whey over pH 10. Whey proteins had little effect on lactose adsorption, which was ca. 30% less than that in the model system. Moreover, the different kinds of whey proteins and amino acids had little effect on the amount adsorbed. Minerals in the whey may also be considered to be responsible for the decreased adsorption in the whey. Full article
(This article belongs to the Section Separation Engineering)
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16 pages, 4470 KiB  
Article
CoFe2O4/MoS2@Au: Multifunction Z-Scheme Heterojunction for SERS Monitoring and Photocatalytic Degradation of Fungicides
by Qirong Dong, Qingyi Wei and Hongbin Pu
Separations 2023, 10(10), 526; https://doi.org/10.3390/separations10100526 - 28 Sep 2023
Viewed by 1247
Abstract
Efficient detection and degradation of fungicides are greatly concerned with aquatic food safety. Herein, a multifunction CoFe2O4/MoS2@Au (ACMS) composite was synthesized for crystal violet (CV) and malachite green (MG) photocatalytic degradation and SERS determination. As the construction [...] Read more.
Efficient detection and degradation of fungicides are greatly concerned with aquatic food safety. Herein, a multifunction CoFe2O4/MoS2@Au (ACMS) composite was synthesized for crystal violet (CV) and malachite green (MG) photocatalytic degradation and SERS determination. As the construction of the Z-scheme heterostructure of ACMS, which enhanced the light absorption capability and the separation efficiency of photoexcited carrier significantly, ACMS possessed an excellent photocatalytic performance with a degradation rate of 94.76% for CV under simulated solar light irradiation. Furthermore, the multifunction ACMS exhibited superior SERS capability with a detection limit (LOD) of 4.309 × 10−2 μg L−1 for MG residues in water. And the ACMS substrates could be utilized to determine the MG residues in crucian carp extract, resulting in a recovery rate of 96.00~116.00%. In addition, such multifunction heterojunctions were performed for in situ monitoring of the photodegradation process. This research opened up a novel perspective on the applications of heterojunction-based multifunction materials for food safety control. Full article
(This article belongs to the Section Environmental Separations)
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20 pages, 5490 KiB  
Article
Development of an Ultrasound-Assisted Emulsification Microextraction Method for the Determination of Volatile Compounds in Wines
by Ioanna Chalvantzi, Aspasia Nisiotou, Georgios Banilas and Athanasios Mallouchos
Separations 2023, 10(10), 525; https://doi.org/10.3390/separations10100525 - 27 Sep 2023
Cited by 1 | Viewed by 1310
Abstract
A fast and simple method based on ultrasound-assisted emulsification microextraction (USAEME) was developed for the analysis of volatile compounds in wines. A full factorial 24 screening design was built to investigate the main factors affecting the extraction of volatile components, namely the [...] Read more.
A fast and simple method based on ultrasound-assisted emulsification microextraction (USAEME) was developed for the analysis of volatile compounds in wines. A full factorial 24 screening design was built to investigate the main factors affecting the extraction of volatile components, namely the volume of extraction solvent, sonication time, salt content, and pH. Then, the factors with significant effects were optimized using an I-optimal design. The optimal value for all the variables studied was reached under the following experimental conditions: volume of extraction solvent 200 μL and salt content 5% m/v. The suitability of the optimized method was evaluated, resulting in very good linearity with coefficients of determination (R2) higher than 0.995 in all cases, while repeatability was lower than 8.4% except for d-limonene and p-cymene. Recoveries higher than 82% were observed for the groups of ethyl esters, acetate esters, alcohols, and terpenoid alcohols (linalool, α-terpineol). The recovery of acids ranged from 70.5% to 88.9%, whereas the three monoterpenes studied (d-limonene, γ-terpinene, p-cymene) were not extracted satisfactorily. The proposed method was effectively applied for the analysis of volatile compounds in laboratory-scale fermentations with selected strains of Saccharomyces cerevisiae. Full article
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27 pages, 465 KiB  
Review
Organic Solvent Nanofiltration and Data-Driven Approaches
by Pieter-Jan Piccard, Pedro Borges, Bart Cleuren, Jef Hooyberghs and Anita Buekenhoudt
Separations 2023, 10(9), 516; https://doi.org/10.3390/separations10090516 - 19 Sep 2023
Viewed by 1470
Abstract
Organic solvent nanofiltration (OSN) is a membrane separation method that has gained much interest due to its promising ability to offer an energy-lean alternative for traditional thermal separation methods. Industrial acceptance, however, is held back by the slow process of membrane screening based [...] Read more.
Organic solvent nanofiltration (OSN) is a membrane separation method that has gained much interest due to its promising ability to offer an energy-lean alternative for traditional thermal separation methods. Industrial acceptance, however, is held back by the slow process of membrane screening based on trial and error for each solute-solvent couple to be separated. Such time-consuming screening is necessary due to the absence of predictive models, caused by a lack of fundamental understanding of the complex separation mechanism complicated by the wide variety of solute and solvent properties, and the importance of all mutual solute-solvent-membrane affinities and competing interactions. Recently, data-driven approaches have gained a lot of attention due to their unprecedented predictive power, significantly outperforming traditional mechanistic models. In this review, we give an overview of both mechanistic models and the recent advances in data-driven modeling. In addition to other reviews, we want to emphasize the coherence of all mechanistic models and discuss their relevance in an increasingly data-driven field. We reflect on the use of data in the field of OSN and its compliance with the FAIR principles, and we give an overview of the state of the art of data-driven models in OSN. The review can serve as inspiration for any further modeling activities, both mechanistic and data-driven, in the field. Full article
(This article belongs to the Collection State of the Art in Separation Science)
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19 pages, 17398 KiB  
Article
Extraction of Gallium from the Brown Corundum Dust with a One-Step Alkaline Leaching Process
by Juhua Zhang, Cong Gao, Xujie Hui and Yuwei Chang
Separations 2023, 10(9), 510; https://doi.org/10.3390/separations10090510 - 15 Sep 2023
Viewed by 1457
Abstract
Brown corundum dust, which is created during the manufacturing of brown corundum using bauxite as the raw material, is a vital carrier of gallium. To ascertain the presence of the contained gallium, the brown corundum dust was measured and characterized (XRF, XRD, ICP-OES, [...] Read more.
Brown corundum dust, which is created during the manufacturing of brown corundum using bauxite as the raw material, is a vital carrier of gallium. To ascertain the presence of the contained gallium, the brown corundum dust was measured and characterized (XRF, XRD, ICP-OES, EPMA, SEM-EDS, etc.). Gallium was extracted from the brown corundum dust using a one-step alkali leaching process, and thermodynamic calculations were utilized to assess the viability of the leaching reactions. The effects of leaching parameters (NaOH solution concentration, leaching time, leaching temperature, solid–liquid ratio and stirring speed) on the recovery of gallium during the leaching process were investigated. A gallium recovery of 96.83% was discovered to be possible with the following parameters: 200 g/L of NaOH, 363 K for the leaching temperature, 60 min for the leaching time, 1:10 g/mL for the solid–liquid ratio, and 850 rpm for the stirring rate. Gallium extraction was negatively impacted by raising the leaching temperature above 363 K and the concentration of NaOH solution above 200 g/L due to the accelerated side reactions between Na+, K+, SiO44− and AlO2, which led to the precipitation of aluminosilicates that absorbed gallium from the solution. The influences of leaching parameters such as the temperature, NaOH solution concentration, and solid–liquid ratio on the leaching kinetics were examined. It was demonstrated that the leaching process followed the unreacted shrinking core model, that the interfacial diffusion associated with the contacting surface area served as the controlling step, and that the apparent activation energy was 42.83 kJ/mol. It turned out that the final kinetic equation was 1/(1 − α)1/3 − 1 = 4.34 × 104 × (CNaOH)2.12 (L/S)0.43exp[−42835/(RT)] t. Full article
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16 pages, 6007 KiB  
Article
Enhanced CO2 Capture by Sorption on Electrospun Poly (Methyl Methacrylate)
by Michele Ciulla, Valentino Canale, Rafal D. Wolicki, Serena Pilato, Pantaleone Bruni, Stefania Ferrari, Gabriella Siani, Antonella Fontana and Pietro Di Profio
Separations 2023, 10(9), 505; https://doi.org/10.3390/separations10090505 - 14 Sep 2023
Cited by 1 | Viewed by 1163
Abstract
Poly(methyl methacrylate) (PMMA) is characterized by high CO2 capture yield under mild pressures and temperatures. A morphological modification of powdery amorphous PMMA (pPMMA) is carried out by electrospinning to increase the surface/volume ratio of the resulting electrospun PMMAs (ePMMAs). This modification improves [...] Read more.
Poly(methyl methacrylate) (PMMA) is characterized by high CO2 capture yield under mild pressures and temperatures. A morphological modification of powdery amorphous PMMA (pPMMA) is carried out by electrospinning to increase the surface/volume ratio of the resulting electrospun PMMAs (ePMMAs). This modification improves the kinetics and the capture yields. The rate constants observed for ePMMAs are two to three times higher than those for pPMMA, reaching 90% saturation values within 5–7 s. The amount of sorbed CO2 is up to eleven times higher for ePMMAs at 1 °C, and the highest difference in captured CO2 amount is observed at the lowest tested pressure of 1 MPa. The operating life of the ePMMAs shows a 5% yield loss after ten consecutive runs, indicating good durability. Spent electrospun PMMAs after several cycles of CO2 sorption-desorption can be regenerated by melting and again electrospinning the molten mass, resulting in a CO2 capture performance that is undistinguishable from that observed with fresh ePMMA. Scanning electron and atomic force microscopies show a reduction in surface roughness after gas exposure, possibly due to the plasticization effect of CO2. This study shows the potential of electrospun PMMAs as solid sorbents for carbon capture from natural gas or pre-combustion and oxyfuel combustion processes. Full article
(This article belongs to the Special Issue Green Solvents and Advanced Materials for Gas Capture and Separation)
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17 pages, 2125 KiB  
Article
Comprehensive Profiling of Terpenes and Terpenoids in Different Cannabis Strains Using GC × GC-TOFMS
by Jasmeen Kaur, Ning Sun and Jane E. Hill
Separations 2023, 10(9), 500; https://doi.org/10.3390/separations10090500 - 13 Sep 2023
Cited by 1 | Viewed by 3075
Abstract
Cannabis contains a wide range of terpenes and terpenoids that are mainly responsible for their distinctive aroma and flavor. These compounds have also demonstrated therapeutic effects either alone and/or as synergistic compounds with other terpenes, terpenoids, and/or cannabinoids. Several studies have attempted to [...] Read more.
Cannabis contains a wide range of terpenes and terpenoids that are mainly responsible for their distinctive aroma and flavor. These compounds have also demonstrated therapeutic effects either alone and/or as synergistic compounds with other terpenes, terpenoids, and/or cannabinoids. Several studies have attempted to fully characterize terpenes and terpenoids in cannabis; however, most of these studies used one-dimensional gas chromatography, which often results in the co-elution of the compounds. In the present study, we analyzed terpenes and terpenoids in the dried flowers of six cannabis strains using a two-dimensional gas chromatograph time-of-flight mass spectrometer (GC × GC-TOFMS). A total of 146 terpenes and terpenoids were detected across all six cannabis strains with an enhanced separation of 16 terpenes and terpenoids in the second dimension. Additionally, we achieved enhanced separation of four terpenes and terpenoids from a standard mixture in the second dimension. Chemical differences were observed in the number and relative abundance of monoterpenes, monoterpenoids, sesquiterpenes, and sesquiterpenoids in all six strains. We were also able to identify four new terpenoids in cannabis, which are reported here for the first time. Full article
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37 pages, 2331 KiB  
Article
An In-Depth Stability Study of the Essential Oils from Mentha × piperita, Mentha spicata, Origanum vulgare, and Thymus vulgaris: The Impact of Thermal and Storage Conditions
by Eugenia Ganosi, Christina Barda, Maria-Eleni Grafakou, Michael Ch. Rallis and Helen Skaltsa
Separations 2023, 10(9), 488; https://doi.org/10.3390/separations10090488 - 7 Sep 2023
Viewed by 1363
Abstract
In recent years, there has been a growing scientific interest in essential oils due to their therapeutic and aromatic properties and as potential alternative natural additives for use as preservatives or antibiotics. However, the literature lacks a comprehensive understanding of their stability and [...] Read more.
In recent years, there has been a growing scientific interest in essential oils due to their therapeutic and aromatic properties and as potential alternative natural additives for use as preservatives or antibiotics. However, the literature lacks a comprehensive understanding of their stability and how their composition and properties change over time under various conditions. Through this paper, we aim to enhance the existing literature by providing deeper insights into the stability of essential oils and the sustainability of chemical composition in a time-based approach under various conditions. Therefore, four essential oils of the Lamiaceae family (Origanum vulgare, Thymus vulgaris, Mentha spicata, and M. x piperita) were evaluated with respect to their chemical variation influenced by several factors, such as thermal and storage conditions. Three types of containers were utilized to store the essential oils, i.e., glass ampoules, glass tubes, and metallic containers with plastic caps, for up to six months in −20 °C, 4 °C, 23 °C (with or without light exposure), 35 °C, and 45 °C. Samples were routinely analyzed by GC-MS and components were subjected to principal component analysis to ascertain whether the identified constituents may be useful in reflecting the stability of the analyzed samples. The main compounds appeared to be more stable, while the degradation of minor constituents (<1.0%) occurred in all four essential oils despite the storage conditions. Overall, apart from a slight variation in the chemical load, essential oils can be considered stable for various applications, especially those stored under low oxygen availability conditions. Full article
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24 pages, 697 KiB  
Review
Carnosic Acid and Carnosol: Analytical Methods for Their Determination in Plants, Foods and Biological Samples
by Christiana Mantzourani, Petros A. Tarantilis and Maroula G. Kokotou
Separations 2023, 10(9), 481; https://doi.org/10.3390/separations10090481 - 2 Sep 2023
Cited by 1 | Viewed by 3207
Abstract
Among the various phytochemicals, which are present in Lamiaceae plants, carnosic acid and carnosol stand out. Carnosic acid is a phenolic diterpene carrying two phenolic hydroxyl groups and a carboxyl group, while carnosol carries a lactone moiety in addition to phenolic hydroxyls. Both [...] Read more.
Among the various phytochemicals, which are present in Lamiaceae plants, carnosic acid and carnosol stand out. Carnosic acid is a phenolic diterpene carrying two phenolic hydroxyl groups and a carboxyl group, while carnosol carries a lactone moiety in addition to phenolic hydroxyls. Both these phenolic diterpenes exhibit interesting biological properties, such as antioxidant, anticancer, anti-inflammatory and neuroprotective activities. In this review, we summarize the existing analytical methods for the determination of carnosic acid and carnosol, primarily in plants, but also in foods and biological samples. Due to the biological importance of carnosic acid and carnosol, a variety of analytical methods, including high-performance liquid chromatography–ultra violet (HPLC–UV), liquid chromatography–mass spectrometry (LC–MS) and capillary electrophoresis (CE), were developed for their determination. In addition, we discuss the extraction methods applied for their isolation from plants and in brief the bioactivities of these phytochemicals. Full article
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19 pages, 5711 KiB  
Article
Carob Pulp Flour Extract Obtained by a Microwave-Assisted Extraction Technique: A Prospective Antioxidant and Antimicrobial Agent
by Jana Zahorec, Dragana Šoronja-Simović, Sunčica Kocić-Tanackov, Sandra Bulut, Nikola Martić, Katarina Bijelić, Danica Božović and Branimir Pavlić
Separations 2023, 10(9), 465; https://doi.org/10.3390/separations10090465 - 24 Aug 2023
Viewed by 1142
Abstract
In this study, carob pulp flour (CF) extract was characterized as a high-value antioxidant and antimicrobial agent. CF extracts were obtained using microwave-assisted extraction (MAE) and optimization of the MAE process was accomplished using response surface methodology. The studied processing parameters of MAE [...] Read more.
In this study, carob pulp flour (CF) extract was characterized as a high-value antioxidant and antimicrobial agent. CF extracts were obtained using microwave-assisted extraction (MAE) and optimization of the MAE process was accomplished using response surface methodology. The studied processing parameters of MAE were the liquid/solid (L/S) ratio (10–30 mL/g), extraction time (15–35 min), and ethanol concentration (40–80% w/w). The efficiency of the extraction of valuable compounds from CF was evaluated by the determining extraction yield (Y), total phenolic(TP), total flavonoid (TF) content, and antioxidant activity (DPPH, FRAP, and ABTS). The optimized MAE parameters for maximizing the yields of target compounds and antioxidant activity were the L/S ratio 30 mL/g, extraction time 35 min, and ethanol concentration 40%. The experimentally obtained values for TP, TF, DPPH, FRAP, and ABTS were 1609.92 GAE/100 g, 271.92 CE/100 g, 99.02 µMTE/g, 50.45 µM Fe2+/g, and 110.55 µMTE/g, respectively. The optimized CF extract was compared with the CF extracts obtained by conventional solid–liquid extraction (S/L) and ultrasound-assisted extraction (UAE) and was found to be more beneficial due to a 30% higher yield of TP and TF and 30–80% higher antioxidant activity. The phenolic profiles of the three extracts were quite similar. The microdilution method confirmed the antibacterial activity of MAE and S/L extracts while the antifungal effect was not observed. Full article
(This article belongs to the Special Issue Novel Applications of Separation Technology)
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19 pages, 3311 KiB  
Article
Potential Use of Agricultural Waste—Carob Kibbles (Ceratonia siliqua L.) as a Biosorbent for Removing Boron from Wastewater
by Luz Adriana Díaz, Jorge Dias Carlier, Izabela Michalak and María Clara Costa
Separations 2023, 10(9), 464; https://doi.org/10.3390/separations10090464 - 24 Aug 2023
Viewed by 1282
Abstract
The release of boron (B) into the environment as a result of anthropogenic activity modifies sustainable natural conditions, thus affecting ecosystems. To meet water quality regulations, commercial and natural boron adsorbents are available to reduce its concentrations in industrial effluents, with the former [...] Read more.
The release of boron (B) into the environment as a result of anthropogenic activity modifies sustainable natural conditions, thus affecting ecosystems. To meet water quality regulations, commercial and natural boron adsorbents are available to reduce its concentrations in industrial effluents, with the former being not only more expensive but also less sustainable. In the publication, the biosorption parameters of carob kibbles (Ceratonia siliqua L.) were optimized in order to remove boron from aqueous solutions using batch experiments. The biosorbent used in the present research was agro-waste biomass provided by the local locust-beam gum industry. Boron removal by carob kibbles was favored at high initial pH values, and this capacity was found to be a function of boron initial concentration, biosorbent content in the solution, and particle size. The change in temperature did not affect the potential of biomass to remove boron. The highest boron removal efficiency (55.1%) was achieved under the following optimal conditions: 50 g/L biosorbent dose (Cs), with particle size range 0.025–0.106 mm, for the initial concentration (C0) of boron in the solution of 100 mg/L, at an initial pH of 11.5, for 5 h at 25 °C. This investigation suggests that carob kibble agro-waste can be valorized as a biosorbent to remove boron from wastewater, and the boron-loaded residue may eventually be explored as a new boron-fertilizer. Full article
(This article belongs to the Special Issue (Bio)-Sorbents for Water Treatment and Soil Remediation)
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22 pages, 7059 KiB  
Review
Fluoride Removal from Water Sources by Adsorption on MOFs
by Athanasia K. Tolkou and Anastasios I. Zouboulis
Separations 2023, 10(9), 467; https://doi.org/10.3390/separations10090467 - 24 Aug 2023
Cited by 5 | Viewed by 1845
Abstract
Fluoride is present in several groundwaters due to natural or anthropogenic origins. Although it is necessary for physiological human functions (in small amounts, i.e., 0.5–1.2 mg/L), it could be very harmful when it exceeds the maximum permissible concentration limit of 1.5 mg/L (according [...] Read more.
Fluoride is present in several groundwaters due to natural or anthropogenic origins. Although it is necessary for physiological human functions (in small amounts, i.e., 0.5–1.2 mg/L), it could be very harmful when it exceeds the maximum permissible concentration limit of 1.5 mg/L (according to WHO). Among the numerous technologies for removing fluoride from waters, metal–organic framework (MOF) materials are considered to be promising adsorbents due to their advantages of high porosity, high specific surface area, diverse functions and easy modification. In this study, the synthesis of MOFs and the progress of their application to the removal of fluoride from contaminated water, as published in the recent literature mainly over the past five years, are reviewed. The adsorption mechanism(s) and its main characteristics, such as effect of initial fluoride concentration, adsorbent dosage, solution pH, contact time, adsorption capacity, thermodynamic and regeneration studies, etc., for the removal of fluoride with the addition of different MOFs are compared. According to these comparisons, the hydrothermal/solvothermal synthesis method is most commonly used for the preparation of MOFs, whereas higher BET surface areas are shown by specific MOFs based on aluminum metal ions. The main fluoride adsorption mechanisms were found to be electrostatic attraction and/or complexation. The most common pH for conducting experiments was 7.0, but several examined materials were found to be effective over a wide pH range. Four to six regeneration cycles were successfully applied on average, regarding the MOFs under review, whereas in the majority of these cases, the sorption process was found to be endothermic. Full article
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22 pages, 1095 KiB  
Review
Adsorption-Based Pretreatment of Irrigation Water to Prevent Water Quality Issues
by Tamás Kucserka, Gábor István Németh, Ivett Pálfi, Zsolt L. Kiss, Etelka Tombácz and Ildikó Galambos
Separations 2023, 10(9), 468; https://doi.org/10.3390/separations10090468 - 24 Aug 2023
Cited by 1 | Viewed by 1441
Abstract
Access to and the use of irrigation water of adequate quality and targeted nutrient supplementation have become more widespread in recent years. Both crop quality and the irrigation system lifetime are affected by the quality of the water used for irrigation. Micro-irrigation (e.g., [...] Read more.
Access to and the use of irrigation water of adequate quality and targeted nutrient supplementation have become more widespread in recent years. Both crop quality and the irrigation system lifetime are affected by the quality of the water used for irrigation. Micro-irrigation (e.g., drip and sprinkle) is becoming increasingly common alongside the more typical irrigation methods, but it requires expertise and pre-treatment to ensure a proper water supply. The most significant problem is clogging, which can greatly reduce irrigation efficiency. Treatment for irrigation purposes mainly depends on the contaminants that are present in the water. The main treatment options available are biological, electromagnetic and electrostatic treatments, but these have a wide range of effectiveness levels compared to membrane separation technologies. In addition, adsorption treatments are also available, which, depending on the adsorbent used, can greatly improve the pre-treatment of irrigation water. This work provides an overview of adsorbents suitable for the treatment of irrigation water and their effectiveness. The separation of interfering components via adsorption is effective and promising for future application as the expected irrigation demands increase. Full article
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17 pages, 800 KiB  
Article
Solid–Liquid Extraction of Bioactive Molecules from White Grape Skin: Optimization and Near-Infrared Spectroscopy
by Tea Sokač Cvetnić, Korina Krog, Maja Benković, Tamara Jurina, Davor Valinger, Jasenka Gajdoš Kljusurić, Ivana Radojčić Redovniković and Ana Jurinjak Tušek
Separations 2023, 10(8), 452; https://doi.org/10.3390/separations10080452 - 14 Aug 2023
Viewed by 1117
Abstract
In this work, the solid–liquid extraction of bioactive molecules from grape skin was performed using water as the extraction solvent. The effects of extraction time (t = 60, 75, and 90 min), extraction temperature (T = 40, 60, and 80 °C), [...] Read more.
In this work, the solid–liquid extraction of bioactive molecules from grape skin was performed using water as the extraction solvent. The effects of extraction time (t = 60, 75, and 90 min), extraction temperature (T = 40, 60, and 80 °C), solid–liquid phase ratio (S/L = 10, 20, and 30 g/L), and mixing speed (rpm = 250, 500, and 750 1/min) on the total dissolved solids, extraction yield, concentration of total polyphenols, and antioxidant activity were determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. According to response surface modeling, the optimal extraction conditions were t = 75 min, T = 80 °C, S/L = 30 g/L, and rpm = 750 1/min, and under optimal process conditions, 8.38 mgGAE/gd.m. was obtained. Furthermore, the potential of near-infrared (NIR) spectroscopy coupled with artificial neural network (ANN) modeling for prediction of the physical and chemical properties of prepared extracts was also analyzed. The use of ANN modeling demonstrated highly favorable correlations between the NIR spectra and all the variables tested, particularly the total dissolved solids (TDS) and antioxidant activity measured using the FRAP method. As a result, ANN modeling proved to be a valuable tool for predicting the concentration of total polyphenols, the antioxidant activity, and the extraction yield of a plant extract based on its NIR spectra. Full article
(This article belongs to the Section Bioanalysis/Clinical Analysis)
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18 pages, 1141 KiB  
Article
The Development and Validation of a Targeted LC-HRAM-MS/MS Methodology to Separate and Quantify p-Synephrine and m-Synephrine in Dietary Supplements and Herbal Preparations
by Celine Vanhee, Sophia Barhdadi, Angélique Kamugisha, Tanika Van Mulders, Kevin Vanbrusselen, Marie Willocx and Eric Deconinck
Separations 2023, 10(8), 444; https://doi.org/10.3390/separations10080444 - 9 Aug 2023
Cited by 1 | Viewed by 1206
Abstract
Dietary supplements containing Citrus aurantium or p-synephrine remain very popular in Europe and the United States of America (USA). They are primarily sold as weight loss enhancers, although their efficacy and the safety are still under scrutiny. To this end, several countries [...] Read more.
Dietary supplements containing Citrus aurantium or p-synephrine remain very popular in Europe and the United States of America (USA). They are primarily sold as weight loss enhancers, although their efficacy and the safety are still under scrutiny. To this end, several countries have set maximum threshold levels of p-synephrine that are permitted in dietary supplements. Moreover, there have also been reports of possible chemical adulteration of these supplements with the synthetic positional isomer, m-synephrine, known to be used as a medicinal product. Therefore, it is pivotal for regulatory agencies to be able to discriminate between the two positional isomers and also quantify the amount of each when encountered in dietary supplements. Here, we present the development and the validation of a simple and fast “dilute and shoot” procedure, employing liquid chromatographic (LC) separation in combination with high-resolution accurate mass (HRAM) tandem mass spectroscopy (LC-HRAM-MS/MS) to separate these two isomers and subsequently quantify them. The quantification methodology has been validated using the “total error approach”, applying accuracy profiles, and is consequently compliant with ISO17025. Moreover, ten real-life samples, either purchased online or encountered by Belgian regulatory agencies, were analyzed using the described procedure. Startlingly, only one sample out of ten was compliant with Belgian legislation in terms of labeling, the presence of a batch number, expiration date and dosage (with a tolerated error of ±20%). Moreover, three samples also contained banned substances such as yohimbine and sibutramine. Full article
(This article belongs to the Special Issue Recent Advances and Trends in Dietary Supplement Analysis)
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24 pages, 4875 KiB  
Article
Biosynthesis of Salbutamol-4′-O-sulfate as Reference for Identification of Intake Routes and Enantiopure Salbutamol Administration by Achiral UHPLC-MS/MS
by Annika Lisa Jendretzki, Lukas Corbinian Harps, Yanan Sun, Felix Bredendiek, Matthias Bureik, Ulrich Girreser, Xavier de la Torre, Francesco M. Botrè and Maria Kristina Parr
Separations 2023, 10(8), 427; https://doi.org/10.3390/separations10080427 - 28 Jul 2023
Cited by 1 | Viewed by 1698
Abstract
The aim of the study was a comprehensive and quantitative determination of salbutamol and its sulfoconjugated major metabolite in urine samples using achiral ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Therefore, salbutamol-4′-O-sulfate was biosynthesized as a reference using genetically modified fission [...] Read more.
The aim of the study was a comprehensive and quantitative determination of salbutamol and its sulfoconjugated major metabolite in urine samples using achiral ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Therefore, salbutamol-4′-O-sulfate was biosynthesized as a reference using genetically modified fission yeast cells, and the product was subsequently characterized by NMR and HRMS. In competitive sports, salbutamol is classified as a prohibited drug; however, inhalation at therapeutic doses is permitted with a maximum allowance of 600 µg/8 h. In contrast, the enantiopure levosalbutamol is prohibited under any condition. For analytical discrimination, the amount of salbutamol and its main metabolite excreted in the urine was studied. As proof of concept, a longitudinal study in one healthy volunteer was performed in order to investigate excreted amounts and to study potential discrimination using achiral chromatography. Discrimination of administration of racemic salbutamol or the enantiopure levosalbutamol was not achieved by solely analyzing salbutamol as the parent compound. However, a distinction was possible by evaluation of the proportion of salbutamol-4′-O-sulfate in relation to salbutamol. Therefore, reference material of metabolites is of great importance in doping control, especially for threshold substances. Full article
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19 pages, 1119 KiB  
Article
Phytochemical Profile, Antioxidant Activity and Cholinesterase Inhibition Potential of Essential Oil and Extracts of Teucrium montanum from Bosnia and Herzegovina
by Mejra Bektasevic, Mladenka Jurin, Marin Roje and Olivera Politeo
Separations 2023, 10(8), 421; https://doi.org/10.3390/separations10080421 - 26 Jul 2023
Cited by 7 | Viewed by 1478
Abstract
Bioactive compounds from plants play an important role in slowing many neurodegenerative diseases, such as Alzheimer’s disease, by inhibiting cholinesterase enzymes. Studies have shown that oxidative stress is associated with the development of Alzheimer’s disease. In traditional medicine of Bosnia and Herzegovina, Teucrium [...] Read more.
Bioactive compounds from plants play an important role in slowing many neurodegenerative diseases, such as Alzheimer’s disease, by inhibiting cholinesterase enzymes. Studies have shown that oxidative stress is associated with the development of Alzheimer’s disease. In traditional medicine of Bosnia and Herzegovina, Teucrium montanum is used to treat numerous diseases. The chemical composition and biological activity of the essential oil (EO) and aqueous (AE) and methanol extract (ME) of this plant were studied. The chemical composition of EO was studied using GC-MS, while the composition of the extracts was studied using HPLC-DAD. Antioxidant activity was tested using the DPPH and FRAP methods. The protection of lipids and proteins from oxidation was tested using the ammonium thiocyanate and BSA oxidation methods. The ability to inhibit cholinesterases was tested by the Ellman method. The main identified EO compounds were α-cadinol, ß-selinene, δ-cadinene, epi-α-cadinol, germacrene D-4-ol, and α-pinene. The main phenolic compounds of the extracts were p-coumaric acid, ellagic acid and caffeic acid. The tested extracts showed good antioxidant radical scavenging and reducing potential and a very good ability to protect lipids and proteins from oxidation. The EO showed moderate AChE and BChE inhibition potential, while the extracts showed weak or no ability. Full article
(This article belongs to the Special Issue Separation, Analysis and Biological Evaluation of Bioactive Compounds)
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18 pages, 3155 KiB  
Review
Advances in Cork Use in Adsorption Applications: An Overview of the Last Decade of Research
by João Jesus, Raquel Nunes da Silva and Ariana Pintor
Separations 2023, 10(7), 390; https://doi.org/10.3390/separations10070390 - 3 Jul 2023
Cited by 2 | Viewed by 2000
Abstract
Cork-based adsorbents have been gathering interest from the research community since the 1990s. A first review was published on this topic in 2012. Still, in the last decade, novel activated carbons and biochars, in multiple applications, have been produced using cork as a [...] Read more.
Cork-based adsorbents have been gathering interest from the research community since the 1990s. A first review was published on this topic in 2012. Still, in the last decade, novel activated carbons and biochars, in multiple applications, have been produced using cork as a raw material. This review presents these novel insights into the properties of cork, in its various forms, and how they relate to adsorption capacity. Details on new preparation methodologies and respective characteristics of cork-based activated carbons and biochars are thoroughly compared, and patterns are identified. Finally, the adsorption capacity of these materials in experimental conditions is reviewed for different compounds: heavy metals, organics, and gaseous pollutants. This review provides a complete picture of the kind and quality of different cork forms, their relative economic value, and how their conversion into activated carbons and biochars can contribute to a more circular economy by producing adsorbents that aid in the reduction of multiple pollution types. Full article
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23 pages, 2691 KiB  
Article
Quantitation of Formoterol, Salbutamol, and Salbutamol-4′-O-Sulfate in Human Urine and Serum via UHPLC-MS/MS
by Lukas C. Harps, Daniel A. Bizjak, Ulrich Girreser, Martina Zügel, Jürgen M. Steinacker, Patrick Diel and Maria Kristina Parr
Separations 2023, 10(7), 368; https://doi.org/10.3390/separations10070368 - 22 Jun 2023
Cited by 1 | Viewed by 1292
Abstract
The adrenergic beta-2 agonists formoterol and salbutamol are used for the treatment of asthma and COPD but are also misused in sports competitions. Therefore, they are included in WADA regulations. Both drugs are mainly excreted in urine after administration via inhalation. A four-armed, [...] Read more.
The adrenergic beta-2 agonists formoterol and salbutamol are used for the treatment of asthma and COPD but are also misused in sports competitions. Therefore, they are included in WADA regulations. Both drugs are mainly excreted in urine after administration via inhalation. A four-armed, double-blind cross-over clinical trial was conducted involving endurance-trained participants (12 females and 12 males). Inhalation dosages of 36 μg formoterol, 1200 μg salbutamol, a combination of both, or a placebo were administered before exercise. Serum and urine were collected after exercise and 3 and 24 h after administration. Here, we show the successful quantitation of formoterol, salbutamol, and its phase II metabolite salbutamol-4′-O-sulfate in all urine and serum samples using ultra-high performance liquid chromatography–tandem mass spectrometry. In the serum analysis, results of up to 14.2 pg/mL formoterol, 10.0 ng/mL salbutamol, and 21.4 ng/mL salbutamol-4′-O-sulfate (calculated as salbutamol equivalent) were found. In urine, maximum concentrations (after deglucuronidation) were 17.2 ng/mL formoterol, 948.5 ng/mL salbutamol, and 2738.5 ng/mL salbutamol-4′-O-sulfate. Sex-specific differences in serum concentrations as well as in urinary excretion were observed. The results pronounce the importance of the implementation and elucidation of phase II metabolites to quantitation methods in antidoping. Full article
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17 pages, 1837 KiB  
Article
Comprehensive Metabolite Fingerprinting of Australian Black and Green Olives and Their Antioxidant and Pharmacokinetics Properties
by Akhtar Ali, Farhad Ahmadi, Jeremy J. Cottrell and Frank R. Dunshea
Separations 2023, 10(6), 354; https://doi.org/10.3390/separations10060354 - 13 Jun 2023
Cited by 5 | Viewed by 2038
Abstract
Polyphenols, especially flavonoids, are well-known for their bioactive antioxidant properties. Therefore, this study aimed to analyze Australian black (ripe) and green olives (unripe) for phenolic and non-phenolic metabolites, antioxidant activities, and pharmacokinetic properties. Liquid chromatography–mass spectrometry coupled with quadrupole–time of flight (LC–ESI–QTOF–MS/MS) was [...] Read more.
Polyphenols, especially flavonoids, are well-known for their bioactive antioxidant properties. Therefore, this study aimed to analyze Australian black (ripe) and green olives (unripe) for phenolic and non-phenolic metabolites, antioxidant activities, and pharmacokinetic properties. Liquid chromatography–mass spectrometry coupled with quadrupole–time of flight (LC–ESI–QTOF–MS/MS) was applied to elucidate the composition, identification, and characterization of bioactive metabolites from Australian olives. This study identified 110 metabolites, including phenolic acids, flavonoids, stilbenes, lignans, and other compounds (phenolic terpenes, tyrosols, fatty acids, and terpenoids). Luteolin (flavonoid) and verbascoside (hydroxycinnamic acid) are identified with higher concentrations in black olives. Black (ripe) olives were measured at a higher TPC (10.94 ± 0.42 mg GAE/g) and total antioxidant potential than green olives. The pharmacokinetic properties (absorption, distribution, metabolism, excretion, toxicity) of phenolic compounds for human health were evaluated to predict the potential of the most abundant metabolites in olives. Gastrointestinal absorption and Caco-2 cell permeability of metabolites in olives were also predicted. This study will develop into further research to identify the Australian olives’ therapeutic, nutraceutical, and phytopharmaceutical potential. Full article
(This article belongs to the Special Issue Isolation, Elucidation and Synthesis of Bioactive Natural Products)
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17 pages, 1070 KiB  
Article
Particle Cut Diameter Prediction of Uniflow Cyclone Systems with Fuzzy System Analysis
by Vinzenz Klapper, Giovanni Luzi, Benedict Prah and Antonio Delgado
Separations 2023, 10(6), 345; https://doi.org/10.3390/separations10060345 - 5 Jun 2023
Cited by 1 | Viewed by 2069
Abstract
Cyclones are devices used in various industries to remove particulate matter from gases and liquids. Commonly used in the power generation, cement, and mining industries, cyclones improve the efficiency and longevity of equipment by removing dust and other small particles that can cause [...] Read more.
Cyclones are devices used in various industries to remove particulate matter from gases and liquids. Commonly used in the power generation, cement, and mining industries, cyclones improve the efficiency and longevity of equipment by removing dust and other small particles that can cause wear and damage. Among centrifugal separation, reverse-flow cyclones are primarily used for particle separation, which can reach heights of several meters on an industrial scale and therefore, are difficult to access for maintenance. A uniflow centrifugal segregation system avoids these drawbacks of reverse-flow cyclones since their accessibility is good and their height usually does not exceed their diameter. The efficiency is a critical aspect of separating systems. This study systematically examines the collection efficiency for particles ranging from 1 μm to 29 μm in diameter based on varying vane angles of the swirl inducer at flow rates ranging from 130 Ls1 to 236 Ls1. Full article
(This article belongs to the Collection Feature Paper Collection in Section 'Purification Technology')
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19 pages, 8233 KiB  
Article
Particulate Matter Detachment from a Magnetizable Single Fiber Applying Magnetic Forces in Ambient Air
by Julia Szabadi, Jörg Meyer and Achim Dittler
Separations 2023, 10(5), 297; https://doi.org/10.3390/separations10050297 - 7 May 2023
Cited by 2 | Viewed by 1242
Abstract
The potential utilization of magnetic effects in gas particle separation is a current subject of research. This paper demonstrates for the first time that a single magnetizable filter fiber can be deflected by a magnetically induced excitation for a selected combination of parameters, [...] Read more.
The potential utilization of magnetic effects in gas particle separation is a current subject of research. This paper demonstrates for the first time that a single magnetizable filter fiber can be deflected by a magnetically induced excitation for a selected combination of parameters, resulting in the removal of deposited particle structures with high detachment levels. A correlation between the magnetic flux density and achieved acceleration to overcome the adhesive forces/strength of the particle structure was determined. The degree of detachment after each regeneration was calculated by comparing the projection area before and after detachment using high-speed images. At a magnetic flux density of B = 38.5 mT, accelerations of maximum a = 105 m·s−2 are achieved, depending on the axial position along the single fiber. The degrees of regeneration achieved at these parameters depend on the amount of fiber loading and on the fiber orientation in the gravitational field. The horizontal orientation of the fiber leads to an increased reattachment of precedingly detached particle structures after deflection compared to a vertical orientation. High particle loading on the fiber results in enhanced detachment by inertia. Under the most favorable process conditions investigated, detachment levels of >90% are achieved. Full article
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23 pages, 3386 KiB  
Article
Comparative Study of Conventional, Microwave-Assisted and Supercritical Fluid Extraction of Bioactive Compounds from Microalgae: The Case of Scenedesmus obliquus
by Ioulia Georgiopoulou, Vasiliki Louli and Kostis Magoulas
Separations 2023, 10(5), 290; https://doi.org/10.3390/separations10050290 - 4 May 2023
Cited by 3 | Viewed by 2175
Abstract
The recovery of bioactive products with green processes is a critical topic for the research and industry fields. In this work, the application of solid–liquid (SLE), microwave-assisted extraction (MAE) with aq. ethanol 90% v/v and supercritical fluid extraction (SFE) with CO [...] Read more.
The recovery of bioactive products with green processes is a critical topic for the research and industry fields. In this work, the application of solid–liquid (SLE), microwave-assisted extraction (MAE) with aq. ethanol 90% v/v and supercritical fluid extraction (SFE) with CO2 for the recovery of biocomponents from Scenedesmus obliquus is studied. The effects examined were temperature (30–60 °C), time (6–24 h), and solvent-to-biomass ratio (20–90 mLsolv/gbiom) for SLE, temperature (40–60 °C), time (5–25 min), solvent-to-biomass ratio (20–90 mLsolv/gbiom), and microwave power (300–800 W) for MAE, and temperature (40–60 °C), pressure (110–250 bar), solvent flow rate (20–40 gsolv/min), and cosolvent presence (0, 10% w/w ethanol) for SFE in relation to the extract’s yield, phenolic, chlorophyll, carotenoid content, and antioxidant activity. The optimum extraction conditions determined were 30 °C, 24 h, and 90 mLsolv/gbiom for SLE, 60 °C, 5 min, 90 mLsolv/gbiom, and 300 W for MAE, and 60 °C, 250 bar, and 40 gsolv/min for SFE. Additionally, a kinetic SFE study was conducted and the obtained results were satisfactorily correlated using Sovová’s model. The comparison between the methods proved MAE’s efficiency in all terms compared to SLE. Moreover, SFE was accompanied with the lowest yield and chlorophyll content, yet led to an increased carotenoid content and improved antioxidant activity. Finally, the cosolvent addition significantly improved SFE’s yield and led to the most superior extract. Full article
(This article belongs to the Special Issue Separation, Extraction and Purification of Natural Products)
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19 pages, 4166 KiB  
Article
Improvement of Gd(III) Solvent Extraction by 4-Benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one: Non-Aqueous Systems
by Maria Atanassova and Rositsa Kukeva
Separations 2023, 10(5), 286; https://doi.org/10.3390/separations10050286 - 3 May 2023
Cited by 1 | Viewed by 1613
Abstract
The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C1Cnim+][Tf2N], n [...] Read more.
The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C1Cnim+][Tf2N], n = 4, 10) and CHCl3, as diluents. Compared to CHCl3, the ionic liquid offers increased distribution ratios in an aqueous medium. A step forward, enhanced solvent extraction, and improved separation upon the addition of ethylene glycol are demonstrated, i.e., a boost of two immiscible organic phases, compared to traditional aqueous solutions. However, this is noticeable when using CHCl3, but unfortunately not with ionic liquid combination, [C1C10im+][Tf2N]. Several conclusions are given, highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the chelating agent HP for various metal s-, p-, d-, and f-cations, i.e., nearly 25 metals. A detailed evaluation of the selectivity between these metals was made when changing both the aqueous phase completely with ethylene glycol or partially with glycerol (1:1). Electron paramagnetic resonance (EPR) spectroscopy has been used to study the established chemical species in the obtained organic extracts, such as Gd3+, Fe3+, Cu2+, and Cr3+, with unpaired electrons. Full article
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18 pages, 2583 KiB  
Article
Method Development and Validation for the Simultaneous Quantitation of Pentoxifylline, Its Pharmacologically Active Metabolites, and Donepezil Using LC-MS/MS in Rat Plasma: Its Application to a Pharmacokinetic Study
by Sanghee Choi, Wang-Seob Shim, Jiyoung Yoon, Doowon Choi, Eunseo Song, Yeo Jin Choi, Soo-Heui Paik and Kyung-Tae Lee
Separations 2023, 10(5), 276; https://doi.org/10.3390/separations10050276 - 24 Apr 2023
Cited by 1 | Viewed by 1548
Abstract
This study developed a simple, rapid, reproducible, and analytical method using liquid chromatography and electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify pentoxifylline (PTX), its pharmacological active metabolites, lisofylline (PTX-M1) and 1-(3-carboxypropyl)-3,7-dimethylxanthine (PTX-M5), and donepezil (DNP) in rat plasma, using [...] Read more.
This study developed a simple, rapid, reproducible, and analytical method using liquid chromatography and electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify pentoxifylline (PTX), its pharmacological active metabolites, lisofylline (PTX-M1) and 1-(3-carboxypropyl)-3,7-dimethylxanthine (PTX-M5), and donepezil (DNP) in rat plasma, using PTX-d6 and DNP-d7 as the internal standards. The LC-MS/MS procedure was performed at the ESI interface, operating in positive ionization and multiple reaction monitoring (MRM) modes; the monitoring of transitions comprised m/z 279.3 > 181.1 for PTX, m/z 281.1 > 263.1 > 160.90 for PTX-M1, m/z 267.1 > 249.0 > 220.9 for PTX-M5, m/z 380.3 > 90.9 for DNP, m/z 285.3 > 187.1 for PTX-d6 (IS1), and m/z 387.3 > 98.3 for DNP-d7 (IS2). After plasma protein precipitation (PP) with methanol, chromatographic separation was performed with an Imtakt Cadenza® CD-C18 (100 × 3 mm, 3 µm) column, using an isocratic mobile phase consisting of 0.1% formic acid in water and methanol (20:80, v/v) at a flow rate of 0.2 mL/min. The retention times of DNP, PTX-M5, PTX, and PTX-M1 were 2.24, 2.50, 2.68, and 2.72 min, respectively, with a total run time of 5 min. This method was validated over a linear concentration range of 5–8000, 10–5000, 20–15,000, and 2–500 ng mL−1 for PTX, PTX-M1, PTX-M5, and DNP, respectively, with a high correlation coefficient (r2 ≥ 0.99). The established method was fully validated in terms of selectivity, the lower limit of quantitation, precision, accuracy, recovery, matrix effect, stability, and dilution integrity according to the regulatory guidelines from the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. The validated method was successfully applied to a pharmacokinetic study on the concurrent administration of DNP and PTX in rats. Full article
(This article belongs to the Section Bioanalysis/Clinical Analysis)
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15 pages, 934 KiB  
Article
Cucumis metuliferus L. Fruits Extract with Antioxidant, Anti-Inflammatory, and Antidiabetic Properties as Source of Ursolic Acid
by Anna Cazanevscaia Busuioc, Giorgiana Valentina Costea, Andreea Veronica Dediu Botezatu, Bianca Furdui and Rodica Mihaela Dinica
Separations 2023, 10(5), 274; https://doi.org/10.3390/separations10050274 - 23 Apr 2023
Cited by 2 | Viewed by 1663
Abstract
To identify healthy, nutritious, and sustainable plant-based products rich in biologically active compounds, this present study was conducted, and the phytochemical composition and biological properties of the hydroethanolic ultrasound-assisted extract of the fruits of Cucumis metuliferus were investigated. Cucumis metuliferus is an unexplored [...] Read more.
To identify healthy, nutritious, and sustainable plant-based products rich in biologically active compounds, this present study was conducted, and the phytochemical composition and biological properties of the hydroethanolic ultrasound-assisted extract of the fruits of Cucumis metuliferus were investigated. Cucumis metuliferus is an unexplored fruit of a climbing plant in the Cucurbitaceae family, widely distributed in the tropical and subtropical regions of sub-Saharan Africa and whose nutritional and medicinal benefits are well known in African countries, especially. Therefore, its cultivation in other regions could influence chemical composition. The structural identification of the compounds from the hydroethanolic extract from Cucumis metuliferus fruits grown in Romania was carried out by chromatographic techniques (HPLC). The main compounds identified were catechin, oleanolic acid, ursolic acid, p-coumaric acid, and epicatechin. Subsequently, a method was proposed to isolate and characterize ursolic acid, one of the major compounds. The obtained results show that the hydroethanolic extract is rich in antioxidant compounds evaluated using the DPPH radical inhibition method (IC50 = 32.74 ± 0.02 µg/mL) and ABTS cation radical inhibition method (IC50 = 11.37 ± 0.07 µg/mL). It also demonstrate in vitro anti-inflammatory activities, such as anti-lipoxygenase (IC50 = 32.90 ± 0.05 µg/mL) and anti-proteinase (IC50 = 16.34 ± 0.07 µg/mL), and antidiabetic properties by inhibiting α-amylase (IC50 = 429.541 ± 0.25 µg/mL) and β-glucosidase activity (IC50 = 385.685 ± 0.76 µg/mL). Therefore, C. metuliferus fruits could be effectively used in the development of various health-promoting products, being not only appetizing, with spectacular appearance and with extended storage life, but also curative and healthy. Full article
(This article belongs to the Special Issue Separation, Extraction and Purification of Natural Products)
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30 pages, 3393 KiB  
Review
Mass Transfer and Droplet Behaviors in Liquid-Liquid Extraction Process Based on Multi-Scale Perspective: A Review
by Sicen Yu, Jiyizhe Zhang, Shaowei Li, Zhuo Chen and Yundong Wang
Separations 2023, 10(4), 264; https://doi.org/10.3390/separations10040264 - 18 Apr 2023
Cited by 3 | Viewed by 4844
Abstract
Liquid-liquid extraction is an important separation technology in the chemical industry, and its separation efficiency depends on thermodynamics (two-phase equilibrium), hydrodynamics (two-phase mixing and contact), and mass transfer (molecular diffusion). For hydrodynamics, the dispersion size of droplets reflects the mixing of two phases [...] Read more.
Liquid-liquid extraction is an important separation technology in the chemical industry, and its separation efficiency depends on thermodynamics (two-phase equilibrium), hydrodynamics (two-phase mixing and contact), and mass transfer (molecular diffusion). For hydrodynamics, the dispersion size of droplets reflects the mixing of two phases and determines the mass transfer contact area of the two phases. Therefore, a deep understanding of the droplet dispersion mechanism can help guide process intensification. The mass transfer and droplet behaviors in the liquid-liquid extraction process are reviewed based on three scales: equipment, droplets, and the interface between two liquids. Studies on the interaction between mass transfer and other performance parameters in extraction equipment as well as liquid-liquid two-phase flow models are reviewed at the equipment scale. The behaviors of droplet breakage and coalescence and the kernel function of the population balance equation are reviewed at the droplet scale. Studies on dynamic interfacial tension and interaction between interfaces are reviewed at the interface scale. Finally, the connection among each scale is summarized, the existing problems are analyzed, and some future research directions are proposed in the last section. Full article
(This article belongs to the Special Issue Advances in Separation Engineering)
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15 pages, 3373 KiB  
Article
Characterization and Photocatalytic Performance of Newly Synthesized ZnO Nanoparticles for Environmental Organic Pollutants Removal from Water System
by Vesna Despotović, Nina Finčur, Sabolč Bognar, Daniela Šojić Merkulov, Predrag Putnik, Biljana Abramović and Sanja Panić
Separations 2023, 10(4), 258; https://doi.org/10.3390/separations10040258 - 16 Apr 2023
Cited by 1 | Viewed by 1551
Abstract
Most countries are facing problems of environmental pollution due to toxic organic pollutants being discharged into the environment from various man-made sources. Heterogeneous photocatalysis is a possible solution for the mentioned problem, and it has been widely applied for the removal of pollutants [...] Read more.
Most countries are facing problems of environmental pollution due to toxic organic pollutants being discharged into the environment from various man-made sources. Heterogeneous photocatalysis is a possible solution for the mentioned problem, and it has been widely applied for the removal of pollutants from aqueous solutions, thanks to its high removal efficiency and environmental friendliness. Among the commonly used metal oxides, ZnO has attracted researchers’ interests due to its ecofriendly and nontoxic nature. In this work, ZnO nanoparticles (ZnO-NPs) were prepared by the precipitation method from water (w) and ethanol solutions of the corresponding metal precursors (zinc–acetate dihydrate, A_ZnO, and zinc–nitrate hexahydrate, N_ZnO) followed by calcination at different temperatures. The structure and morphology of the prepared catalysts were characterized by different techniques (XRD, BET, and SEM). Based on the XRD results, it can be seen that the synthesized NPs possess high purity. Furthermore, at a higher calcination temperature, a higher crystal size was observed, which was more intense in the case of the ethanol solution of the precursors. The BET analysis showed macropores at the surface and also indicated that the increased temperature led to decreased surface area. Finally, SEM images showed that in the case of the water precursor solution, an irregular, rod-like shape of the NPs was observed. The photocatalytic properties of newly synthesized ZnO-NPs exposed to simulated sunlight were examined during the removal of pesticide clomazone (CLO) and the antidepressant drug amitriptyline (AMI). ZnO-NPs prepared by the precipitation method from the water solution of zinc–acetate dihydrate and calcined at 500 °C (A_ZnOw_500) showed the highest performance under simulated sunlight. Furthermore, the activity of A_ZnOw_500 and N_ZnOw_500 catalysts in the removal of three organic pollutants from water—two pesticides (sulcotrione (SUL) and CLO) and one pharmaceutical (AMI)—was also compared. Results showed that decreased photocatalytic activity was observed in the presence of N_ZnOw_500 NPs in all investigated systems. Finally, the effect of the initial pH was also examined. It was found that in the case of CLO and SUL, there was no influence of the initial pH, while in the case of AMI the kapp was slightly increased in the range from pH ~7 to pH ~10. Full article
(This article belongs to the Section Environmental Separations)
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23 pages, 6194 KiB  
Article
Multidimensional Fractionation of Particles
by Uwe Frank, Jana Dienstbier, Florentin Tischer, Simon E. Wawra, Lukas Gromotka, Johannes Walter, Frauke Liers and Wolfgang Peukert
Separations 2023, 10(4), 252; https://doi.org/10.3390/separations10040252 - 13 Apr 2023
Cited by 2 | Viewed by 1556
Abstract
The increasing complexity in particle science and technology requires the ability to deal with multidimensional property distributions. We present the theoretical background for multidimensional fractionations by transferring the concepts known from one dimensional to higher dimensional separations. Particles in fluids are separated by [...] Read more.
The increasing complexity in particle science and technology requires the ability to deal with multidimensional property distributions. We present the theoretical background for multidimensional fractionations by transferring the concepts known from one dimensional to higher dimensional separations. Particles in fluids are separated by acting forces or velocities, which are commonly induces by external fields, e.g., gravitational, centrifugal or electro-magnetic fields. In addition, short-range force fields induced by particle interactions can be employed for fractionation. In this special case, nanoparticle chromatography is a recent example. The framework for handling and characterizing multidimensional separation processes acting on multidimensional particle size distributions is presented. Illustrative examples for technical realizations are given for shape-selective separation in a hydrocyclone and for density-selective separation in a disc separator. Full article
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17 pages, 1944 KiB  
Article
Salting-Out Assisted Liquid-Liquid Extraction for UPLC-MS/MS Determination of Thyroxine and Steroid Hormones in Human Serum and Fish Plasma
by Alemnesh Yirda Urge, Daniela Maria Pampanin, Maria Elena Martino, David Lausten Knudsen and Cato Brede
Separations 2023, 10(4), 240; https://doi.org/10.3390/separations10040240 - 5 Apr 2023
Cited by 2 | Viewed by 3116
Abstract
Measuring the level of steroid and thyroxine hormones is key to understanding organism health conditions. Liquid chromatography coupled with tandem mass spectrometry has become the method of choice for such hormone analyses in clinical laboratories. Detection of hormones at low levels typically requires [...] Read more.
Measuring the level of steroid and thyroxine hormones is key to understanding organism health conditions. Liquid chromatography coupled with tandem mass spectrometry has become the method of choice for such hormone analyses in clinical laboratories. Detection of hormones at low levels typically requires a time-consuming sample preparation, such as liquid-liquid extraction followed by solvent evaporation and re-solubilization of the sample extract. Instead, we applied salting-out assisted liquid-liquid extraction (SALLE) for the extraction of thyroxine, testosterone, cortisone, and cortisol from human serum and fish plasma samples. SALLE allowed direct injection of sample extracts. Sodium chloride and ammonium sulfate were evaluated as salting-out reagents together with four different organic solvents. High extraction recovery and reduced matrix interference were achieved by using ammonium sulfate together with 10% methanol in acetonitrile. Limits of quantification were in the range of 0.1–0.2 ng/mL and signal responses were linear (R2 > 0.997) up to at least 100 ng/mL for all hormones. The method was applied for hormone measurements in fish plasma. In conclusion, SALLE combines the simplicity of crude protein precipitation with the high analyte enrichment of a liquid-liquid extraction. Here we have presented it as a novel sample preparation method for clinical laboratories where mass spectrometry is utilized in the field of endocrinology. Full article
(This article belongs to the Special Issue Mass Spectrometry Development and Its Application in Bioanalysis)
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18 pages, 5932 KiB  
Article
Green-Engineered Barrier Creams with Montmorillonite-Chlorophyll Clays as Adsorbents for Benzene, Toluene, and Xylene
by Meichen Wang and Timothy D. Phillips
Separations 2023, 10(4), 237; https://doi.org/10.3390/separations10040237 - 4 Apr 2023
Cited by 6 | Viewed by 3953
Abstract
Dermal exposures to hazardous environmental chemicals in water can significantly affect the morphology and integrity of skin structure, leading to enhanced and deeper penetration. Organic solvents, such as benzene, toluene, and xylene (BTX), have been detected in humans following skin exposure. In this [...] Read more.
Dermal exposures to hazardous environmental chemicals in water can significantly affect the morphology and integrity of skin structure, leading to enhanced and deeper penetration. Organic solvents, such as benzene, toluene, and xylene (BTX), have been detected in humans following skin exposure. In this study, novel barrier cream formulations (EVBTM) engineered with either montmorillonite (CM and SM) or chlorophyll-amended montmorillonite (CMCH and SMCH) clays were tested for their binding efficacy for BTX mixtures in water. The physicochemical properties of all sorbents and barrier creams were characterized and were shown to be suitable for topical application. In vitro adsorption results indicated that EVB-SMCH was the most effective and favorable barrier for BTX, as supported by the high binding percentage (29–59% at 0.05 g and 0.1 g), stable binding at equilibrium, low desorption rates, and high binding affinity. Pseudo-second-order and the Freundlich models best fit the adsorption kinetics and isotherms, and the adsorption was an exothermic reaction. Ecotoxicological models using L. minor and H. vulgaris that were submersed in aqueous culture media showed that the inclusion of 0.05% and 0.2% EVB-SMCH reduced BTX concentration. This result was further supported by the significant and dose-dependent increase in multiple growth endpoints, including plant frond number, surface area, chlorophyll content, growth rate, inhibition rate, and hydra morphology. The in vitro adsorption results and in vivo plant and animal models indicated that green-engineered EVB-SMCH can be used as an effective barrier to bind BTX mixtures and interrupt their diffusion and dermal contact. Full article
(This article belongs to the Special Issue Applications of Porous Materials in Adsorption)
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24 pages, 6367 KiB  
Review
Removal of Azo Dyes from Wastewater through Heterogeneous Photocatalysis and Supercritical Water Oxidation
by Vincenzo Vaiano and Iolanda De Marco
Separations 2023, 10(4), 230; https://doi.org/10.3390/separations10040230 - 27 Mar 2023
Cited by 22 | Viewed by 5404
Abstract
Azo dyes are synthetic organic dyes used in the textile, leather, and paper industries. They pose environmental problems due to their toxic and persistent nature. The toxicity is due to the presence of azo groups in the dye molecule that can break down [...] Read more.
Azo dyes are synthetic organic dyes used in the textile, leather, and paper industries. They pose environmental problems due to their toxic and persistent nature. The toxicity is due to the presence of azo groups in the dye molecule that can break down into aromatic amines, which are highly toxic to aquatic organisms and humans. Various treatment methods have been developed to remove azo dyes from wastewater. Conventional wastewater treatments have some drawbacks, such as high operating costs, long processing times, generation of sludge, and the formation of toxic by-products. For these reasons, a valid alternative is constituted by advanced oxidation processes. Good results have been obtained using heterogeneous photocatalysis and supercritical water oxidation. In the former method, a photocatalyst is in contact with wastewater, a suitable light activates the catalyst, and generated reactive oxygen species that react with pollutants through oxidative reactions to their complete mineralization; the latter involves pressurizing and heating wastewater to supercritical conditions in a reactor vessel, adding an oxidizing agent to the supercritical water, and allowing the mixture to react. In this review paper, works in the literature that deal with processing wastewater containing azo dyes through photocatalysts immobilized on macroscopic supports (structured photocatalysts) and the supercritical water oxidation technique have been critically analyzed. In particular, advancement in the formulation of structured photocatalysts for the degradation of azo dyes has been shown, underlying different important features, such as the type of support for the photoactive phase, reactor configuration, and photocatalytic efficiency in terms of dye degradation and photocatalyst stability. In the case of supercritical water oxidation, the main results regarding COD and TOC removal from wastewater containing azo dyes have been reported, taking into account the reactor type, operating pressure, and temperature, as well as the reaction time. Full article
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15 pages, 1865 KiB  
Article
Development and Validation of a Confirmatory Method for the Determination of 12 Coccidiostat Residues in Eggs and Muscle by Means of Liquid Chromatography Coupled to Hybrid High Resolution Mass Spectrometry
by Federica Castellani, Matteo Ricci, Maria Novella Colagrande, Giampiero Scortichini and Giorgio Saluti
Separations 2023, 10(3), 202; https://doi.org/10.3390/separations10030202 - 14 Mar 2023
Cited by 5 | Viewed by 2027
Abstract
A confirmatory, highly selective multi-residue method based on liquid chromatography coupled to hybrid high resolution mass spectrometry (LC-Q-Orbitrap) was developed and validated for the determination of 12 regulated coccidiostats in eggs and muscle. Particularly, ionophore antibiotics (lasalocid, maduramicin, monensin, narasin, salinomycin and semduramicin) [...] Read more.
A confirmatory, highly selective multi-residue method based on liquid chromatography coupled to hybrid high resolution mass spectrometry (LC-Q-Orbitrap) was developed and validated for the determination of 12 regulated coccidiostats in eggs and muscle. Particularly, ionophore antibiotics (lasalocid, maduramicin, monensin, narasin, salinomycin and semduramicin) and synthetic coccidiostats (diclazuril, halofuginone, nicarbazin as 4,4′-dinitrocarbanilide fraction, robenidine and toltrazuril as toltrazuril-sulphone) were included in the method. The sample preparation consisted in the extraction of the analytes from the matrix with acetonitrile, followed by a clean-up step with Oasis® PRiME HLB SPE and a defatting procedure with n-hexane. Validation was successfully performed according to Commission Implementing Regulation (EU) 2021/808, starting from 1 µg kg−1. The procedure was verified through the analysis of a certified reference material (CRM) and the occurrence of the residues was assessed in the context of the Italian National Residue Control Plan (NRCP). Full article
(This article belongs to the Special Issue Novel Applications of Separation Technology)
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32 pages, 3193 KiB  
Review
Application of Hydrogen-Bonded Organic Frameworks in Environmental Remediation: Recent Advances and Future Trends
by Yu Zhang, Mengfei Tian, Zahid Majeed, Yuxin Xie, Kaili Zheng, Zidan Luo, Chunying Li and Chunjian Zhao
Separations 2023, 10(3), 196; https://doi.org/10.3390/separations10030196 - 13 Mar 2023
Cited by 7 | Viewed by 3647
Abstract
The hydrogen-bonded organic frameworks (HOFs) are a class of porous materials with crystalline frame structures, which are self-assembled from organic structures by hydrogen bonding in non-covalent bonds π-π packing and van der Waals force interaction. HOFs are widely used in environmental remediation due [...] Read more.
The hydrogen-bonded organic frameworks (HOFs) are a class of porous materials with crystalline frame structures, which are self-assembled from organic structures by hydrogen bonding in non-covalent bonds π-π packing and van der Waals force interaction. HOFs are widely used in environmental remediation due to their high specific surface area, ordered pore structure, pore modifiability, and post-synthesis adjustability of various physical and chemical forms. This work summarizes some rules for constructing stable HOFs and the synthesis of HOF-based materials (synthesis of HOFs, metallized HOFs, and HOF-derived materials). In addition, the applications of HOF-based materials in the field of environmental remediation are introduced, including adsorption and separation (NH3, CO2/CH4 and CO2/N2, C2H2/C2He and CeH6, C2H2/CO2, Xe/Kr, etc.), heavy metal and radioactive metal adsorption, organic dye and pesticide adsorption, energy conversion (producing H2 and CO2 reduced to CO), organic dye degradation and pollutant sensing (metal ion, aniline, antibiotic, explosive steam, etc.). Finally, the current challenges and further studies of HOFs (such as functional modification, molecular simulation, application extension as remediation of contaminated soil, and cost assessment) are discussed. It is hoped that this work will help develop widespread applications for HOFs in removing a variety of pollutants from the environment. Full article
(This article belongs to the Special Issue Applications of Porous Materials in Adsorption)
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18 pages, 4876 KiB  
Article
Deep Eutectic Solvent-Based Microwave-Assisted Extraction for the Extraction of Seven Main Flavonoids from Ribes mandshuricum (Maxim.) Kom. Leaves
by Wei Wang, Si-Qiu Xiao, Ling-Yu Li and Qing-Yan Gai
Separations 2023, 10(3), 191; https://doi.org/10.3390/separations10030191 - 10 Mar 2023
Cited by 5 | Viewed by 2442
Abstract
Flavonoids exhibit many biological properties, so it is very important to find an efficient and green method to extract them from plant materials. In this paper, DES-MAE (deep eutectic solvent-based microwave-assisted extraction) technique was developed to extract the seven major active flavonoids from [...] Read more.
Flavonoids exhibit many biological properties, so it is very important to find an efficient and green method to extract them from plant materials. In this paper, DES-MAE (deep eutectic solvent-based microwave-assisted extraction) technique was developed to extract the seven major active flavonoids from Ribes mandshuricum leaves, namely, trifolin, isoquercetin, rutin, astragalin, quercetin, hyperoside, and kaempferol. After the completion of the extraction process, macroporous adsorption resin was used for the purification of seven flavonoids. The BBD (Box–Behnken design) method combined with RSM (response surface methodology) was applied to acquire the optimal operating conditions of DES-MAE. The optimal parameters were: temperature: 54 °C, time: 10 min, extraction solvent: choline chloride/lactic acid with a 1:2 mass ratio, water content: 25%, and liquid/solid ratio: 27 mL/g. The yields of the seven target flavonoids were 4.78, 2.57, 1.25, 1.15, 0.34, 0.32, and 0.093 mg/g DW (dry weight), respectively. The direct purification of trifolin, isoquercetin, rutin, astragalin, quercetin, hyperoside, and kaempferol in DES-MAE solution was achieved by using macroporous resin X-5. The recoveries were 87.02%, 81.37%, 79.64%, 87.13%, 97.36%, 88.08%, and 99.39%, respectively. The results showed that DES-MAE followed by MRCC (macroporous resin column chromatography) represents a promising approach to extracting and separating active components from plants. Full article
(This article belongs to the Special Issue Novel Approach for Natural Product Separation from Plants)
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15 pages, 7415 KiB  
Review
Steric Exclusion Chromatography for Purification of Biomolecules—A Review
by Jennifer J. Labisch, G. Philip Wiese and Karl Pflanz
Separations 2023, 10(3), 183; https://doi.org/10.3390/separations10030183 - 8 Mar 2023
Cited by 2 | Viewed by 2891
Abstract
Steric exclusion chromatography (SXC) is a purification method that is based on steric exclusion effects from the surface of the target and a hydrophilic stationary phase after the addition of polyethylene glycol (PEG), which leads to an association of the target with the [...] Read more.
Steric exclusion chromatography (SXC) is a purification method that is based on steric exclusion effects from the surface of the target and a hydrophilic stationary phase after the addition of polyethylene glycol (PEG), which leads to an association of the target with the stationary phase without direct binding, such as covalent, electrostatic, and hydrophilic/hydrophobic interactions. The gentle nature of the method has led to an increased focus on sensitive targets such as enveloped viruses with potential for other sensitive entities, e.g., extracellular vesicles and virus-like particles. SXC is related to PEG-mediated protein precipitation, but investigation of further process parameters was crucial to gain a better understanding of the SXC method. After explaining mechanistic fundamentals and their discovery, this review summarizes the findings on SXC from its first reference 11 years ago until today. Different applications of SXC are presented, demonstrating that the method can be used for a wide variety of targets and achieves high recovery rates and impurity removal. Further, critical process parameters for successful process implementation are discussed, including technical requirements, buffer composition, and scalability. Full article
(This article belongs to the Special Issue Advances in Separation Engineering)
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17 pages, 2117 KiB  
Article
Experimental Design and Multiple Response Optimization for the Extraction and Quantitation of Thirty-Four Priority Organic Micropollutants in Tomatoes through the QuEChERS Approach
by Luca Rivoira, Massimo Del Bubba, Giasmin Cecconi, Michele Castiglioni, Valentina Testa, Mattia Isola and Maria Concetta Bruzzoniti
Separations 2023, 10(3), 174; https://doi.org/10.3390/separations10030174 - 6 Mar 2023
Cited by 2 | Viewed by 1888
Abstract
The chemical contamination in fruit and vegetables represents a challenging analytical issue, with tomatoes deserving to be investigated as they are fundamental components of the Mediterranean diet. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs contamination is of serious concern, due to [...] Read more.
The chemical contamination in fruit and vegetables represents a challenging analytical issue, with tomatoes deserving to be investigated as they are fundamental components of the Mediterranean diet. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs contamination is of serious concern, due to particulate deposition and to uptake from contaminated soils and water. However, time-consuming, non-simultaneous and/or non-eco-friendly extraction procedures are typically used to investigate organic contamination in tomatoes, with nitro-PAHs that have not yet been studied. Based on these premises, this work reports the development of a QuEChERS-based approach, coupled with gas chromatography/mass spectrometry, for the simultaneous determination of 16 PAHs, 14 PCBs and 4 nitro-PAHs in three tomato cultivars. The effect of dichloromethane, cyclohexane and acetone, as well as of four clean-up phases were studied through the advanced combination of full factorial experimental design and multiple response optimization approaches. The final protocol, based on cyclohexane extraction followed by a double purification step with primary secondary amine and octadecyl silica and a sulfuric acid oxidation, led to 60–120% recoveries (RSD% < 15%). Good repeatability (inter-day precision <15%) and negligible matrix effect (<16%) were confirmed and the protocol was applied to the analysis of real tomato samples purchased in a local market. Full article
(This article belongs to the Section Environmental Separations)
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