Journal Description
Separations
Separations
- formerly Chromatography - is an international, peer-reviewed, open access journal on separation and purification science and technology in all areas of chemical, biological, physical science, and separation performance published monthly online by MDPI. The Central European Group of Separation Sciences (CEGSS) is affiliated with Separations and their members receive discounts on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), CAPlus / SciFinder, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 13.6 days after submission; acceptance to publication is undertaken in 2.9 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journal: Purification.
Impact Factor:
2.6 (2022);
5-Year Impact Factor:
2.7 (2022)
Latest Articles
Simultaneous Quantification of Twelve Compounds from Bamboo/Wood Vinegar by Gas Chromatography-Mass Spectrometry
Separations 2024, 11(6), 168; https://doi.org/10.3390/separations11060168 - 28 May 2024
Abstract
Bamboo vinegar is a liquid biomass with a huge yield and complex chemical composition. At present, the relative quantification of bamboo vinegar has been investigated in most studies. To analyze twelve compounds from bamboo vinegar simultaneously, gas chromatography-mass spectrometry and an external standard
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Bamboo vinegar is a liquid biomass with a huge yield and complex chemical composition. At present, the relative quantification of bamboo vinegar has been investigated in most studies. To analyze twelve compounds from bamboo vinegar simultaneously, gas chromatography-mass spectrometry and an external standard method were used to develop an analytical method. In this method, chromatographic separations of all compounds were above 1.5. The linear range was between 0.100 and 10.000 mg/L, and the coefficient of determination (R2) was between 0.9981 and 0.9997, indicating a good linear relationship. The limit of detection (LOD) was between 0.004 and 0.780 mg/L; the limit of quantitation (LOQ) was between 0.016 and 3.120 mg/L; the relative standard deviations (RSDs) of instrument precision and method stability were less than 8%; the recovery rate was between 89.25% and 113.77%, and its RSD was between 0.44% and 5.70%. Using this method, fourteen bamboo vinegars and six wood vinegars were analyzed, and it was found that the content of propionic acid, phenol, and 2-methoxyphenol was higher in most samples. In addition, the differences in physicochemical properties between distilled bamboo vinegar and its original solution after atmospheric distillation were investigated.
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(This article belongs to the Special Issue Comprehensive Separations of Complex Mixtures by Gas Chromatography/Mass Spectrometry (Volume II))
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Open AccessArticle
Early Identification of Olive Oil Defects throughout Shelf Life
by
Flávia Freitas, Maria João Cabrita and Marco Gomes da Silva
Separations 2024, 11(6), 167; https://doi.org/10.3390/separations11060167 - 27 May 2024
Abstract
The unique aroma and flavor of extra virgin olive oil (EVOO) are generally associated with its volatile composition, which includes a variety of components responsible for positive attributes as well as sensory defects which result from chemical oxidation processes and the action of
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The unique aroma and flavor of extra virgin olive oil (EVOO) are generally associated with its volatile composition, which includes a variety of components responsible for positive attributes as well as sensory defects which result from chemical oxidation processes and the action of exogenous enzymes. In this study, a robust analytical method, headspace solid-phase microextraction combined with gas chromatography–mass spectrometry (HS-SPME-GC/MS), was developed to tentatively identify volatile organic compounds (VOCs) as markers of positive and negative attributes, correlating them with relative percentages to estimate the risk of disqualification during the shelf life of EVOO. Significant differences (p < 0.05) were identified in the levels of VOCs over time, mainly those derived from the lipoxygenase (LOX) pathway. Principal component analysis (PCA) was applied to process the experimental data. The ratio of E-2-hexenal to acetic acid allowed for the prediction of the disqualification of monovarietal EVOO by the sensory panel.
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(This article belongs to the Section Analysis of Food and Beverages)
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Open AccessReview
Current Trends and Technological Advancements in the Study of Honey Bee-Derived Peptides with an Emphasis on State-of-the-Art Approaches: A Review
by
Wissam K. Al-Rubaie, Dhia F. Al-Fekaiki, Alaa Kareem Niamah, Deepak Kumar Verma, Smita Singh and Ami R. Patel
Separations 2024, 11(6), 166; https://doi.org/10.3390/separations11060166 - 27 May 2024
Abstract
Honey is a natural product that is used by a large number of people because of its distinctive compositional constituents, which have a considerable impact on its market value. The distinctive combination of amino acids and sugars found in honey’s composition, along with
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Honey is a natural product that is used by a large number of people because of its distinctive compositional constituents, which have a considerable impact on its market value. The distinctive combination of amino acids and sugars found in honey’s composition, along with its peptide content, could potentially provide several benefits to human health. During the past few years, cutting-edge techniques have been developed and used for the purpose of investigating, identifying, and characterizing peptides that are produced from honey bees. Therefore, the purpose of this review is to examine current trends and technological advancements in the study of honey bee-derived peptides, focusing on innovative and cutting-edge methods. Furthermore, this review explores various attributes of honey and its components, including the honey bee-derived peptide defensin-1. In addition, this review investigates various methods for separating and purifying peptides, as well as the factors that affect these methods. Additionally, defensin-1, a peptide produced by honey bees, is discussed along with its antioxidant and antimicrobial capabilities. In addition, this review focuses on cutting-edge and innovative omic methods used to study honey bee peptides, as well as the significance of artificial intelligence tools in their investigation. Consequently, the review paper delves into various significant obstacles faced by researchers and scientists studying honey bee peptides, while also offering an extensive range of fascinating opportunities and possibilities for future research for those interested in groundbreaking discoveries in this area.
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(This article belongs to the Section Analysis of Food and Beverages)
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Open AccessArticle
Accessing the Medicinal Potential of Mallotus philippensis: Comprehensive Exploration of Antioxidant and Antibacterial Properties through Phytochemical Analysis and Extraction Techniques
by
Ahmad Ali, Hangping Chen, He Xu, Shuo Wang and Shun Yao
Separations 2024, 11(6), 165; https://doi.org/10.3390/separations11060165 - 27 May 2024
Abstract
Plants serve as reservoirs of bioactive compounds endowed by nature, rendering them promising subjects for investigating chemical diversity. Despite their potential, much remains untapped, whether in standardized extracts or isolated pure compounds. This unexplored terrain has paved the way for significant discoveries in
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Plants serve as reservoirs of bioactive compounds endowed by nature, rendering them promising subjects for investigating chemical diversity. Despite their potential, much remains untapped, whether in standardized extracts or isolated pure compounds. This unexplored terrain has paved the way for significant discoveries in pharmaceuticals. Notably, research has delved into the medicinal properties of Mallotus philippensis, a prominent plant in South Asia. Employing meticulous extraction techniques such as maceration, the fruit of this plant underwent initial antimicrobial screening, revealing encouraging results. Subsequent fractionation of the plant’s extracts via liquid–liquid extractions, utilizing dichloromethane and absolute ethanol, facilitated further analysis. Evaluating these fractions for antibacterial activity demonstrated efficacy against various pathogenic microorganisms, particularly Pseudomonas aeruginosa and Escherichia coli, notably by the ethanolic and dichloromethane extracts. Furthermore, a comprehensive phytochemical analysis unveiled the presence of alkaloids, flavonoids, saponins, glycosides, phenols, and tannins. An assessment of the extracts’ antioxidant potential via the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay showcased significant activity, with a radical scavenging rate of 97%. This underscores the significance of utilizing fruit remnants, which are often rich in valuable chemical constituents yet commonly discarded, thereby adding value to both the species and the environment. Further investigation focused on the composition of Mallotus philippensis fruit, encompassing volatile and non-volatile metabolites through HPLC-MS analysis. Additionally, this study introduced the application of ionic liquid-loaded polysulfone microcapsules to enrich target constituents from crude extracts. An exploration of the key separation conditions, results, and recycling performance of these microcapsules provided insights for future research endeavors. Overall, this comprehensive study of Mallotus philippensis fruit extracts establishes a foundation for the ongoing exploration and development of this medicinal plant.
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(This article belongs to the Section Analysis of Natural Products and Pharmaceuticals)
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Open AccessArticle
Carwash Oily Wastewater Separated by Ultrafiltration
by
Piotr Woźniak and Marek Gryta
Separations 2024, 11(6), 164; https://doi.org/10.3390/separations11060164 - 25 May 2024
Abstract
In the present study, oily wastewater generated during car washing was separated using ultrafiltration (UF). Wastewater was collected from the settling tank of two manual car washes. In addition to pollutants removed from cars, such wastewater contains surfactants, the impact of which on
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In the present study, oily wastewater generated during car washing was separated using ultrafiltration (UF). Wastewater was collected from the settling tank of two manual car washes. In addition to pollutants removed from cars, such wastewater contains surfactants, the impact of which on the process of ultrafiltration has been analyzed. For this purpose, the application of commercial UF polyethersulfone (PES) membranes (10 and 100 kDa) and polyvinylidene fluoride (PVDF) tubular membranes (100 kDa) was comprehensively examined. Almost 100% removal of oil contaminants was achieved; however, intensive fouling was noticed. The membrane morphology and deposit composition were studied using a scanning electron microscope coupled with energy dispersion spectrometry. The fouling phenomenon was reduced by washing the membranes with an alkaline cleaning agent (pH = 11.5), which is used in car washes to remove insects. The filtration/membrane washing cycle was repeated many times to achieve stable operation of the membrane modules. The UF process was carried out for 120–140 h, and the separation efficiency was analyzed based on the rejection of dextrans, COD, BOD, total N and P, turbidity, and anionic surfactants. It has been found that cyclic repeated washing did not deteriorate the membrane’s performance, and a permeate with a turbidity of 0.12–0.35 NTU was obtained. Thus, cleaning agents used for washing cars can also be used for membrane cleaning.
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(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)
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Open AccessArticle
Accumulation of Particles in an Annular Centrifugal Contactor Cascade and the Effect upon the Extraction of Nitric Acid
by
Alastair Baker, Alex Fells, Natalia Domenech-Garcia, Chris J. Maher and Bruce C. Hanson
Separations 2024, 11(6), 163; https://doi.org/10.3390/separations11060163 - 23 May 2024
Abstract
Centrifugal contactors (CCs) are a technology candidate for the development of advanced reprocessing flowsheets. While they offer many advantages, such as process intensification, there are still uncertainties regarding their industrial deployment. The presence of particles in the process streams in particular may present
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Centrifugal contactors (CCs) are a technology candidate for the development of advanced reprocessing flowsheets. While they offer many advantages, such as process intensification, there are still uncertainties regarding their industrial deployment. The presence of particles in the process streams in particular may present a challenge to both performance and operability. Preliminary studies have been undertaken to evaluate the accumulation of particles in the contactors and the effect upon the extraction behaviour of nitric acid. Aluminium oxide (Al2O3) particles were suspended in the aqueous feed solution during the operation of a three-stage, 40 mm diameter CC cascade. The presence of insoluble solid particles in the aqueous feed, up to 7 g/L, were not observed to affect phase separation and entrainment under the experimental conditions investigated. The particles were centrifuged out of solution and accumulated as a thin cake/bed in the rotors of each stage. This work also illustrates that particles do entrain through the cascade. The predominant effect on the rate of accumulation was particle concentration in the aqueous feed solution, and increasing solids loading was observed to have an impact upon the extraction of nitric acid across the cascade.
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(This article belongs to the Section Separation Engineering)
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Open AccessArticle
Hyphenation of Thermodesorption into GC × GC-TOFMS for Odorous Molecule Detection in Car Materials: Column Sets and Adaptation of Second Column Dimensions to TD Pressure Constraints
by
Romain Klein, José Dugay, Jérôme Vial, Didier Thiébaut, Guy Colombet, Donatien Barreteau and Guillaume Gruntz
Separations 2024, 11(6), 162; https://doi.org/10.3390/separations11060162 - 23 May 2024
Abstract
Vehicle interior air quality is an issue of growing interest among car manufacturers and customers. GC-MS is the benchmark method for the analysis of indoor air or material emissions. It is suitable for the quantification of target pollutants and the most abundant compounds.
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Vehicle interior air quality is an issue of growing interest among car manufacturers and customers. GC-MS is the benchmark method for the analysis of indoor air or material emissions. It is suitable for the quantification of target pollutants and the most abundant compounds. It fails, however, to uncover the true molecular complexity of these samples. In the present study, we describe the development of a TD-GC × GC-TOFMS method designed to detect polar and potentially odorous molecules in car material emissions. Attention is paid to the hyphenation of the thermodesorber and the gas chromatograph, both at software and hardware levels, and the constraints due to pressure limitations on the thermodesorber (evaluated at 414 kPa/60 psi at the end of the temperature ramp and at 138 kPa/20 psi at rest). A compromise was made for the 2D column length and diameter to balance separation and pressure (50 × 0.18 × 0.18 cm × mm × µm + 60 cm transfer line selected). On various materials, we were able to observe several hundreds of polar molecules, among them were between 75 and 150 odorants per material. This work lays the foundation for the widespread screening of potential odorants in car material emissions.
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(This article belongs to the Collection Feature Paper Collection in Section Chromatographic Separations)
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Two-Dimensional Thin-Layer Chromatography as an Accessible, Low-Cost Tool for Lipid-Class Profile Screening
by
Zipora Tietel
Separations 2024, 11(6), 161; https://doi.org/10.3390/separations11060161 - 23 May 2024
Abstract
The interest in lipid composition profiling is significantly increasing as research reveals the immense importance of lipids in medicine, plant science, food and agriculture. However, lipidomic analysis requires high-end specialty equipment. We used two-dimensional thin-layer chromatography (2D-TLC) as a readily available, low-cost tool
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The interest in lipid composition profiling is significantly increasing as research reveals the immense importance of lipids in medicine, plant science, food and agriculture. However, lipidomic analysis requires high-end specialty equipment. We used two-dimensional thin-layer chromatography (2D-TLC) as a readily available, low-cost tool for basic lipidomic profiling of lipid classes in algal samples in the models Chlamydomonas reinhardtii, Auxenochlorella protothecoides, and Euglena gracilis, validating lipid class identification using an LC-MS/MS analysis. Algal lipid extracts were separated on a 2D-TLC plate, and TLC analysis was followed by scraping individual TLC spots off the plate, and a subsequent liquid chromatography separation and tandem mass spectrometry (LC-MS/MS) analysis. For comparison, crude lipid extracts were also injected directly to the LC-MS/MS system. Lipid class annotation was achieved by a combination of accurate mass, retention time information, neutral loss and fragment ion analysis by MS2Analyzer, and by matching spectra to LipidBlast MS/MS library. Overall, we were able to identify 15 lipid classes, and to adequately profile the lipid classes in all three organisms. This TLC method is thus suggested as an accessible tool for lipid class profiling of algal, plant, and food lipids, alike, when a rapid and simple analysis is required, e.g., for screening purposes.
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(This article belongs to the Special Issue Chromatography for the Separation and Detection of Metabolites)
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Open AccessArticle
Evaluation of CO2/H2O Co-Adsorption Models for the Anion Exchange Resin Lewatit VPOC 1065 under Direct Air Capture Conditions Using a Novel Lab Setup
by
Florian M. Chimani, Aditya Anil Bhandari, Andreas Wallmüller, Gerhard Schöny, Stefan Müller and Josef Fuchs
Separations 2024, 11(6), 160; https://doi.org/10.3390/separations11060160 - 22 May 2024
Abstract
This study aimed to develop a laboratory-scale direct air capture unit for evaluating and comparing amine-based adsorbents under temperature vacuum swing adsorption conditions. The experimental campaign conducted with the direct air capture unit allowed for the determination of equilibrium loading, CO2 uptake
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This study aimed to develop a laboratory-scale direct air capture unit for evaluating and comparing amine-based adsorbents under temperature vacuum swing adsorption conditions. The experimental campaign conducted with the direct air capture unit allowed for the determination of equilibrium loading, CO2 uptake capacity, and other main performance parameters of the investigated adsorbent Lewatit VP OC 1065®. The investigations also helped to understand the co-adsorption of CO2 and H2O on the tested material, which is crucial for improving temperature vacuum swing adsorption processes. This was achieved by obtaining pure component isotherms for CO2 and H2O and using three different co-adsorption isotherm models from the literature. It was found that the weighted average dual-site Toth model emerged as the most accurate and reliable model for simulating this co-adsorption behaviour. Its predictions closely align with the experimental data, particularly in capturing the adsorption equilibrium at various temperatures. It was also observed that this lab-scale unit offers advantages over thermogravimetric analysis when conducting adsorption experiments on the chosen amine. The final aim of this study is to provide a pathway to develop devices for testing and developing efficient and cost-effective adsorbents for direct air capture.
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(This article belongs to the Topic Carbon Capture Science & Technology (CCST))
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Effect of a Chitosan-Based Packaging Material on the Domestic Storage of “Ready-to-Cook” Meat Products: Evaluation of Biogenic Amines Production, Phthalates Migration, and In Vitro Antimicrobic Activity’s Impact on Aspergillus Niger
by
Antonella Maria Aresta, Nicoletta De Vietro, Giovanna Mancini and Carlo Zambonin
Separations 2024, 11(6), 159; https://doi.org/10.3390/separations11060159 - 21 May 2024
Abstract
The consumption of “ready-to-cook” foods has been experiencing rapid expansion due to modern lifestyles, and they are often sold in economical multipacks. These foods necessitate packaging that maintains their quality for extended periods of time during home storage once the original packaging is
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The consumption of “ready-to-cook” foods has been experiencing rapid expansion due to modern lifestyles, and they are often sold in economical multipacks. These foods necessitate packaging that maintains their quality for extended periods of time during home storage once the original packaging is opened. This study evaluates a chitosan-based film derived from low- and high-molecular-weight (MW) chitosan in acetic acid without synthetic additives as an alternative packaging material for “ready-to-cook” beef burgers. The burgers were stored at 8 °C after being removed from their sales packaging. A commercial polyethylene (PE) film designed for food use, devoid of polyvinylchloride (PVC) and additives, served as the reference material. The production of six biogenic amines (BAs), indicative of putrefactive processes, was monitored. Additionally, the release of four phthalates (PAEs), unintentionally present in the packaging films, was assessed using solid-phase microextraction coupled with gas chromatography/mass spectrometry (SPME-GC/MS). Microbiological tests were conducted to investigate the antimicrobial efficacy of the packaging against Aspergillus Niger NRR3112. The results showed that the chitosan-based films, particularly those with low MW (LMW), exhibited superior meat preservation compared to the PE films. Furthermore, they released PAEs below legal limits and demonstrated the complete inhibition of fungal growth. These findings highlight the potential of chitosan-based packaging as a viable and effective option for extending the shelf-life and maintaining the quality of “ready-to-cook” meat products during domestic storage.
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(This article belongs to the Section Analysis of Food and Beverages)
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Open AccessArticle
Polyphenols from Sage Leaves (Salvia officinalis L.): Environmentally Friendly Extraction under High Hydrostatic Pressure and Application as a Corrosion Inhibitor for Tinplate
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Maja Dent, Regina Fuchs-Godec, Sandra Pedisić, Dorotea Grbin, Verica Dragović-Uzelac, Damir Ježek and Tomislav Bosiljkov
Separations 2024, 11(5), 158; https://doi.org/10.3390/separations11050158 - 17 May 2024
Abstract
Due to the diversity of organic molecular structures present in sage extract, sage extract is a promising potential source of a cheap and effective biodegradable green corrosion inhibitor for tinplate in 3% NaCl solution, which was evaluated in this study. HHP proved to
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Due to the diversity of organic molecular structures present in sage extract, sage extract is a promising potential source of a cheap and effective biodegradable green corrosion inhibitor for tinplate in 3% NaCl solution, which was evaluated in this study. HHP proved to be a new and emerging technology for the useful extraction of polyphenols from sage as a functional ingredient from natural sources. Analysis of variance among all tested independent factors (ethanol concentration, HHP parameters and temperature) revealed significant differences (p < 0.05) in total polyphenol content as well as for rosmarinic acid as the major phenolic compound in sage extract, while extraction time had no effect (p ˃ 0.05). The optimum HHP conditions (600 MPa, 30% ethanol, 60 °C and 5 min) gave a maximum extraction yield of total polyphenols of 3811.84 mg/100 g. Sage-leaf extracts were found to be a mixture of phenolic acids, namely rosmarinic and salvianolic acid K, epicatechin and luteolin-7-O-glucuronide glycoside. The corrosion results show that the sage extract at a concentration of 0.6 g/L in 3% NaCl is an effective corrosion inhibitor (93%), forming a passivation layer of sage extract consisting of organic compounds such as polyphenols on the surface of tinplate.
Full article
(This article belongs to the Special Issue Bioactive Compounds from Natural Sources: Extraction, Characterization, Evaluation and Application)
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Open AccessArticle
Characterization and Quantitation of Anthocyanins of the Pigmented Tea Cultivar TRI 2043 (Camellia sinensis L.) from Sri Lanka
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Philipp Hopfstock, Pitumpe Appuhamilage Nimal Punyasiri, Mats Kiene, Jeevan Dananjava Kottawa-Arachchi, Recep Gök and Peter Winterhalter
Separations 2024, 11(5), 157; https://doi.org/10.3390/separations11050157 - 16 May 2024
Abstract
Tea leaves are rich in diverse bioactive compounds. The tea accession TRI 2043 is unique due to its pigmented leaves caused by anthocyanins, clonal origin, resistance to blister blight disease, and high pubescence density. Because of its peculiarity, TRI 2043 is used to
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Tea leaves are rich in diverse bioactive compounds. The tea accession TRI 2043 is unique due to its pigmented leaves caused by anthocyanins, clonal origin, resistance to blister blight disease, and high pubescence density. Because of its peculiarity, TRI 2043 is used to produce high-quality silver tip tea, a premium type of tea that commands high prices. This study was carried out to clarify and elucidate the types of anthocyanins in this particular accession. Four different anthocyanin species were identified and quantitated as cyanidin-3-O-β-d-galactoside and delphinidin-3-O-β-d-galactoside equivalents for leaf blades and stems of the cultivar TRI 2043. The characterization was performed by comparison with commercially available reference substances and further confirmed using ion mobility high-resolution time-of-flight-mass spectrometry (IMS-HRTOF-MS). Quantitation was carried out using ultra-high-performance liquid chromatography ultraviolet–visible detection (UHPLC-UV-vis) with cyanidin-3-O-β-d-glucoside as an internal standard. E- and Z-geometric isomers of 6-p-coumaroyl derivates of delphinidin and cyanidin-3-O-β-d-galactopyranosides were observed, and collision cross section (CCS) values were determined for all four different anthocyanidin species. The content of anthocyanins in leaf blades of cultivar TRI 2043 was 856.32 ± 41.56 µg/g dry weight, with cyanidin being the more abundant anthocyanin (69.8%). Conversely, the stem material contained an anthocyanin amount of 459.5 ± 44.7 µg/g dry weight, with a higher content of delphinidin (69.6%). In summary, an enrichment strategy using analytical membrane chromatography was established to fully elucidate and quantify the anthocyanin profile of plant samples such as the special tea variety TRI 2043.
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(This article belongs to the Special Issue Bioactive Compounds in Foods: Separation, Extraction and Application)
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Open AccessArticle
Efficient Quality Control of Peptide Pools by UHPLC and Simultaneous UV and HRMS Detection
by
Gaby Bosc-Bierne, Shireen Ewald, Oliver J. Kreuzer and Michael G. Weller
Separations 2024, 11(5), 156; https://doi.org/10.3390/separations11050156 - 16 May 2024
Abstract
Peptide pools consist of short amino acid sequences and have proven to be versatile tools in various research areas in immunology and clinical applications. They are commercially available in many different compositions and variants. However, unlike other reagents that consist of only one
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Peptide pools consist of short amino acid sequences and have proven to be versatile tools in various research areas in immunology and clinical applications. They are commercially available in many different compositions and variants. However, unlike other reagents that consist of only one or a few compounds, peptide pools are highly complex products which makes their quality control a major challenge. Quantitative peptide analysis usually requires sophisticated methods, in most cases isotope-labeled standards and reference materials. Usually, this would be prohibitively laborious and expensive. Therefore, an approach is needed to provide a practical and feasible method for quality control of peptide pools. With insufficient quality control, the use of such products could lead to incorrect experimental results, worsening the well-known reproducibility crisis in the biomedical sciences. Here we propose the use of ultra-high performance liquid chromatography (UHPLC) with two detectors, a standard UV detector at 214 nm for quantitative analysis and a high-resolution mass spectrometer (HRMS) for identity confirmation. To be cost-efficient and fast, quantification and identification are performed in one chromatographic run. An optimized protocol is shown, and different peak integration methods are compared and discussed. This work was performed using a peptide pool known as CEF advanced, which consists of 32 peptides derived from cytomegalovirus (CMV), Epstein–Barr virus (EBV) and influenza virus, ranging from 8 to 12 amino acids in length.
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(This article belongs to the Special Issue Peptide Synthesis, Separation and Purification)
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Open AccessCommunication
Coordination Ion Spray for Analysis of the Growth Hormones Releasing Peptides in Urine—An Application Study
by
Azamat Temerdashev, Elina Gashimova, Alice Azaryan, Yu-Qi Feng and Sanka N. Atapattu
Separations 2024, 11(5), 155; https://doi.org/10.3390/separations11050155 - 16 May 2024
Abstract
In this article, a comparison of ionization techniques is provided and discussed. Conventional liquid chromatography with an electrospray ionization source shows higher robustness and repeatability in comparison with liquid chromatography coupled with a coordination ion spray (CIS-MS) source using silver nitrate as the
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In this article, a comparison of ionization techniques is provided and discussed. Conventional liquid chromatography with an electrospray ionization source shows higher robustness and repeatability in comparison with liquid chromatography coupled with a coordination ion spray (CIS-MS) source using silver nitrate as the dopant. However, the higher sensitivity and possibility to collect more data in untargeted applications mean CIS-MS is emerging as an instrument used in specific applications. During this research, the limit of detection (LOD) for GHRP-2 and GHRP-6 was established at 0.2 ng/mL, and the lower limit of quantification (LLOQ) was 0.5 ng/mL for CIS-MS. For conventional ESI-MS combined with solid-phase extraction on weak cation exchange columns, the limit of detection was found to be 1 ng/mL, and the lower limit of quantification was 2 ng/mL.
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(This article belongs to the Topic Application of Liquid Chromatography-Mass Spectrometry and Related Techniques)
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Open AccessArticle
Improving the Current European Pharmacopoeia Enantio-Selective HPLC Method for the Determination of Enantiomeric Purity in Atorvastatin Calcium Salt Drug Substance
by
Francesca Romana Mammone, Daniele Sadutto, Giulia D’Ettorre, Antonina Mosca and Roberto Cirilli
Separations 2024, 11(5), 154; https://doi.org/10.3390/separations11050154 - 16 May 2024
Abstract
Atorvastatin (ATV) is a well-established lipid-lowering agent. ATV has two stereogenic centers, and of the four possible stereoisomers, only the (3R,5R) form is used therapeutically. The European Pharmacopoeia (EP) monograph 2022 for ATV calcium salt describes a normal-phase high-performance
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Atorvastatin (ATV) is a well-established lipid-lowering agent. ATV has two stereogenic centers, and of the four possible stereoisomers, only the (3R,5R) form is used therapeutically. The European Pharmacopoeia (EP) monograph 2022 for ATV calcium salt describes a normal-phase high-performance liquid chromatography (HPLC) method for the determination of enantiomeric purity in both drug substance and working standard samples, based on a 150 mm × 4.6 mm Chiralpak AD-H column. The main problems with this method are the very long analysis time and the high solvent consumption. Here, an alternative chromatographic protocol was developed using the Chiralpak AD-3 column (250 mm × 4.6 mm) packed with 3 μm silica particles instead of the 5 μm silica particles of the Chiralpak AD-H chiral stationary phase and characterized by the same polysaccharide selector, amylose-tris(3,5-dimethylphenylcarbamate). Using a mobile phase consisting of a mixture of n-hexane-ethanol-formic acid 90:10:0.1 (v/v/v) as the mobile phase and setting the flow rate and column temperature to 1.0 mL min−1 and 35 °C, respectively, a simultaneous stereo-selective separation was achieved within 35 min without observing any overlap between the enantiomeric impurity peak and peaks related to other ATV impurities. Compared to HPLC EP conditions, the analysis time to elute all the potentially related substances was faster and significantly less mobile phase volume was required. The linearity of the method has been demonstrated in the range of 4.4 μg mL−1 to 1000 μg mL−1 (R2 > 0.999). At a concentration of 4.4 μg mL−1, which is 0.075% of the test solution (5.8 mg mL−1, as ATV free acid), the signal-to-noise ratio was found to be 20.
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(This article belongs to the Special Issue Application of Liquid Chromatography in Pharmaceutical and Toxicological Analysis)
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Open AccessArticle
Packed-Nanofiber Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography Fluorescence for Determining Gut Microbiota–Host Cometabolites and Indoleamines in Human Urine
by
Lanlan Wei and Xuejun Kang
Separations 2024, 11(5), 153; https://doi.org/10.3390/separations11050153 - 16 May 2024
Abstract
Exercise reduces the risk of inflammatory diseases by modulating different tissue and cell types, including those within the gastrointestinal tract. Obtaining a more comprehensive understanding of pathophysiology requires monitoring of dynamic changes in cometabolites. This study aimed to develop a method for determining
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Exercise reduces the risk of inflammatory diseases by modulating different tissue and cell types, including those within the gastrointestinal tract. Obtaining a more comprehensive understanding of pathophysiology requires monitoring of dynamic changes in cometabolites. This study aimed to develop a method for determining gut microbiota–host cometabolites and indoleamines in human urine. Four key gut microbiota–host cometabolites were chromatographically separated by isocratic elution, with a running time of 10 min. The linearity of this method was confirmed over different concentration ranges: 1.0–400 ng/mL for melatonin (MEL), indole-3-propionic acid (3-IPA), indole (IND), and skatole (SKT). This method was extremely sensitive and stable and hence could be successfully applied to characterize the changes in gut microbiota–host cometabolites in human before- and after-running urine. The concentrations of MEL, 3-IPA, IND, and SKT in after-running urine were 84.0 ± 9.69, 25.9 ± 3.39, 343.7 ± 36.8, and 14.6 ± 1.36 ng/mL, respectively. Moreover, the concentrations in before-running urine were 54.2 ± 5.10, 14.4 ± 1.30, 250.8 ± 14.1, and 9.43 ± 1.07 ng/mL, respectively, which showed significantly less difference in concentrations (p < 0.05) in before- than after-running urine. Overall, the established method could simultaneously monitor gut microbiota–host cometabolites and hence can be further applied to clinical and comprehensive pathophysiological studies.
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(This article belongs to the Special Issue Preparation of Membranes and Their Application in Separation)
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Open AccessReview
Research Progress in the Separation of Chemical Components from Essential Oils by High-Speed Countercurrent Chromatography
by
Linhong He, Zihao Zhong, Lijuan Zhang and Xi Bai
Separations 2024, 11(5), 152; https://doi.org/10.3390/separations11050152 - 15 May 2024
Abstract
Essential oils (EOs) are vital secondary metabolites in plants. They have garnered substantial attention owing to their distinct flavors and desirable attributes, including potent antioxidant, antibacterial, and antitumor properties. Nevertheless, the active constituents of EOs exhibit intricate chemical structures, and conventional separation techniques
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Essential oils (EOs) are vital secondary metabolites in plants. They have garnered substantial attention owing to their distinct flavors and desirable attributes, including potent antioxidant, antibacterial, and antitumor properties. Nevertheless, the active constituents of EOs exhibit intricate chemical structures, and conventional separation techniques are inadequate for purifying the individual chemical components from EOs. High-speed countercurrent chromatography, based on the principles of a hydrodynamic equilibrium system, has emerged as a liquid–liquid chromatographic separation method renowned for its ability to handle substantial single injection volumes and the absence of irreversible adsorption. Consequently, in recent years, this technique has been widely employed in the isolation and refinement of natural products. In this review, a comprehensive analysis is conducted, contrasting the merits and demerits of high-speed countercurrent chromatography with conventional separation methods. The solvent systems, elution modes, commonly employed detectors, and practical applications are reviewed in the context of high-speed countercurrent chromatography for essential oil separation and purification. Furthermore, this review offers a glimpse into the potential prospects of applying this technique, with the intention of serving as a valuable reference for the use of high-speed countercurrent chromatography in the purification of EOs.
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(This article belongs to the Special Issue HPLC or Other Chromatographic-Based Methods for Analysis of Bioactive Compounds in Plant, Food, and Pharmaceutical Products)
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Open AccessArticle
Feasibility of Different Methods for Separating n-Hexane and Ethanol
by
Aleksandra Sander, Ana Petračić, Marko Rogošić, Mirela Župan, Leonarda Frljak and Matija Cvetnić
Separations 2024, 11(5), 151; https://doi.org/10.3390/separations11050151 - 15 May 2024
Abstract
Conventional distillation methods cannot effectively separate the components of an azeotropic mixture since both phases have the same composition, thereby preventing further separation. Additional techniques such as pressure swing distillation or distillation with entrainers are often employed to overcome this limitation and achieve
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Conventional distillation methods cannot effectively separate the components of an azeotropic mixture since both phases have the same composition, thereby preventing further separation. Additional techniques such as pressure swing distillation or distillation with entrainers are often employed to overcome this limitation and achieve separation. The aim of this investigation was to select the most effective method for separating n-hexane and ethanol. The feasibility of three methods was analyzed: reduced pressure distillation, extractive distillation, and liquid–liquid extraction. The mutual solubility of n-hexane and prepared deep eutectic solvents (DESs) (nine hydrophilic: choline chloride with glycerol, ethylene glycol, or carboxylic acid (malic, citric, glycolic); tetramethylammonium chloride with glycolic acid; lactic acid with glycerol; K2CO3 with glycerol or ethylene glycol; two hydrophobic: menthol with decanoic or dodecanoic acid) was experimentally determined. Extraction experiments were conducted to test the solubility of DESs in the feed mixture. The effect of changing DES-to-feed mass ratio was further investigated with choline chloride–glycerol (1:2). The same DES and both hydrophobic DESs were able to increase the relative volatility and enhance the separation of ethanol and n-hexane. Based on the obtained results, extraction was selected as the most effective method for the separation of n-hexane and ethanol.
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(This article belongs to the Section Purification Technology)
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Open AccessArticle
Characterization of the SPIRITAS: A Disposable Sampling Setup for Volatile Organic Compound Collection and Analysis
by
David J. Mager, Yoni E. van Dijk, Özgü Varan, Susanne J. H. Vijverberg, Suzanne W. J. Terheggen-Lagro, Anke-Hilse Maitland-van der Zee, Hettie M. Janssens and Paul Brinkman
Separations 2024, 11(5), 150; https://doi.org/10.3390/separations11050150 - 14 May 2024
Abstract
Analyzing exhaled breath for volatile organic compounds (VOCs) using thermal desorption–gas chromatography–mass spectrometry (TD-GC-MS) offers a non-invasive diagnostic approach for various diseases. Despite its promise, the method faces challenges like sampling heterogeneity and high costs. Following the European Respiratory Society’s advocacy for methodological
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Analyzing exhaled breath for volatile organic compounds (VOCs) using thermal desorption–gas chromatography–mass spectrometry (TD-GC-MS) offers a non-invasive diagnostic approach for various diseases. Despite its promise, the method faces challenges like sampling heterogeneity and high costs. Following the European Respiratory Society’s advocacy for methodological standardization, we developed the SPIRITAS (Standardized Product for Inexpensive Respiratory InvesTigation: A breath Sampler), a low-cost, disposable breath sampler. This study evaluates the SPIRITAS’s effectiveness in detecting targeted VOCs. We tested the SPIRITAS using the Peppermint Experiment, a standardized protocol that allows for comparison between different breath sampling and analytical practices by assessing the ability to detect five peppermint-specific VOCs after ingestion of a 200-milligram peppermint oil capsule. We included ten subjects and performed six breath samples per participant, including a baseline measurement taken before ingestion. We used the Wilcoxon signed-rank test to evaluate whether baseline values were significantly lower than the peak values of the targeted VOCs. Additionally, we conducted an experiment utilizing humidified medical-grade air to identify any VOCs attributable to the SPIRITAS setup itself. Results showed successful detection of four out of five targeted “peppermint-associated” VOCs: alpha-pinene (p ≤ 0.01), beta-pinene (p ≤ 0.01), menthone (p = 0.01), and menthol (p = 0.02), indicating significant differences between the baseline and peak values in the volunteers’ breath. However, detection of eucalyptol was inconsistent. In addition, we identified 16 VOCs that were released by the SPIRITAS, one of which remains unidentified. Our findings underscore the SPIRITAS’s potential for clinical applications, paving the way for broader biomarker research. The combination of ease of use, low cost, reduced risk of contamination, and standardization makes SPIRITAS very suitable for large-scale international studies. Furthermore, we have demonstrated the SPIRITAS’s effectiveness in detecting specific VOCs and identified 16 compounds originating from the SPIRITAS, ensuring that these compounds would not be mis-qualified as potential biomarkers in future clinical studies.
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(This article belongs to the Section Chromatographic Separations)
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Open AccessEditor’s ChoiceArticle
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
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
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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.
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(This article belongs to the Section Purification Technology)
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