Next Issue
Volume 8, September
Previous Issue
Volume 8, July
 
 

Separations, Volume 8, Issue 8 (August 2021) – 23 articles

Cover Story (view full-size image): Proteins and peptides are primarily found in their L-form. Recent studies have shown that this homochirality is not guaranteed throughout life. Indeed, natural amino acid isomerization can be caused by an enzymatic or non-enzymatic process. The appearance of D-amino acids in proteins and peptides can influence human health and disease. Different chromatographic and electrophoretic techniques are developed for amino acid enantioseparation and the determination of chiral proteins and peptide sequences. View this paper.
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
Article
Quantification of Histidine-Containing Dipeptides in Dolphin Serum Using a Reversed-Phase Ion-Pair High-Performance Liquid Chromatography Method
Separations 2021, 8(8), 128; https://doi.org/10.3390/separations8080128 - 23 Aug 2021
Cited by 2 | Viewed by 1044
Abstract
The quantification of histidine-containing dipeptides (anserine, carnosine, and balenine) in serum might be a diagnostic tool to assess the health condition of animals. In this study, an existing reversed-phase ion-pair high-performance liquid chromatography (HPLC)–ultraviolet detection method was improved and validated to quantify serum [...] Read more.
The quantification of histidine-containing dipeptides (anserine, carnosine, and balenine) in serum might be a diagnostic tool to assess the health condition of animals. In this study, an existing reversed-phase ion-pair high-performance liquid chromatography (HPLC)–ultraviolet detection method was improved and validated to quantify serum anserine, carnosine, and balenine levels in the dolphin. The serum was deproteinized with trichloroacetic acid and directly injected into the HPLC system. Chromatographic separation of the three histidine-containing dipeptides was achieved on a TSK–gel ODS-80Ts (4.6 mm × 150 mm, 5 µm) analytical column using a mobile phase of 50 mmol/L potassium dihydrogen phosphate (pH 3.4) containing 6 mmol/L 1-heptanesulfonic acid and acetonitrile (96:4). The standard curve ranged from 0.1 µmol/L to 250 µmol/L. The average accuracy of the intra- and inter-analysis of anserine, carnosine, and balenine was 97–106%. The relative standard deviations of total precision (RSDr) of anserine, carnosine, and balenine in dolphin serum were 5.9%, 4.1%, and 2.6%, respectively. The lower limit of quantification of these compounds was 0.11–0.21 µmol/L. These results indicate that the improved method is reliable and concise for the simultaneous determination of anserine, carnosine, and balenine in dolphin serum, and may be useful for evaluation of health conditions in dolphins. Furthermore, this method can also be applied to other biological samples. Full article
(This article belongs to the Special Issue Separations in Biomedical Analysis)
Show Figures

Graphical abstract

Article
Multi-Objective Optimisation of Biodiesel Synthesis in Simulated Moving Bed Reactor
Separations 2021, 8(8), 127; https://doi.org/10.3390/separations8080127 - 21 Aug 2021
Viewed by 659
Abstract
In this work, multi-objective optimisation study was performed to determine the performance improvement in a simulated moving bed reactor (SMBR) for biodiesel synthesis. The selection of the operating parameters such as switching time, liquid flow rates in various sections, as well as the [...] Read more.
In this work, multi-objective optimisation study was performed to determine the performance improvement in a simulated moving bed reactor (SMBR) for biodiesel synthesis. The selection of the operating parameters such as switching time, liquid flow rates in various sections, as well as the length and number of columns is not straightforward in an SMBR. In most cases, conflicting requirements and constraints influence the optimal selection of the decision (operating or design) variables. A mathematical model that predicts single-column experimental results well was modified and verified experimentally for multiple-column SMBR system. In this article, a few multi-objective optimisation problems were carried out for both existing set-up as well as at the design stage. A non-dominated sorting genetic algorithm (NSGA) was used as the optimisation tool for the optimisation study. Due to conflicting effect of process parameters, the multi-objective optimisation study resulted in non-dominated Pareto optimal solutions. It was shown that significant increase in yield and purity of biodiesel in SMBR was possible both for operating and at design stage. Full article
(This article belongs to the Special Issue Adsorption Based Reactive-Separation Processes)
Show Figures

Figure 1

Article
Reusable Water Bottles: Release of Inorganic Elements, Phthalates, and Bisphenol A in a “Real Use” Simulation Experiment
Separations 2021, 8(8), 126; https://doi.org/10.3390/separations8080126 - 20 Aug 2021
Viewed by 969
Abstract
Reusable water bottles are growing in popularity; thus, possible chemical release from the internal surface into water should be carefully considered to control related health risks. We experimentally evaluated the release into deionized water of 40 elements, six phthalates, and bisphenol-A for 20 [...] Read more.
Reusable water bottles are growing in popularity; thus, possible chemical release from the internal surface into water should be carefully considered to control related health risks. We experimentally evaluated the release into deionized water of 40 elements, six phthalates, and bisphenol-A for 20 different reusable bottles by simulating the use in real world scenario. The 20 bottles, identified as those most purchased in Italy, were made of various materials (stainless steel, aluminum, plastic, and silicone). The experiment was carried out for four consecutive weeks in duplicate for each type of bottle. Our results showed the release, to various extents, of inorganic elements from all 20 bottles, while the release of phthalates and bisphenol-A was never found. The elements most frequently released were Al, Sr, Mo, and Cr, while the highest concentrations were for Ca, K, Mg, and Na; the release of toxic elements (such as Pb, Cd, Ni, Sb) also occurred. The comparison of our results with regulatory limits on drinking water quality revealed no exceeding values except for Al. However, these releases represent a further intake, and the related risks cannot be neglected, especially for highly susceptible populations. Thus, it is essential to correctly inform consumers both with dedicated interventions and exhaustive labelling. Full article
Show Figures

Graphical abstract

Article
Quantitation of Acetyl Hexapeptide-8 in Cosmetics by Hydrophilic Interaction Liquid Chromatography Coupled to Photo Diode Array Detection
Separations 2021, 8(8), 125; https://doi.org/10.3390/separations8080125 - 18 Aug 2021
Cited by 1 | Viewed by 914
Abstract
Bioactive peptides are gaining more and more popularity in the research and development of cosmetic products with anti-aging effect. Acetyl hexapeptide-8 is a hydrophilic peptide incorporated in cosmetics to reduce the under-eye wrinkles and the forehead furrows. Hydrophilic interaction liquid chromatography (HILIC) is [...] Read more.
Bioactive peptides are gaining more and more popularity in the research and development of cosmetic products with anti-aging effect. Acetyl hexapeptide-8 is a hydrophilic peptide incorporated in cosmetics to reduce the under-eye wrinkles and the forehead furrows. Hydrophilic interaction liquid chromatography (HILIC) is the separation technique of choice for analyzing peptides. In this work, a rapid HILIC method coupled to photodiode array detection operated at 214 nm was developed, validated and used to determine acetyl-hexapeptide-8 in cosmetics. Chromatography was performed on a Xbridge® HILIC BEH analytical column using as mobile phase a 40 mM ammonium formate water solution (pH 6.5)-acetonitrile mixture 30:70, v/v at flow rate 0.25 mL min−1. The assay was linear over the concentration range 20 to 30 μg mL−1 for the cosmetic formulations and 0.004 to 0.007% (w/w) for the cosmetic cream. The limits of quantitation for acetyl hexapeptide-8 were 1.5 μg mL−1 and 0.002% (w/w) for the assay of cosmetic formulations and cosmetic creams, respectively. The method was applied to the analysis of cosmetic formulations and anti-wrinkle cosmetic creams. Full article
(This article belongs to the Collection State of the Art in Separation Science)
Show Figures

Graphical abstract

Article
Efficient Sub-1 Minute Analysis of Selected Biomarker Catecholamines by Core-Shell Hydrophilic Interaction Liquid Chromatography (HILIC) with Nanomolar Detection at a Boron-Doped Diamond (BDD) Electrode
Separations 2021, 8(8), 124; https://doi.org/10.3390/separations8080124 - 18 Aug 2021
Viewed by 738
Abstract
A rapid, sensitive method for the separation of catecholamine biomarkers (CAs), of importance in traumatic brain injury (TBI) and in Parkinson’s disease (PD), has been successfully developed using hydrophilic interaction liquid chromatography (HILIC). Dopamine (DA), epinephrine (EPI), and norepinephrine (NE) are known to [...] Read more.
A rapid, sensitive method for the separation of catecholamine biomarkers (CAs), of importance in traumatic brain injury (TBI) and in Parkinson’s disease (PD), has been successfully developed using hydrophilic interaction liquid chromatography (HILIC). Dopamine (DA), epinephrine (EPI), and norepinephrine (NE) are known to be three to fivefold elevated above normal in traumatic brain injury (TBI) patients. HILIC facilitates the rapid and efficient separation of these polar biomarkers, which can be poorly retained by reversed-phase liquid chromatography (RPLC), while electrochemical detection (ECD) at the boron-doped diamond (BDD) electrode provides enhanced nanomolar detection. Three HILIC columns were compared, namely the superficially porous (core-shell) Z-HILIC column and the Z-cHILIC and Z-HILIC fully porous columns. The core-shell Z-HILIC showed the highest efficiency with a rapid separation within 60 s. The HILIC method utilizing the core-shell Z-HILIC column was initially optimized for the simultaneous analysis of DA, EPI, and NE using UV detection. The advantages of using the BDD electrode over UV detection were explored, and the improved limits of detection (LODs, S/N = 3) measured were 40, 50, and 50 nM for DA, EPI, and NE, respectively. Method validation is reported in terms of the linearity, repeatability, reproducibility, and LODs. Furthermore, the proposed method was successfully applied to the real sample analysis of urinary CAs following phenylboronic acid (PBA) solid phase extraction (SPE) pretreatment. Full article
(This article belongs to the Special Issue Chromatographic Analysis of Biological Samples)
Show Figures

Figure 1

Article
An Evaluation of the Antioxidant Activity of a Methanolic Extract of Cucumis melo L. Fruit (F1 Hybrid)
Separations 2021, 8(8), 123; https://doi.org/10.3390/separations8080123 - 18 Aug 2021
Cited by 1 | Viewed by 670
Abstract
Cucumis melo L. (C. melo) is a fruit with many medicinal properties and is consumed in various countries. It is utilised for chronic eczema and to treat minor burns and scrapes. The present study was conducted to evaluate the antioxidant activity [...] Read more.
Cucumis melo L. (C. melo) is a fruit with many medicinal properties and is consumed in various countries. It is utilised for chronic eczema and to treat minor burns and scrapes. The present study was conducted to evaluate the antioxidant activity of a methanolic extract of Cucumis melo Linn (MECM). A coarse powder prepared from the fruit and seeds was extracted with methanol (absolute) by a hot continuous percolation process in accordance with the standard protocols. All the extracts were estimated for potential antioxidant activities with tests such as an estimation of total antioxidant activity, hydroxyl radical and nitric oxide scavenging activity and reducing power ability. The qualitative analysis of the methanolic extract of C. melo fruit showed the presence of various phytochemical constituents such as carbohydrates, alkaloids, sterols, phenolic compounds, terpenes and flavonoids. The total antioxidant activity of concentrations of 50, 100 and 200 µg were tested and observed to be 3.3 ± 0.1732, 6.867 ± 0.5457 and 13.63 ± 0.8295 µg of ascorbic acid, respectively. The results also showed significant nitric oxide and DPPH scavenging activities as well as a reducing power activity of MECM. Thus, our results suggest that MECM may serve as a putative source of natural antioxidants for therapeutic and nutraceutical applications. Full article
(This article belongs to the Special Issue Extraction and Analysis of Plant Active Ingredients)
Show Figures

Figure 1

Article
Analysis of Floral Fragrance Compounds of Chimonanthus praecox with Different Floral Colors in Yunnan, China
Separations 2021, 8(8), 122; https://doi.org/10.3390/separations8080122 - 18 Aug 2021
Cited by 1 | Viewed by 963
Abstract
In order to better understand the floral fragrance compounds of Chimonanthus praecox belonging to genus Chimonanthus of Chimonanaceae in Yunnan, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was used to analyze these compounds from four C. praecox plants with different floral colors. [...] Read more.
In order to better understand the floral fragrance compounds of Chimonanthus praecox belonging to genus Chimonanthus of Chimonanaceae in Yunnan, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was used to analyze these compounds from four C. praecox plants with different floral colors. Thirty-one types of floral fragrance compounds were identified, among which terpenes, alcohols, esters, phenols, and heterocyclic compounds were the main compounds. Interestingly, the floral fragrance compounds identified in the flowers of C. praecox var. concolor included benzyl acetate, α-ocimene, eugenol, indole, and benzyl alcohol. By contrast, the floral fragrance compounds β-ocimene, α-ocimene, and trans-β-ocimene were detected in C. praecox var. patens. Cluster analysis showed that C. praecox var. concolor H1, H2, and C. praecox var. patens H4 were clustered in one group, but C. praecox var. patens H3 was individually clustered in the other group. Additionally, principal component analysis showed that α-ocimene, benzyl alcohol, benzyl acetate, cinnamyl acetate, eugenol, and indole were the main floral fragrance compounds that could distinguish the four C. praecox with different floral colors in Yunnan. This study provides a theoretical basis for further elucidating the mechanism and pathway of the floral fragrance release of C. praecox. Full article
Show Figures

Graphical abstract

Article
Particle Motion Characteristics in W-Shaped Hydrocyclones
Separations 2021, 8(8), 121; https://doi.org/10.3390/separations8080121 - 17 Aug 2021
Viewed by 589
Abstract
To investigate the multiphase flow characteristics and improve the classification mechanism of a W-shaped hydrocyclone, this paper adopts the numerical simulation method to evaluate the effects of the particle size and density on the separation characteristics and motion behavior of particles. Forces, such [...] Read more.
To investigate the multiphase flow characteristics and improve the classification mechanism of a W-shaped hydrocyclone, this paper adopts the numerical simulation method to evaluate the effects of the particle size and density on the separation characteristics and motion behavior of particles. Forces, such as the centrifugal inertia force, pressure gradient force and fluid drag force, which control particle motion, are analyzed, and the classification mechanism of W-shaped hydrocyclones is examined in terms of the particle distribution and separation efficiency. The results indicate that the radial centrifugal inertia and pressure gradient forces in W-shaped hydrocyclones are hundreds of times the gravity force, which is the main driver of radial motion. Particle density and size changes greatly impact the movement and distribution of coarse particles, but no notable change occurs in fine particles. With increasing particle density, the cut size decreases, and the fractionation accuracy increases. Full article
Show Figures

Figure 1

Article
Fluorescent Characteristics and Metal Binding Properties of Different Molecular Weight Fractions in Stratified Extracellular Polymeric Substances of Activated Sludge
Separations 2021, 8(8), 120; https://doi.org/10.3390/separations8080120 - 16 Aug 2021
Cited by 2 | Viewed by 607
Abstract
The combination of heavy metals and extracellular polymeric substances (EPSs) affects the distribution of heavy metals in microbial aggregates, soil, and aquatic systems. This paper aimed to explore the binding mechanisms of EPSs of different molecular weights in activated sludge with heavy metals. [...] Read more.
The combination of heavy metals and extracellular polymeric substances (EPSs) affects the distribution of heavy metals in microbial aggregates, soil, and aquatic systems. This paper aimed to explore the binding mechanisms of EPSs of different molecular weights in activated sludge with heavy metals. We extracted the stratification components of activated sludge EPSs and divided the components into five fractions of different molecular weight ranges. In the three-dimensional fluorescence analysis of each fraction, the EPSs of activated sludge had two peaks, peak A (representing low-excitation tryptophan) and peak B (representing high-excitation tryptophan), and static quenching was the main reason for the fluorescence quenching between the compounds attributable to peak A in activated sludge EPSs and Pb2+ and Cu2+. Further exploration suggested that the EPSs of activated sludge interacted with Cd2+, Pb2+, Cu2+, and Zn2+ to form new substances. The quenching effect of the EPSs with the highest molecular weight (100 kDa–0.7 μm) was more significant, and the binding ability was more stable. This study implies that the application of EPSs from activated sludge is promising. While effectively binding heavy metals, it can also reduce the volume of the excess activated sludge. Full article
(This article belongs to the Special Issue Sustainable Water and Wastewater Purification Technologies)
Show Figures

Figure 1

Article
ICP–MS Analysis of Multi-Elemental Profile of Greek Wines and Their Classification According to Variety, Area and Year of Production
Separations 2021, 8(8), 119; https://doi.org/10.3390/separations8080119 - 13 Aug 2021
Cited by 1 | Viewed by 1114
Abstract
Major, minor and trace elements in wines from Greece were determined by inductively coupled plasma–mass spectrometry (ICP–MS). The concentrations of 44 elements (Na, Mg, P, K, Ca, Cu, Co, Cr, Zn, Sn, Fe, Mn, Li, Be, B, V, Sr, Ba, Al, Ag, Ni, [...] Read more.
Major, minor and trace elements in wines from Greece were determined by inductively coupled plasma–mass spectrometry (ICP–MS). The concentrations of 44 elements (Na, Mg, P, K, Ca, Cu, Co, Cr, Zn, Sn, Fe, Mn, Li, Be, B, V, Sr, Ba, Al, Ag, Ni, As, Sn, Hg, Pb, Sb, Cd, Ti, Ga, Zr, Nb, Pd, Te, La, Sm, Ho, Tm, Yb, W, Os, Au, Tl, Th, U) in 90 white and red wines from six different regions in Greece for two consecutive vinification years, 2017 and 2018, were determined. Results for the elements aforementioned were evaluated by multivariate statistical methods, such as discriminant analysis and cluster analysis, and the wines were discriminated according to wine variety and geographical origin. Due to the specific choice of the analytes for multivariate statistical investigation, a prediction rate by cross-validation of 98% could be achieved. The aim of this study was not only to reveal specific relationships between the wine samples or between the chemical variables in order to classify the wines from different regions and varieties according to their elemental profile (wine authentication), but also to observe the annual fluctuation in the mineral content of the studied wine samples. Full article
Show Figures

Figure 1

Article
Simultaneous Determination of C18 Fatty Acids in Milk by GC-MS
Separations 2021, 8(8), 118; https://doi.org/10.3390/separations8080118 - 11 Aug 2021
Cited by 1 | Viewed by 907
Abstract
The determination of C18 fatty acids (FAs) is a key and difficult aspect in FA profiling, and a qualified method with good chromatographic separation and high sensitivity, as well as easy methylation, is required. A GC-MS method was established to simultaneously determine C18 [...] Read more.
The determination of C18 fatty acids (FAs) is a key and difficult aspect in FA profiling, and a qualified method with good chromatographic separation and high sensitivity, as well as easy methylation, is required. A GC-MS method was established to simultaneously determine C18 FAs in milk. To simplify the methylation protocol for milk samples, besides a base-catalyzation methylation (50 °C for 20 min), the necessity of an additional acid-catalyzation was also studied using different temperatures (60 °C, 70 °C, 80 °C, and 90 °C) and durations (90 min and 150 min). The results showed that the chromatographic resolution was improved, although three co-eluted peaks existed. The base-catalyzation was sufficient, and an additional acid-catalyzation was not necessary. The proposed method was validated with good sensitivity, linearity, accuracy, and precision, and then applied in determining C18 FAs in 20 raw milk and 30 commercial milk samples. UHT milk presented a different profile of C18 FAs from raw milk and PAS milk samples, which indicated that excessive heating could change the profile. Overall, the proposed method is a high-throughput and competent approach for the determination of C18 FAs in milk, and which presents an improvement in chromatographic resolution and sensitivity, as well as a simplification of methylation. Full article
(This article belongs to the Section Analysis of Food and Beverages)
Show Figures

Graphical abstract

Article
Determination of Lidocaine in Postmortem Whole Blood Samples after Unsuccessful Cardiopulmonary Resuscitation
Separations 2021, 8(8), 117; https://doi.org/10.3390/separations8080117 - 09 Aug 2021
Viewed by 643
Abstract
Forensic toxicologists often detect lidocaine in the biological fluids of the deceased, due to cardiopulmonary resuscitation (CPR) attempts prior to death. Here, we describe the development of a rapid, sensitive and robust method for the detection of lidocaine in postmortem whole blood using [...] Read more.
Forensic toxicologists often detect lidocaine in the biological fluids of the deceased, due to cardiopulmonary resuscitation (CPR) attempts prior to death. Here, we describe the development of a rapid, sensitive and robust method for the detection of lidocaine in postmortem whole blood using liquid−liquid extraction (LLE) followed by GC/MS analysis. The method showed a dynamic linear range of 100 to 6000 ng/mL with a linearity expressed by the regression coefficient (R2) and a value of 0.9947. The quantitation limit (LOQ) was found to be 0.03 ng/mL and the detection limit (LOD) 0.01 ng/mL. Recovery accuracy and repeatability were satisfactory. Finally, the method was applied to 23 real whole blood samples from cases where CPR was attempted. Blood concentrations ranged from 0.21–0.96 μg/mL. Full article
(This article belongs to the Special Issue Application of Chromatography in Forensic Toxicology and Pharmacology)
Show Figures

Figure 1

Article
Evaluation of High Resolution Melting (HRM) Analysis for Meat Species Identification of Raw and Cooked Meat
Separations 2021, 8(8), 116; https://doi.org/10.3390/separations8080116 - 08 Aug 2021
Viewed by 764
Abstract
The current study aimed to examine a real-time PCR assay with high-resolution melting (HRM) analysis for the species identification of minced meat samples. Meat samples from several animal species were purchased and minced separately or as a mixture of two species. DNA was [...] Read more.
The current study aimed to examine a real-time PCR assay with high-resolution melting (HRM) analysis for the species identification of minced meat samples. Meat samples from several animal species were purchased and minced separately or as a mixture of two species. DNA was extracted from all meat samples and subjected to real-time PCR assay by amplifying species-specific mitochondrial cytochrome b regions. Regarding the meat mixtures, two separate melting curves with specific melt peak temperatures (Tm) were detected. Additionally, DNA from each species was quantified, based on the calibration curves. The results showed that a real-time PCR assay with HRM analysis is suitable for the species identification of meat products, and could be used for the detection of meat frauds. Full article
Show Figures

Figure 1

Article
Supercritical Carbon Dioxide Extraction, Antioxidant Activity, and Fatty Acid Composition of Bran Oil from Rice Varieties Cultivated in Portugal
Separations 2021, 8(8), 115; https://doi.org/10.3390/separations8080115 - 05 Aug 2021
Cited by 1 | Viewed by 796
Abstract
Bran of different rice cultivars produced in Portugal were used to study supercritical carbon dioxide extraction conditions of rice bran oil (RBO) and evaluate and compare antioxidant activity and fatty acid composition of the different rice bran varieties. The effect of plant loading [...] Read more.
Bran of different rice cultivars produced in Portugal were used to study supercritical carbon dioxide extraction conditions of rice bran oil (RBO) and evaluate and compare antioxidant activity and fatty acid composition of the different rice bran varieties. The effect of plant loading (10–20 g), CO2 flow rate (0.5–1.5 L/min), pressure (20–60 MPa), and temperature (40–80 °C) was studied. The amount of oil extracted ranged from 11.72%, for Ariete cultivar, to 15.60%, for Sirio cultivar. The main fatty acids components obtained were palmitic (13.37%–16.32%), oleic (44.60%–52.56%), and linoleic (29.90%–38.51%). Excellent parameters of the susceptibility to oxidation of the oils were obtained and compare. RBO of Ariete and Gladio varieties presented superior DPPH and ABTS radical scavenging activities, whereas, Minima, Ellebi, and Sirio varieties had the lowest scavenging activities. Moreover, the oil obtained towards the final stages of extraction presented increased antioxidant activity. Full article
Show Figures

Graphical abstract

Article
Chemical Profiling, Antioxidant, Antiproliferative, and Antibacterial Potentials of Chemically Characterized Extract of Citrullus colocynthis L. Seeds
Separations 2021, 8(8), 114; https://doi.org/10.3390/separations8080114 - 04 Aug 2021
Cited by 11 | Viewed by 1044
Abstract
Background: Citrullus colocynthis L. (C. colocynthis) is commonly known as colocynth. It belongs to the family Cucurbitaceae that is frequently used in alternative medicine in the north of Africa. The aim of the study: the present research was undertaken to investigate [...] Read more.
Background: Citrullus colocynthis L. (C. colocynthis) is commonly known as colocynth. It belongs to the family Cucurbitaceae that is frequently used in alternative medicine in the north of Africa. The aim of the study: the present research was undertaken to investigate the chemical composition, antioxidant, antiproliferative, and antibacterial potentials of C. colocynthis seed extract. Material and methods: the chemical composition of C. colocynthis seed organic extract was characterized using gas chromatography/mass spectrometry (GC-MS). The antioxidant property was carried out using both β-carotene bleaching and DPPH assays. The antibacterial effect was effectuated using the agar disc diffusion method. The antiproliferative activity vs. human colorectal adenocarcinoma cell line (HT-29) and human breast adenocarcinoma cell line (MDA MB 231) were carried by WST-1 test. The chemical analysis showed the presence of interesting potentially bioactive compounds. The studied plant extract exhibited antioxidant potential with IC50 value of 2. 22 mg/mL (β-carotene bleaching) and 8.98 ± 0.619 mg/mL (DPPH). Concerning the antiproliferative activity, the seed extract was effective in MDA-MB-231 and HT-29 cancer cells with IC50 values 86.89 ± 3.395 and 242.1 ± 17.9 μg/mL, respectively, whilst the extract of Citrullus colocynthis seeds was non-toxic in healthy human dermal fibroblasts. Regarding the antibacterial test, the extract was effective in Gram-positive bacteria only. Conclusion: The outcome of this research indicated that the extracts from C. colocynthis seeds may compose a promising source with interesting compounds that can be used to fight cancer, free radicals damage, and bacterial infections. Full article
Show Figures

Figure 1

Article
Applying a Hydrophilic Modified Hollow Fiber Membrane to Reduce Fouling in Artificial Lungs
Separations 2021, 8(8), 113; https://doi.org/10.3390/separations8080113 - 30 Jul 2021
Viewed by 766
Abstract
Membranes for use in high gas exchange lung applications are riddled with fouling. The goal of this research is to create a membrane that can function in an artificial lung until the actual lung becomes available for the patient. The design of the [...] Read more.
Membranes for use in high gas exchange lung applications are riddled with fouling. The goal of this research is to create a membrane that can function in an artificial lung until the actual lung becomes available for the patient. The design of the artificial lung is based on new hollow fiber membranes (HFMs), due to which the current devices have short and limited periods of low fouling. By successfully modifying membranes with attached peptoids, low fouling can be achieved for longer periods of time. Hydrophilic modification of porous polysulfone (PSF) membranes can be achieved gradually by polydopamine (PSU-PDA) and peptoid (PSU-PDA-NMEG5). Polysulfone (PSU-BSA-35Mg), polysulfone polydopamine (PSUPDA-BSA-35Mg) and polysulfone polydopamine peptoid (PSU-PDA-NMEG5-BSA35Mg) were tested by potting into the new design of gas exchange modules. Both surfaces of the modified membranes were found to be highly resistant to protein fouling permanently. The use of different peptoids can facilitate optimization of the low fouling on the membrane surface, thereby allowing membranes to be run for significantly longer time periods than has been currently achieved. Full article
(This article belongs to the Special Issue Modeling, Simulation, and Optimization of Membrane Processes)
Show Figures

Figure 1

Review
Recent Advances in Chiral Analysis of Proteins and Peptides
Separations 2021, 8(8), 112; https://doi.org/10.3390/separations8080112 - 29 Jul 2021
Cited by 4 | Viewed by 1180
Abstract
Like many biological compounds, proteins are found primarily in their homochiral form. However, homochirality is not guaranteed throughout life. Determining their chiral proteinogenic sequence is a complex analytical challenge. This is because certain d-amino acids contained in proteins play a role in [...] Read more.
Like many biological compounds, proteins are found primarily in their homochiral form. However, homochirality is not guaranteed throughout life. Determining their chiral proteinogenic sequence is a complex analytical challenge. This is because certain d-amino acids contained in proteins play a role in human health and disease. This is the case, for example, with d-Asp in elastin, β-amyloid and α-crystallin which, respectively, have an action on arteriosclerosis, Alzheimer’s disease and cataracts. Sequence-dependent and sequence-independent are the two strategies for detecting the presence and position of d-amino acids in proteins. These methods rely on enzymatic digestion by a site-specific enzyme and acid hydrolysis in a deuterium or tritium environment to limit the natural racemization of amino acids. In this review, chromatographic and electrophoretic techniques, such as LC, SFC, GC and CE, will be recently developed (2018–2020) for the enantioseparation of amino acids and peptides. For future work, the discovery and development of new chiral stationary phases and derivatization reagents could increase the resolution of chiral separations. Full article
(This article belongs to the Special Issue Separations and Analysis of Proteins in Biological Samples)
Show Figures

Graphical abstract

Article
A Tapered Capillary-Based Contactless Atmospheric Pressure Ionization Mass Spectrometry for On-Line Preconcentration and Separation of Small Organics
Separations 2021, 8(8), 111; https://doi.org/10.3390/separations8080111 - 29 Jul 2021
Cited by 3 | Viewed by 774
Abstract
Capillary electrophoresis (CE) is an effective technique for the separation of different analytes. Moreover, online preconcentration of trace analytes in the capillary for CE analysis has been demonstrated. CE and capillary electrochromatography (CEC) are suitable for the separation of analytes with similar polarities. [...] Read more.
Capillary electrophoresis (CE) is an effective technique for the separation of different analytes. Moreover, online preconcentration of trace analytes in the capillary for CE analysis has been demonstrated. CE and capillary electrochromatography (CEC) are suitable for the separation of analytes with similar polarities. Given that CE and CEC are only used to separate small-volume samples, sensitive mass spectrometry (MS) is a suitable detection tool for CE and CEC. Contactless atmospheric pressure ionization (C-API) is a continuous flow ion source that only uses a short capillary as the ionization emitter operated at atmospheric pressure for MS analysis. In this study, we demonstrated the feasibility of hyphenating CE/CEC with C-API-MS by using a short and tapered capillary as the interface. The short capillary (a few centimeters) can function as the separation/preconcentration tube and the ionization emitter. This hyphenated technique can be used to analyze small organics within a few minutes. The suitability of using the hyphenated technique for online preconcentration, separation, and quantitative analysis for small organics is demonstrated in this study. Full article
Show Figures

Graphical abstract

Article
Quantitative Capillary Electrophoresis for Analysis of Extracellular Vesicles (EVqCE)
Separations 2021, 8(8), 110; https://doi.org/10.3390/separations8080110 - 29 Jul 2021
Cited by 1 | Viewed by 961
Abstract
Extracellular Vesicles (EVs) gained significant interest within the last decade as a new source of biomarkers for the early detection of diseases and a promising tool for therapeutic applications. In this work, we present Extracellular Vesicles Quantitative Capillary Electrophoresis (EVqCE) to measure an [...] Read more.
Extracellular Vesicles (EVs) gained significant interest within the last decade as a new source of biomarkers for the early detection of diseases and a promising tool for therapeutic applications. In this work, we present Extracellular Vesicles Quantitative Capillary Electrophoresis (EVqCE) to measure an average mass of RNA in EVs, determine EV concentrations and the degree of EV degradation after sample handling. We used EVqCE to analyze EVs isolated from conditioned media of three cancer cell lines. EVqCE employs capillary zone electrophoresis with laser-induced fluorescent detection to separate intact EVs from free nucleic acids. After lysis of EVs with a detergent, the encapsulated nucleic acids are released. Therefore, the initial concentration of intact EVs is calculated based on a nucleic acid peak gain. EVqCE works in a dynamic range of EV concentrations from 108 to 1010 particles/mL. The quantification process can be completed in less than one hour and requires minimum optimization. Furthermore, the average mass of RNA was found to be in the range of 200–400 ag per particle, noting that more aggressive cancer cells have less RNA in EVs (200 ag per particle) than non-aggressive cancer cells (350 ag per particle). EVqCE works well for the degradation analysis of EVs. Sonication for 10 min at 40 kHz caused 85% degradation of EVs, 10 freeze-thaw cycles (from −80 °C to 22 °C) produced 40%, 14-day storage at 4 °C made 32%, and vortexing for 5 min caused 5% degradation. Presently, EVqCE cannot separate and distinguish individual EV populations (exosomes, microvesicles, apoptotic bodies) from each other. Still, it is tolerant to the presence of non-EV particles, protein-lipid complexes, and protein aggregates. Full article
(This article belongs to the Special Issue Analysis of Metabolites in Biological Fluids)
Show Figures

Figure 1

Article
A Rapid Analytical Approach for Monitoring Pharmaceuticals in Hospital Wastewater—A DPX-Based Procedure with Environmentally-Friendly Extraction Phase Coupled to High Performance Liquid Chromatography–Diode Array/Fluorescence Detectors
Separations 2021, 8(8), 109; https://doi.org/10.3390/separations8080109 - 29 Jul 2021
Cited by 1 | Viewed by 656
Abstract
In this study, a novel analytical methodology based on disposable pipette extraction (DPX) was developed using an alternative extraction phase for the extraction/determination of six pharmaceutical compounds, including carbamazepine, diclofenac, naproxen, fluoxetine, losartan and 17α-ethinylestradiol, in samples of hospital wastewater by high-performance liquid [...] Read more.
In this study, a novel analytical methodology based on disposable pipette extraction (DPX) was developed using an alternative extraction phase for the extraction/determination of six pharmaceutical compounds, including carbamazepine, diclofenac, naproxen, fluoxetine, losartan and 17α-ethinylestradiol, in samples of hospital wastewater by high-performance liquid chromatography coupled to diode array and fluorescence detectors. The performance of three extraction phases was examined, including 3-n-propyl (3-methylpyridinium) silsesquioxane chloride (Si3Py+Cl), the conductive polymer polypyrrole (PPy), and polypyrrole modified with cetyltrimethylammonium bromide (PPy.CTAB). The optimization of the experimental parameters was performed through univariate and multivariate approaches. The optimized condition was obtained with the use of 20 mg of Si3Py+Cl as extraction phase; six extraction cycles with 700 μL of sample in each cycle and 15 s of extraction time; three desorption cycles with 100 μL of ACN (same aliquot) and 15 s of desorption time; and sample pH adjusted at 3.5 and addition of 15% (w/v) of NaCl in the sample. The methodology proposed exhibited environmentally-friendly aspects with a significantly reduced volume of organic solvent (only 100 µL) and a small amount of extraction phase (20 mg). In addition, the extraction phase employed exhibits a simple synthetic procedure, low cost, and high stability in organic solvent. Moreover, the method developed exhibits high throughput (extraction time of 6.5 min per sample), and robustness. The analytical figures of merit were obtained using hospital wastewater, and the values were very satisfactory. The correlation coefficients were higher than 0.9710. LODs and LOQs ranged from 0.030 µg L−1 to 1.510 µg L−1 and 0.10 µg L−1 to 5.00 µg L−1, respectively. Relative recoveries varied from 80 to 127%, and intra-day (n = 3) and inter-day (n = 9) precision was lower than 19%. Full article
Show Figures

Figure 1

Article
Silver Nanoparticles Functionalized with Sodium Mercaptoethane Sulfonate to Remove Copper from Water by the Formation of a Micellar Phase
Separations 2021, 8(8), 108; https://doi.org/10.3390/separations8080108 - 29 Jul 2021
Viewed by 612
Abstract
This work presents a novel procedure for the removal of Cu2+ from water, an essential element in human nutrition considered toxic in high concentrations, based on a microextraction technique involving the formation of a micellar phase. To achieve the total elimination of [...] Read more.
This work presents a novel procedure for the removal of Cu2+ from water, an essential element in human nutrition considered toxic in high concentrations, based on a microextraction technique involving the formation of a micellar phase. To achieve the total elimination of copper from aqueous samples, a Cu2+-complexing reagent based on silver nanoparticles functionalized with sodium mercaptoethane sulfonate ([email protected]) was used. The complex formed by Cu2+ and the reagent was extracted into a micellar microphase formed by Triton X-114, a harmless surfactant. Volumes of 200 µL of the 10−4 mol L−1 suspension of [email protected] and 100 µL of a solution of Triton X-114 at 30% m/m were employed to successfully remove 10 mg L−1 of Cu from 20 mL of water samples. The time and temperature needed to achieve 100% microextraction efficiency were 10 min and 40 °C, respectively. The procedure is considered environmentally friendly due to the low volume of the extracting phase and the simple experimental conditions that achieve total removal of Cu2+ from water samples. Full article
Show Figures

Figure 1

Article
Adsorption Characteristics and Mechanism of Calcium Ions on Different Molybdenite Surfaces via Experiments and DFT Simulations
Separations 2021, 8(8), 107; https://doi.org/10.3390/separations8080107 - 24 Jul 2021
Cited by 1 | Viewed by 728
Abstract
Calcium ions are common in flotation process water, and have a significant effect on the molybdenite floatability, making separation of molybdenite from other minerals more difficult. Therefore, to improve the separation selectivity, the research of how calcium ions affect the molybdenite surface properties [...] Read more.
Calcium ions are common in flotation process water, and have a significant effect on the molybdenite floatability, making separation of molybdenite from other minerals more difficult. Therefore, to improve the separation selectivity, the research of how calcium ions affect the molybdenite surface properties is of great significance. In this study, various methods including flotation tests, contact angle measurements, batch adsorption tests and Density Functional Theory (DFT) simulations were carried out to understand the adsorption characteristics and mechanism. Results of the contact angle measurements showed that the inhibition effects of calcium ions on molybdenite flotation kinetics were mostly attributed to the decrease of the edge surface hydrophobicity, as the contact angle of the edge surface decreased more than the face surface after treatment with calcium ions. While fitting the results of batch adsorption tests with adsorption kinetics and isotherm models, it was found that the Lagergen pseudo-first-order equation and the Freundlich isotherm model nicely follow the experimental trend. Moreover, DFT calculation results indicated that both Ca2+ and CaOH+ preferentially adsorb on the molybdenite (100) surface, particularly the edge surface, which was consistent with the contact angle results. Ca2+ adsorbed on the Mo-top site on the S-(100) surface by forming Ca-S bonds, transferring electrons from Ca 3d orbitals to S 3p orbitals. CaOH+ adsorbed on the S-top site of Mo-(100) surface by forming a strong covalent Mo-O bond and S-Ca bond. The results provide a basis for understanding and improving the separation effect of molybdenite from other minerals in the presence of calcium ions. Full article
Show Figures

Figure 1

Article
Development of a Modified QuEChERS Procedure for the Isolation of Pesticide Residues from Textile Samples, Followed by GC–MS Determination
Separations 2021, 8(8), 106; https://doi.org/10.3390/separations8080106 - 23 Jul 2021
Cited by 2 | Viewed by 775
Abstract
Due to the use of pesticides during cotton production and/or textile storage, it is necessary to assure textile and clothing safety in order to improve the protection of human health. In this work, an efficient method was established for a multiresidue determination of [...] Read more.
Due to the use of pesticides during cotton production and/or textile storage, it is necessary to assure textile and clothing safety in order to improve the protection of human health. In this work, an efficient method was established for a multiresidue determination of 33 pesticides covering several pesticide classes such as organochlorine, organophosphate, pyrethroides, triazines, etc., in textiles by modified QuEChERS and followed by gas chromatography–mass spectrometry. Optimal conditions were selected, including the amount of the sample, type of the extraction solvent and cleaning up sorbents, until the method was finally validated. Sufficient accuracy and precision were presented by the method using spiked samples between 10 and 250 μg/kg, while recoveries from 70 to 120% and an RSD < 20% for all the pesticides were obtained; the limits of quantification were below 5 μg/kg for all studied pesticides. The presented method showed high separation efficiency with minimal sample and sorbent consumption. The validated method was successfully applied to the analysis of real samples and proved to be applicable to routine analyses. Full article
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop