Next Issue
Volume 8, January
Previous Issue
Volume 7, September

Separations, Volume 7, Issue 4 (December 2020) – 26 articles

Cover Story (view full-size image): Nanoliquid chromatography has enabled the enantiomeric separation of two chiral drugs, lacosamide and colchicine, in less than 8 and 9 min with enantiomeric resolutions of 1.6 and 2.3, respectively. A capillary column lab-packed with an amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phase was used. This methodology is characterized by the low volume of mobile phase and sample required (1.8 µL per analysis and 20 nL sample). The proposed method can detect the enantiomeric impurities of both drugs up to a 0.1% with respect to the majority enantiomer and can successfully be applied to ensure quality control of these drugs in pharmaceutical formulations. 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
Solid-Phase Microextraction Arrow for the Sampling of Volatile Organic Compounds in Milk Samples
Separations 2020, 7(4), 75; https://doi.org/10.3390/separations7040075 - 18 Dec 2020
Cited by 4 | Viewed by 1240
Abstract
A novel sample preparation method based on the use of the Arrow solid-phase microextraction device was used to extract and preconcentrate volatile organic compounds (VOCs) from milk samples prior to their determination by gas chromatography–mass spectrometry (GC-MS). The experimental parameters of the solid-phase [...] Read more.
A novel sample preparation method based on the use of the Arrow solid-phase microextraction device was used to extract and preconcentrate volatile organic compounds (VOCs) from milk samples prior to their determination by gas chromatography–mass spectrometry (GC-MS). The experimental parameters of the solid-phase microextraction (SPME) Arrow method were evaluated in terms of fiber type, sample volume, extraction temperature, extraction time, stirring rate and salt addition. Under the optimum extraction conditions, the SPME Arrow was compared with conventional SPME fibers to evaluate the effectiveness of the SPME Arrow method. Evaluation of the conventional SPME procedure was also performed under optimized conditions, for appropriate method comparison. Due to the larger sorption phase volume of SPME Arrow, a higher sensitivity and reproducibility were observed for the determined chromatographic peaks in comparison with conventional SPME fibers. The use of Carbon wide range (WR) SPME Arrow/polydimethylsiloxane (CAR/PDMS) SPME Arrow fibers leads to a compound-dependent improvement of a factor of 4–5x over the classical SPME setup. Moreover, the relative standard deviation (RSD) of the total volatiles for a conventional SPME procedure was 12.5%, while for SPME Arrow it was 6.2%. Finally, the novel method was successfully employed for the analysis of commercially available milk samples. The findings of this study indicate that SPME Arrow can be effectively used for the determination of volatile organic compounds in complex food matrixes. Full article
Show Figures

Figure 1

Article
Selective TiO2 Phosphopeptide Enrichment of Complex Samples in the Nanogram Range
Separations 2020, 7(4), 74; https://doi.org/10.3390/separations7040074 - 17 Dec 2020
Cited by 1 | Viewed by 846
Abstract
Phosphopeptide enrichment is a commonly used sample preparation step for investigating phosphorylation. TiO2-based enrichment has been demonstrated to have excellent performance both for large amounts of complex and for small amounts of simple samples. However, it has not yet been studied [...] Read more.
Phosphopeptide enrichment is a commonly used sample preparation step for investigating phosphorylation. TiO2-based enrichment has been demonstrated to have excellent performance both for large amounts of complex and for small amounts of simple samples. However, it has not yet been studied for complex samples in the nanogram range. Our objective was to develop a methodology applicable for complex samples in the low nanogram range, useful for mass spectrometry analysis of tissue microarrays. The selectivity and performance of two stationary phases (TiO2 nanoparticle-coated monolithic column and spin tip filled with TiO2 microspheres) and several loading solvents were studied. Based on this study, we developed an effective and robust method, based on a spin tip with a non-conventional 50 mM citric acid-based loading solvent. It gave excellent results for phosphopeptide enrichment from samples containing a few nanograms of a complex protein mixture. Full article
Show Figures

Graphical abstract

Article
Separation of the Glycosylated Carotenoid Myxoxanthophyll from Synechocystis Salina by HPCCC and Evaluation of Its Antioxidant, Tyrosinase Inhibitory and Immune-Stimulating Properties
Separations 2020, 7(4), 73; https://doi.org/10.3390/separations7040073 - 15 Dec 2020
Cited by 6 | Viewed by 1469
Abstract
Global demand for natural pigments has increased in the past few years. Myxoxanthophyll, a glycosylated monocyclic carotenoid, is a pigment that occurs naturally in cyanobacteria but no scalable isolation process has been developed to obtain it from its natural source to date. In [...] Read more.
Global demand for natural pigments has increased in the past few years. Myxoxanthophyll, a glycosylated monocyclic carotenoid, is a pigment that occurs naturally in cyanobacteria but no scalable isolation process has been developed to obtain it from its natural source to date. In this study, myxoxanthophyll was isolated from unicellular cyanobacterium Synechocystis salina (S. salina) using high-performance countercurrent chromatography (HPCCC), where the lower phase of the biphasic solvent system composed of n-heptane–ethanol–water (2:4:4, v/v/v) was used as a mobile phase, whereas its upper phase was the stationary phase. For the HPCCC isolation, a multi-injection method was developed, and four consecutive sample injections (70 mg each) were performed, obtaining, in total, 20 mg of myxoxanthophyll, which was finally purified with high-performance liquid chromatography (HPLC). Overall, a final myxoxanthophyll yield of 15 mg (98% purity) was obtained. The target pigment showed a weak antioxidant and tyrosinase inhibitory effect, and exhibited immune-stimulating properties by activating human granulocytes. The results presented here form a basis for the large-scale production of myxoxanthophyll, and show the potential benefits of this pigment for human health. Full article
(This article belongs to the Special Issue Applications of Liquid–Liquid Chromatography)
Show Figures

Graphical abstract

Article
Determination of Carminic Acid in Foodstuffs and Pharmaceuticals by Microchip Electrophoresis with Photometric Detection
Separations 2020, 7(4), 72; https://doi.org/10.3390/separations7040072 - 13 Dec 2020
Cited by 5 | Viewed by 1169
Abstract
This paper presents a novel miniaturized analytical method for the determination of carminic acid, a natural red food dye, in complex food and pharmaceutical matrices by microchip electrophoresis (MCE) with photometric detection. MCE has become a very attractive microscale separation technique because it [...] Read more.
This paper presents a novel miniaturized analytical method for the determination of carminic acid, a natural red food dye, in complex food and pharmaceutical matrices by microchip electrophoresis (MCE) with photometric detection. MCE has become a very attractive microscale separation technique because it offers high-speed, high-throughput, small sample injection volume and low reagents consumption. Fast determination of carminic acid in less than 5 min was achieved on a poly(methyl methacrylate) microchip in anionic separation mode at pH 6. Photometric detector based on light-emitting diode technology was set to a wavelength of 490 nm. Using a sample injection volume of 900 nL, a limit of detection of 69 nmol L−1 was achieved. A wide linear dynamic range over four orders of magnitude (from nmol L−1 to mmol L−1) was observed for peak area. Developed method provided favorable intra- and inter-day repeatability of the migration time (up to 2.5% RSD), as well as the repeatability of the peak area (less than 1.9% RSD), regardless of the sample type. The content of carminic acid was determined in various foodstuffs and pharmaceuticals, such as candies, saffron, non-alcoholic drink, and sore throat lozenges with good recoveries (92.5–104.0%). Full article
(This article belongs to the Special Issue Capillary and Microchip Electrophoresis for Bioanalysis)
Show Figures

Graphical abstract

Article
Synthesis and Characterization of B/NaF and Silicon Phthalocyanine-Modified TiO2 and an Evaluation of Their Photocatalytic Removal of Carbamazepine
Separations 2020, 7(4), 71; https://doi.org/10.3390/separations7040071 - 10 Dec 2020
Cited by 6 | Viewed by 898
Abstract
This study investigated the synthesis of two different types of photocatalysts, namely, boron/sodium fluoride co-doped titanium dioxide (B/NaF-TiO2), and its analogue, a dye-sensitized form of silicon-based axial methoxy substituted phthalocyanine (B/NaF-TiO2SiPc). Structural and morphological characterizations were performed via X-ray [...] Read more.
This study investigated the synthesis of two different types of photocatalysts, namely, boron/sodium fluoride co-doped titanium dioxide (B/NaF-TiO2), and its analogue, a dye-sensitized form of silicon-based axial methoxy substituted phthalocyanine (B/NaF-TiO2SiPc). Structural and morphological characterizations were performed via X-ray diffraction (XRD); Fourier transform infra-red (FTIR); N2 adsorption–desorption at 77 K by Brunauer–Emmett–Teller (BET) and Barrett, Joyner, and Halenda (BJH) methods; transmission electron microscopy (TEM); X-ray photoelectron spectroscopy (XPS); and UV–visible absorption spectroscopy. The estimated crystallite size of pure TiO2 and pure B/NaF-TiO2 was 24 nm, and that of B/NaF-TiO2SiPc was 29 nm, whereas particle sizes determined by TEM were 25, 28, and 31 nm for pure TiO2, B/NaF-TiO2 and B/NaF-TiO2SiPc respectively. No significant differences between B/NaF-TiO2 and B/NaF-TiO2SiPc were observed for surface area by (BET) analysis (13 m2/g) or total pore volume by the BJH application model (0.05 cm3/g). Energy band gap values obtained for B/NaF-TiO2 and B/NaF-TiO2SiPc were 3.10 and 2.90 eV respectively, lower than pure TiO2 (3.17 eV). The photocatalytic activity of the synthesized materials was tested using carbamazepine (CBZ) as the model substrate. Carbamazepine removal after 4 h of irradiation was almost 100% for B/NaF-TiO2 and 70% for B/NaF-TiO2SiPc; however, the substrate mineralization proceeded slower, suggesting the presence of organic intermediates after the complete disappearance of the pollutant. Full article
Show Figures

Graphical abstract

Article
Comparison of Thermal and Flow-Based Modulation in Comprehensive Two-Dimensional Gas Chromatography—Time-of-Flight Mass Spectrometry (GC × GC-TOFMS) for the Analysis of Base Oils
Separations 2020, 7(4), 70; https://doi.org/10.3390/separations7040070 - 04 Dec 2020
Cited by 1 | Viewed by 922
Abstract
Base oils are produced by refining crude oil or through chemical synthesis. They are a key component of engine oils. With an immense range of carbon numbers and boiling points, analyzing such complex mixtures is very difficult. The need to monitor industrial petroleum [...] Read more.
Base oils are produced by refining crude oil or through chemical synthesis. They are a key component of engine oils. With an immense range of carbon numbers and boiling points, analyzing such complex mixtures is very difficult. The need to monitor industrial petroleum processing steps, as well as to identify petrochemical environmental pollutants, drives the search for improved characterization methods. Comprehensive two-dimensional gas chromatography (GC × GC) is one of the best tools for that. The modulator used in GC × GC is responsible for trapping/sampling the first dimension (1D) column analytes, then reinjecting them in the form of narrow bands onto the second dimension (2D) column for further separation. Modulators used today generally fall into two categories, thermal and flow ones. Heater-based thermal modulators trap the 1D column effluent at or above ambient temperatures. Flow-based modulators utilize storage loop(s) to collect the 1D effluent, which is subsequently flushed into the second-dimension column for further separation. A single-stage, consumable-free thermal modulator and a reverse fill/flush flow modulator were compared for the characterization of base oils. Both were evaluated on their ability to achieve separation of several conventional and synthetic engine oils components. A reverse column set, polar 1D and nonpolar 2D, allowed group-type analysis of all classes, including linear, branched, and aromatic species. The results show the ability to achieve a comprehensive separation of specific compound classes and the differentiation of engine oil types and manufacturers. Soft ionization assisted in tentative identification of two alkylated diphenylamines in each sample. The advantages and limitations of both thermal and flow modulation are presented. Full article
Show Figures

Figure 1

Review
Recent Advances in Molecularly Imprinted Membranes for Sample Treatment and Separation
Separations 2020, 7(4), 69; https://doi.org/10.3390/separations7040069 - 30 Nov 2020
Cited by 9 | Viewed by 1118
Abstract
This review describes the recent advances from the past five years concerning the development and applications of molecularly imprinted membranes (MIMs) in the field of sample treatment and separation processes. After a short introduction, where the importance of these materials is highlighted, a [...] Read more.
This review describes the recent advances from the past five years concerning the development and applications of molecularly imprinted membranes (MIMs) in the field of sample treatment and separation processes. After a short introduction, where the importance of these materials is highlighted, a description of key aspects of membrane separation followed by the strategies of preparation of these materials is described. The review continues with several analytical applications of these MIMs for sample preparation as well as for separation purposes covering pharmaceutical, food, and environmental areas. Finally, a discussion focused on possible future directions of these materials in extraction and separation field is also given. Full article
(This article belongs to the Special Issue Novel Sample Preparation Techniques)
Show Figures

Graphical abstract

Article
Separation of Benzene/Cyclohexane Mixtures by Pervaporation Using Poly (Ethylene-Co-Vinylalcohol) and Carbon Nanotube-Filled Poly (Vinyl Alcohol-Co-Ethylene) Membranes
Separations 2020, 7(4), 68; https://doi.org/10.3390/separations7040068 - 30 Nov 2020
Cited by 4 | Viewed by 1166
Abstract
Poly(ethylene-co-vinylalcohol) (E-VOH) and carbon nanotube-filled poly (vinyl alcohol-co-ethylene) (E-VOH/CNT) were used as membranes to separate benzene/cyclohexane mixtures by pervaporation technique. To reach this goal, E-VOH and E-VOH/CNT membranes were prepared by solvent casting method and characterized by differential scanning calorimetry (DSC), thermogravimetry analysis [...] Read more.
Poly(ethylene-co-vinylalcohol) (E-VOH) and carbon nanotube-filled poly (vinyl alcohol-co-ethylene) (E-VOH/CNT) were used as membranes to separate benzene/cyclohexane mixtures by pervaporation technique. To reach this goal, E-VOH and E-VOH/CNT membranes were prepared by solvent casting method and characterized by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The swelling tests were used to study the mass transfer of the benzene/cyclohexane mixture and their pure components. The separation by pervaporation process was carried out at 25 °C in which the effect of CNTs incorporated into E-VOH matrix and the initial concentration of benzene in the feed on the permeate flux, j, and separation factor, β, performance was investigated. The results obtained were very promising, in which the integration of CNTs through E-VOH chains increased the absorption area and raised the flux to 740 g/m2∙h. The separation factor increased to 9.03 and the pervaporation separation reached an index of 5942.2 g/m2∙h for the azeotropic mixture during 3 h of the separation process. In contrast, for the unfilled E-VOH membrane, it was found that these parameters were a rise of 280 g∙m−2∙h−1, separation factor of 12.90 and pervaporation separation index of 3332.0 g/m2∙h, under the same conditions. Likewise, the calculation of the performance of the E-VOH/CNT membrane with regard to that of the unfilled membrane indicated 2.64 for the total flux and 0.70 for the separation factor. It was also revealed that the best compromise of the filled membrane in terms of total cumulative flux and separation factor is obtained for the feed containing the azeotropic mixture. Full article
Show Figures

Figure 1

Article
Bioethanol Production from Date Seed Cellulosic Fraction Using Saccharomyces cerevisiae
Separations 2020, 7(4), 67; https://doi.org/10.3390/separations7040067 - 26 Nov 2020
Cited by 4 | Viewed by 1291
Abstract
This study investigates the feasibility of producing ethanol from date palm seeds. The chemical compositions of three varieties of date seeds were first studied, showing mainly the presence of cellulose and hemicellulose. Ethanol was produced after a pre-treatment of date seeds using acid [...] Read more.
This study investigates the feasibility of producing ethanol from date palm seeds. The chemical compositions of three varieties of date seeds were first studied, showing mainly the presence of cellulose and hemicellulose. Ethanol was produced after a pre-treatment of date seeds using acid hydrolysis to extract the cellulosic fraction and to remove the lignin. Producing ethanol by fermentation was performed using the yeast Saccharomyces cerevisiae for 24 h, during which ethanol yield, biomass concentration, and total reducing sugars were recorded. The results obtained showed that the sugar content decreased over time, while ethanol production increased. Indeed, date seeds gave the highest ethanol concentration of 21.57 g/L after 6 h of alcoholic fermentation. These findings proved the feasibility of producing ethanol from date seeds. Full article
Show Figures

Figure 1

Article
Development and Application of an ICP-AES Method for the Determination of Nutrient and Toxic Elements in Savory Snack Products after Autoclave Dissolution
Separations 2020, 7(4), 66; https://doi.org/10.3390/separations7040066 - 26 Nov 2020
Cited by 3 | Viewed by 907
Abstract
In this study, a method for the determination of trace elements in snacks using inductively coupled plasma–atomic emission spectrometry (ICP-AES) is presented. The examined elements were Pb, Ni, Cr, Cu, Mg, Zn, Fe, Al, Ba, Ca, Co, Mn and Cd. Under the optimized [...] Read more.
In this study, a method for the determination of trace elements in snacks using inductively coupled plasma–atomic emission spectrometry (ICP-AES) is presented. The examined elements were Pb, Ni, Cr, Cu, Mg, Zn, Fe, Al, Ba, Ca, Co, Mn and Cd. Under the optimized conditions, digestion of 300 mg of the snack samples was performed by the addition of 5 mL of nitric acid in a Teflon autoclave and by heating the obtained mixture at 120 °C for 75 min. In order to evaluate the efficiency of the proposed protocol, method linearity, accuracy precision, limits of detection (LODs) and limits of quantification (LOQs) were evaluated. The relative standard deviations (RSD%) for all elements were lower than 13.5%, demonstrating that the method offered good precision. The relative recoveries values (R%) ranged between 80–120%, demonstrating that the method offered good accuracy. The LODs for all the trace elements ranged between 0.18 and 3.75 μg g−1, while the LOQs ranged between 0.60 and 12.50 μg g−1. Finally, the proposed protocol was implemented for the analysis of a wide variety of savory snack samples including commercial snacks from corn, potato chips, popcorns, puffed rice cake and crackers. Full article
(This article belongs to the Special Issue Advances in Food and Biological Samples Analysis)
Article
The Influence of Mycorrhizal Fungi on the Accumulation of Sennosides A and B in Senna alexandrina and Senna italica
Separations 2020, 7(4), 65; https://doi.org/10.3390/separations7040065 - 25 Nov 2020
Cited by 1 | Viewed by 1001
Abstract
Symbiotic arbuscular mycorrhizal fungi (AMF) play a major role in plant development, growth, and relationships with the environment through a change in the accumulation of secondary metabolites; hence, we planned to investigate AMF’s influence on sennoside A and B accumulation in Senna alexandrina [...] Read more.
Symbiotic arbuscular mycorrhizal fungi (AMF) play a major role in plant development, growth, and relationships with the environment through a change in the accumulation of secondary metabolites; hence, we planned to investigate AMF’s influence on sennoside A and B accumulation in Senna alexandrina (SA) and Senna italica (SI). Seeds of SA (S. alexandrina free of mycorrhizae) and SI (S. italica free of mycorrhizae) were planted in two types of soils: +mycorrhiza and—mycorrhiza. The plant leaves of SA, SI, S. alexandrina with mycorrhizae (SAM) and S. italica with mycorrhizae (SIM) were collected and extracted (with 85% methanol), and sennoside A and B content was evaluated by the HPLC–UV method. The antioxidant activity of SA, SI, SAM and SIM was evaluated by using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods, while antimicrobial properties were evaluated by the minimum inhibitory concentration method (MIC). The AMF colonization was 85.66% and 85%, respectively, in the roots of SA and SI. The HPLC analysis showed a significant increase in (%) the content of sennoside A/sennoside B by 71.11/88.21, respectively, in SAM and 6.76/36.37 in SIM, which clearly indicated positive AMF effects. The DPPH/ABTS [The half maximal inhibitory concentration (IC50): 235.9/321.5 µg/mL] scavenging activity of SAM was comparatively higher and it also exhibited strong antibacterial action (MIC: 156.25 µg/mL), which supported the increase in sennoside content. This finding may be useful for further investigations of the symbiotic relation of mycorrhizal fungi with other plant species. Full article
Show Figures

Figure 1

Article
Detection of Microbial Nitroreductase Activity by Monitoring Exogenous Volatile Organic Compound Production Using HS-SPME-GC-MS
Separations 2020, 7(4), 64; https://doi.org/10.3390/separations7040064 - 19 Nov 2020
Cited by 1 | Viewed by 967
Abstract
Development of a rapid approach for universal microbial detection is required in the healthcare, food and environmental sectors to aid with medical intervention, food safety and environmental protection. This research investigates the use of enzymatic hydrolysis of a substrate by a microorganism to [...] Read more.
Development of a rapid approach for universal microbial detection is required in the healthcare, food and environmental sectors to aid with medical intervention, food safety and environmental protection. This research investigates the use of enzymatic hydrolysis of a substrate by a microorganism to generate a volatile organic compound (VOC). One such enzyme activity that can be used in this context is nitroreductase as such activity is prevalent across a range of microorganisms. A study was developed to evaluate a panel of 51 microorganisms of clinical interest for their nitroreductase activity. Two enzyme substrates, nitrobenzene and 1-fluoro-2-nitrobenzene, were evaluated for this purpose with evolution, after incubation, of the VOCs aniline and 2-fluoroaniline, respectively. Detection of the VOCs was done using headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) with obtained limits of quantitation (LOQ) of 0.17 and 0.03 µg/mL for aniline and 2-fluoroaniline, respectively. The results indicated that both enzyme substrates were reduced by the same 84.3% of microorganisms producing the corresponding volatile anilines which were detected using HS-SPME-GC-MS. It was found that nitroreductase activity could be detected after 6–8 h of incubation for the selected pathogenic bacteria investigated. This approach shows promise as a rapid universal microbial detection system. Full article
Show Figures

Graphical abstract

Article
Screening Carpet Substrate Interferences in Arson Identification by Solid Phase Microextraction and Gas Chromatography-Mass Spectrometry
Separations 2020, 7(4), 63; https://doi.org/10.3390/separations7040063 - 19 Nov 2020
Viewed by 1057
Abstract
The sample analysis and data interpretation is the most challenging step of fire debris analysis, due to the presence of combustion and pyrolysis products in the substrate material. In this study, a headspace solid phase microextraction (HS-SPME) procedure was applied to the extraction [...] Read more.
The sample analysis and data interpretation is the most challenging step of fire debris analysis, due to the presence of combustion and pyrolysis products in the substrate material. In this study, a headspace solid phase microextraction (HS-SPME) procedure was applied to the extraction of combustion and pyrolysis products from three commonly used carpet substrate materials, made of nylon 6,6 and polyesters. Each carpet sample was burned with and without two different ignitable liquids (ILs), i.e., gasoline and kerosene, and the Total Ion Chromatograms (TICs) and Extracted Ion Profiles of characteristic class compounds of ILs were obtained and compared to those of unburned neat ILs, using gas-chromatography mass spectrometry (GC-MS), to study the possible interferences of these substrate materials in fire debris analysis. Full article
(This article belongs to the Special Issue Microextraction Techniques for Sample Preparation)
Show Figures

Figure 1

Communication
Development of an UPLC-MS/MS Method for Quantitative Analysis of Clotrimazole in Human Plasma Samples
Separations 2020, 7(4), 62; https://doi.org/10.3390/separations7040062 - 16 Nov 2020
Viewed by 860
Abstract
An ultra-performance liquid chromatography-tandem mass spectrometry method was developed for the quantification of clotrimazole (CTZ) plasma levels after intravaginal administration of the drug given at approved dosages. Plasma samples were extracted by liquid–liquid extraction and a single chromatographic run could be completed within [...] Read more.
An ultra-performance liquid chromatography-tandem mass spectrometry method was developed for the quantification of clotrimazole (CTZ) plasma levels after intravaginal administration of the drug given at approved dosages. Plasma samples were extracted by liquid–liquid extraction and a single chromatographic run could be completed within about 2 min. The method was linear over the investigated range (0.488–250 ng/mL) with all the correlation coefficients, R2, greater than 0.9903. All data were in the range of ±15.0% with respect to the nominal concentration for high QC and medium QC, and in the range ±20% with respect to the nominal concentration for low QC. This rapid and sensitive method was validated and could be applied to human plasma samples from a healthy volunteer, showing that the assay is able to detect plasma concentrations of CTZ in the range of those found after the administration of the drug at approved dosages in the clinical setting. Full article
Show Figures

Figure 1

Article
Quantitative Explanation of Basic Compound Retention Mechanisms in Reversed-Phase Mode Liquid Chromatography
Separations 2020, 7(4), 61; https://doi.org/10.3390/separations7040061 - 30 Oct 2020
Viewed by 784
Abstract
The quantitative analysis of the chromatographic behavior of basic compounds measured with pentyl-, hexenyl-, and octyl-bonded silica gels were analyzed in silico employing model phases. The main retention force was the van der Waals (VW) interaction, and the main desorption force was an [...] Read more.
The quantitative analysis of the chromatographic behavior of basic compounds measured with pentyl-, hexenyl-, and octyl-bonded silica gels were analyzed in silico employing model phases. The main retention force was the van der Waals (VW) interaction, and the main desorption force was an electrostatic (ES) interaction. The contribution of hydrogen bonding (HB) was weak compared to that for acidic compounds. The quantitative explanation was achieved utilizing the calculated VW, HB, and ES energy values obtained from a molecular mechanics program. The electron localization was observed at the molecular interaction-site calculated MOPAC program. This fundamental approach was like that of explaining chemical reactions. The difference was electron localization in chromatography or electron transfer in a chemical reaction. Full article
Show Figures

Figure 1

Article
A Simple, Fast, and Green Oil Sample Preparation Method for Determination of Cannabidioloic Acid and Cannabidiol by HPLC-DAD
Separations 2020, 7(4), 60; https://doi.org/10.3390/separations7040060 - 29 Oct 2020
Cited by 3 | Viewed by 1362
Abstract
Currently, the medical use of food supplements containing Cannabis sativa has attracted the interest of consumers, as well as the medical and scientific community. With the increasing consumption of these products, there is also a risk of their abuse or discrepancy between the [...] Read more.
Currently, the medical use of food supplements containing Cannabis sativa has attracted the interest of consumers, as well as the medical and scientific community. With the increasing consumption of these products, there is also a risk of their abuse or discrepancy between the actual and declared contents of active substances by the manufacturer in these products. Thus, the development and elaboration of analytical procedures for determination of appropriate phytocannabinoids seems to be important. This work focuses on the development of a simple, fast and environmentally friendly liquid-liquid extraction method combined with fat freezing from an oil sample to isolate two phytocannabinoids: cannabidiol (CBD) and cannabidiolic acid (CBDA). The extraction method was optimized considering efficacy and repeatability of extraction, as well as minimalizing use of organic reagents and sample amount. Under the optimized conditions, extraction recovery for CBD was 97.3–109% and for CBDA was 69.1–69.5% with precision (RSD, %) 5.0–8.4 and 7.1–10.6, respectively. The evaluated main analytical parameters of the developed high pressure liquid chromatography with diode array detector (HPLC-DAD) method for both studied cannabinoids are satisfactory. The usability of the developed method was checked by analysis of real samples of a food supplement–hemp oil enriched with CBD. Full article
(This article belongs to the Special Issue Microextraction Techniques for Sample Preparation)
Show Figures

Figure 1

Article
Development and Validation of Rapid RP-HPLC and Green Second-Derivative UV Spectroscopic Methods for Simultaneous Quantification of Metformin and Remogliflozin in Formulation Using Experimental Design
Separations 2020, 7(4), 59; https://doi.org/10.3390/separations7040059 - 29 Oct 2020
Cited by 11 | Viewed by 2032
Abstract
Recently, a new formulation containing metformin HCl (MFH) and remogliflozin etabonate (RGE) has been approved for the management of diabetes mellitus. However, only one analytical method has been reported for the simultaneous determination of both the analytes. Therefore, the current study was designed [...] Read more.
Recently, a new formulation containing metformin HCl (MFH) and remogliflozin etabonate (RGE) has been approved for the management of diabetes mellitus. However, only one analytical method has been reported for the simultaneous determination of both the analytes. Therefore, the current study was designed to develop simple UV derivative spectroscopic and rapid RP-HPLC methods for simultaneous determination of MFH and RGE. The chromatographic separation of MFH and RGE was performed using a monolithic C18 column with an optimized chromatographic conditions carried out by full factorial Box–Behnken design model. The spectroscopic technique was based on the determination of peak amplitude of second-order derivative UV spectra at zero crossings. Further, both the methods were validated and compared statistically using Student’s-t-test and F-test, and employed for the concurrent estimation of MFH and RGE in laboratory mixed solutions and formulations. Perturbation plots and response surface models showed the effect of chromatographic parameters and the final chromatographic condition was selected from 47 solutions suggested by the desirability function. Further, UV spectroscopic and HPLC procedures showed good linearity in the range of 1–24 µg/mL and 2–150 µg/mL for RGE and 2–30 µg/mL and 5–200 µg/mL for MFH, respectively. The average percent assay was found to be 99.51% and 99.80% for MFH and 99.60% and 100.07% for RGE by spectroscopic and HPLC methods, respectively. The proposed methods were simple, accurate, precise, and rapid. Therefore, they can be used for regular quality control of MFH and RGE formulations and dissolution studies as well. Full article
Show Figures

Figure 1

Article
Improved Renoprotection in Diabetes with Combination Therapy of Coccinia indica Leaf Extract and Low-Dose Pioglitazone
Separations 2020, 7(4), 58; https://doi.org/10.3390/separations7040058 - 26 Oct 2020
Cited by 2 | Viewed by 1121
Abstract
Background: The metabolic changes associated with diabetes can lead to nephropathy eventually resulting in end-stage renal disease. Current antidiabetic therapies do not effectively prevent the onset of diabetic kidney diseases as well as progression. Aim: To evaluate the effect of Coccinia indica leaf [...] Read more.
Background: The metabolic changes associated with diabetes can lead to nephropathy eventually resulting in end-stage renal disease. Current antidiabetic therapies do not effectively prevent the onset of diabetic kidney diseases as well as progression. Aim: To evaluate the effect of Coccinia indica leaf extract alone and in combination with pioglitazone, an antihyperglycemic agent was used to modulate the progressive kidney damage induced by type 2 diabetes in rats. Hypotheses: Pioglitazone causes severe adverse effects when administered for long-term therapy. The hypotheses in this study is to examine the renoprotective effect of Coccinia indica leaf extract (200 mg/kg p.o.) when co-administered with low-dose pioglitazone (7 mg/kg) in type-2-diabetes-induced nephropathy in rats and simultaneously evaluate the hypoglycemic response as well. Methods: Rats (Males, Sprague Dawley) were kept on a high-fat diet and were given a single dose of streptozotocin (35 mg/kg, i.p.) to induce diabetic nephropathy. Treatment groups received either Coccinia indica leaf extract or pioglitazone or pioglitazone with Coccinia indica extract, fenofibrate, or lisinopril for 7 weeks. Blood glucose, antioxidant status, triglycerides, total cholesterol, creatinine, blood urea nitrogen, and proteinuria levels were estimated and compared with the normal control and disease control (untreated) groups. Results: The untreated diabetic rats showed increased blood glucose levels, lipid profiles, and renal oxidative stress, along with an increase in nephropathy markers such as blood urea nitrogen, creatinine, and proteinuria. Histopathological examination revealed glomerular damage. Combination treatment with Coccinia indica leaf extract and a low dose of pioglitazone normalized the nephropathic markers as well as histopathological changes. Conclusion: Coccinia indica leaf extract when co-administered with a low dose of pioglitazone as antidiabetic therapy showed good glycemic control and a beneficial renoprotective effect. Combination therapy would lower the dose of pioglitazone and also protect kidneys from drug-induced toxicity as observed from normalized nephropathic markers in a diabetic rat model. Full article
(This article belongs to the Special Issue Extraction and Isolation of Natural Products)
Show Figures

Figure 1

Article
Long-Chain Base (LCB)-Targeted Lipidomics Study Uncovering the Presence of a Variety of LCBs in Mammalian Blood
Separations 2020, 7(4), 57; https://doi.org/10.3390/separations7040057 - 23 Oct 2020
Viewed by 1028
Abstract
Globotriaosylsphingosine (LysoGb3) is a biomarker for Fabry disease (OMIM 301500) that contains long-chain bases (LCBs) as a building block. There have been several studies proposing that LysoGb3 forms with distinct LCBs could be putative disease subtype-related biomarkers for this congenital [...] Read more.
Globotriaosylsphingosine (LysoGb3) is a biomarker for Fabry disease (OMIM 301500) that contains long-chain bases (LCBs) as a building block. There have been several studies proposing that LysoGb3 forms with distinct LCBs could be putative disease subtype-related biomarkers for this congenital disorder; however, there have been no detailed multiple reaction monitoring-based studies examining the LCB distribution in this lysosphingolipid. To achieve this, we established an assay procedure that aimed at elucidating the LCB-targeted lipidome using liquid chromatography–tandem mass spectrometry. Consistent with previous studies, we found d18:1 to be the major LCB species of the LysoGb3 in pooled human plasma, while some atypical LCBs, such as d18:2, d18:0, t18:1, d16:1, and d17:1, were detected as minor fractions. When the same methodology was applied to fetal bovine serum (FBS) as a positive control, we identified additional unique LCB species, such as t18:0, d20:1, t19:1, and t21:1, in herbivore LysoGb3. Furthermore, we found an elevation of sphingosine and LysoGb3, which are N-deacylated forms of ceramide and Gb3, respectively, in FBS, suggesting that ceramidase activity may be involved in this process. Thus, our LCB-targeted lipidomics data revealed that mammalian LCBs in glycosphingolipids have a greater variety of molecular species than previously expected. Full article
(This article belongs to the Special Issue Application of Chromatography in Biomolecular Chemistry)
Show Figures

Figure 1

Article
Biological Activity of Cannabis sativa L. Extracts Critically Depends on Solvent Polarity and Decarboxylation
Separations 2020, 7(4), 56; https://doi.org/10.3390/separations7040056 - 20 Oct 2020
Cited by 2 | Viewed by 1913
Abstract
Minor cannabinoid and non-cannabinoid molecules have been proposed to significantly contribute to the pharmacological profile of cannabis extracts. Phytoplant Research has developed highly productive cannabis cultivars with defined chemotypes, as well as proprietary methods for the extraction and purification of cannabinoids. Here, we [...] Read more.
Minor cannabinoid and non-cannabinoid molecules have been proposed to significantly contribute to the pharmacological profile of cannabis extracts. Phytoplant Research has developed highly productive cannabis cultivars with defined chemotypes, as well as proprietary methods for the extraction and purification of cannabinoids. Here, we investigate the effect of solvent selection and decarboxylation on the composition and pharmacological activity of cannabis extracts. A library of forty cannabis extracts was generated from ten different cannabis cultivars registered by Phytoplant Research at the EU Community Plant Variety Office. Plant material was extracted using two different solvents, ethanol and hexane, and crude extracts were subsequently decarboxylated or not. Cannabinoid content in the resulting extracts was quantified, and biological activity was screened in vitro at three molecular targets involved in hypoxia and inflammation (NF-κB, HIF-1α and STAT3). Changes in transcriptional activation were strongly associated to solvent selection and decarboxylation. Two decarboxylated extracts prepared with hexane were the most potent at inhibiting NF-κB transcription, while HIF-1α activation was preferentially inhibited by ethanolic extracts, and decarboxylated extracts were generally more potent at inhibiting STAT3 induction. Our results indicate that solvent selection and proper decarboxylation represent key aspects of the standardized production of cannabis extracts with reproducible pharmacological activity. Full article
Show Figures

Graphical abstract

Article
Enantiomeric Separation of Colchicine and Lacosamide by Nano-LC. Quantitative Analysis in Pharmaceutical Formulations
Separations 2020, 7(4), 55; https://doi.org/10.3390/separations7040055 - 16 Oct 2020
Cited by 4 | Viewed by 1198
Abstract
A chiral analytical methodology was developed by nano-liquid chromatography (nano-LC) enabling the enantiomeric separation of two chiral drugs, lacosamide (novel antiepileptic drug) and colchicine (antiuremic drug), commercialized as pure enantiomers. A capillary column lab-packed with an amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase was used [...] Read more.
A chiral analytical methodology was developed by nano-liquid chromatography (nano-LC) enabling the enantiomeric separation of two chiral drugs, lacosamide (novel antiepileptic drug) and colchicine (antiuremic drug), commercialized as pure enantiomers. A capillary column lab-packed with an amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase was used in a lab-assembled nano-LC system. Lacosamide and colchicine enantiomers were separated in less than 8.0 and 9.0 min, respectively, with resolution values of 1.6 and 2.3, using 20 nL of sample and 1.8 µL of mobile phase per analysis. The analytical characteristics of the proposed methodology were evaluated according to the International Council for Harmonisation (ICH) guidelines, showing good analytical performance with good recoveries (97–98% and 100–103%) and precision values (relative standard deviation (RSD) <10.5 and <3.0%) for lacosamide and colchicine enantiomers, respectively. LODs were 1.7 and 2.0 µg/mL for (S)- and (R)-lacosamide, respectively, and 1.0 µg/mL for both colchicine enantiomers. Additionally, the developed methodology enabled to detect a 0.1% of the enantiomeric impurities, fulfilling the ICH regulation requirements. The method was applied to the determination of lacosamide and colchicine enantiomers in different pharmaceutical formulations to ensure their quality control. The content of the enantiomeric impurities was below a 0.1% and the amount of (R)-lacosamide and (S)-colchicine agreed with their labeled contents. Full article
(This article belongs to the Special Issue Enantiomeric Separations)
Show Figures

Graphical abstract

Article
LC-MS Phytochemical Screening, In Vitro Antioxidant, Antimicrobial and Anticancer Activity of Microalgae Nannochloropsis oculata Extract
Separations 2020, 7(4), 54; https://doi.org/10.3390/separations7040054 - 08 Oct 2020
Cited by 11 | Viewed by 1947
Abstract
Nowadays, marine microalgae are recognized to be a considerably novel and rich origin of bioactive moieties utilized in the sectors of nutraceuticals and pharmaceuticals. In the present study, Nannochloropsis oculata extract (AME) was associated with a wide variety of pharmacological studies such as [...] Read more.
Nowadays, marine microalgae are recognized to be a considerably novel and rich origin of bioactive moieties utilized in the sectors of nutraceuticals and pharmaceuticals. In the present study, Nannochloropsis oculata extract (AME) was associated with a wide variety of pharmacological studies such as in vitro antioxidant, antibacterial, and antifungal and anticancer activity (MDA-MB-231) in cancer cells through in vitro models. In the study, the chemical composition and structure of the bioactive compounds found in the AME extract were studied using the LC-MS technique. The results of the anticancer activity showed a decrease in the percentage of cell viability of the MDA-MB-231 cells in a concentration- and time-dependent manner (400 μg/mL at 24 h, 300 μg/mL at 48 h, and 200 μg/mL at 72 h). We have also observed morphological changes in the cells that could be associated with treatment with AME extract. Our observation of the AME extract-treated MDA-MB231 cells under light microscopy showed that when the concentration increased, the number of cells began to decrease. As far as LC-MS analysis is concerned, it showed the presence of the bioactive molecules was terpenoids along with carotenoids, polyphenolic and fatty acids. The result revealed that the AME extract exhibited noteworthy in vitro free radical scavenging potential, with an IC50 value of 52.10 ± 0.85 µg/L in DPPH assay, 122.84 ± 2.32 µg/mL in H2O2 assay and, 96.95 ± 1.68 µg/mL in ABTS assay. The activity was found to be highly significant against bacteria (Gram-positive and negative) and moderately significant against fungal strain with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) values between 15.63 and 500 µg/mL. Full article
Show Figures

Figure 1

Article
Determination of Synthetic Cathinones in Urine and Oral Fluid by Liquid Chromatography High-Resolution Mass Spectrometry and Low-Resolution Mass Spectrometry: A Method Comparison
Separations 2020, 7(4), 53; https://doi.org/10.3390/separations7040053 - 02 Oct 2020
Cited by 1 | Viewed by 1293
Abstract
Synthetic cathinones have become very popular recreational drugs. Therefore, determining them in biological samples is now a matter of concern. In recent years, different methods that have been developed can determine these drugs at low-concentration levels. In general, liquid chromatography mass spectrometry detection [...] Read more.
Synthetic cathinones have become very popular recreational drugs. Therefore, determining them in biological samples is now a matter of concern. In recent years, different methods that have been developed can determine these drugs at low-concentration levels. In general, liquid chromatography mass spectrometry detection plays an important role in these methods and the trend is to use low-resolution and high-resolution mass spectrometry. In this article, for the first time, we compare these two analyzers using an Orbitrap and a triple quadrupole mass spectrometer in order to determine a group of synthetic cathinones in urine and oral fluid samples. For this comparison, we evaluated and compared different parameters: Method detection and quantification limits, linearity, apparent recoveries, matrix effect, repeatability (intra-day), reproducibility (inter-day), and accuracy. Similar results were obtained for the two analyzers for the apparent recoveries and matrix effect. However, triple quadrupole showed higher sensitivity compared to Orbitrap for both urine and oral fluid samples. The quantification limits in urine and the detection limits in saliva were two times lower for triple quadrupole. Finally, when blind samples were analyzed to study the accuracy, similar results were obtained for both analyzers. Full article
Show Figures

Figure 1

Article
Development and Application of a Multi-Residue Method to Determine Pesticides in Agricultural Water Using QuEChERS Extraction and LC-MS/MS Analysis
Separations 2020, 7(4), 52; https://doi.org/10.3390/separations7040052 - 02 Oct 2020
Cited by 4 | Viewed by 1613
Abstract
Agricultural water is closely linked to surface and ground water as well as soil; hence, ensuring its safety is an important endeavor. We used the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) method to analyze multi-residue pesticides in agricultural water by using [...] Read more.
Agricultural water is closely linked to surface and ground water as well as soil; hence, ensuring its safety is an important endeavor. We used the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) method to analyze multi-residue pesticides in agricultural water by using a combined-sorbent-based clean-up procedure. Among the various sorbents examined, clean-up using ENVI-Carb combined with a primary secondary amine sorbent delivered the highest recovery of multi-residue pesticides (>93.9%). While the developed method showed satisfactory linearity (R2 > 0.9991), precision, and specificity, recovery was low for pyrazolate (29.1%) and thidiazuron (59.2%). The limits of detection and quantification for the 55 pesticides targeted in this study were in 0.02–3.0 μg L−1 and 0.1–9.9 μg L−1, respectively. The developed method was used to identify and quantify multi-residue pesticides during sample analysis. The results suggest that the QuEChERS method employing a combination of ENVI-Carb and another sorbent can be applied for the effective analysis of multi-residue pesticides in agricultural water. Full article
(This article belongs to the Special Issue Analysis of Organic Micropollutants)
Show Figures

Graphical abstract

Article
Determination of Trans-Anethole in Essential Oil, Methanolic Extract and Commercial Formulations of Foeniculum vulgare Mill Using a Green RP-HPTLC-Densitometry Method
Separations 2020, 7(4), 51; https://doi.org/10.3390/separations7040051 - 29 Sep 2020
Cited by 1 | Viewed by 1217
Abstract
Due to the lack of ecofriendly/green reversed-phase high-performance thin-layer chromatography (RP-HPTLC) methods for trans-anethole (TAL) and its simplicity over routine analytical techniques, there was a necessity to establish a suitable HPTLC methodology for the quantitative analysis of TAL. Therefore, the first objective of [...] Read more.
Due to the lack of ecofriendly/green reversed-phase high-performance thin-layer chromatography (RP-HPTLC) methods for trans-anethole (TAL) and its simplicity over routine analytical techniques, there was a necessity to establish a suitable HPTLC methodology for the quantitative analysis of TAL. Therefore, the first objective of this research was to develop an accurate, rapid and green RP-HPTLC densitometry methodology for the quantitative analysis of TAL in essential oil, traditional and ultrasound-assisted extracts of Foeniculum vulgare Mill and commercial formulations. The second objective was to compare the traditional method of extraction of TAL with its ultrasound-assisted method of extraction. The chromatogram of TAL from essential oil and traditional and ultrasound-assisted extracts of fennel and commercial formulations was verified by recoding its single spectra at Rf = 0.31 ± 0.01 in comparison to standard TAL. The proposed analytical methodology has been found to be superior in terms of linearity, accuracy and precision compared to most of the reported analytical methods for TAL analysis. The amount of TAL in the essential oil of fennel was recorded as 8.82 mg per g of oil. The content of TAL in traditional extracts of fennel, formulation 1 (dietary supplement 1) and formulation 2 (dietary supplement 2), was recorded as 6.44, 4.88 and 4.48 mg per g, respectively. The amount of TAL in ultrasound-assisted extracts of fennel, formulation 1 and formulation 2, was recorded as 8.34, 6.46 and 5.81 mg per g, respectively. The ultrasound method of extraction of TAL was found to be better than the traditional method of extraction. The results of validation studies and phytochemical analysis showed that the proposed methodology could be efficiently utilized for the quantification of TAL in the wide range of products having TAL as a component. Full article
(This article belongs to the Special Issue Current Trends in Chromatography for Bioanalytical Applications)
Show Figures

Figure 1

Article
Method Validation and Measurement Uncertainty Determination of Ethoxyquin and Antioxidant Activity in Paprika Seasonings and Paprika Sauces Frequently Consumed in South Korea
Separations 2020, 7(4), 50; https://doi.org/10.3390/separations7040050 - 28 Sep 2020
Cited by 1 | Viewed by 984
Abstract
In this study, we investigated and validated a method for the quantitative analysis of ethoxyquin in paprika seasonings and sauces, which are frequently consumed in South Korea. Using this analytical method, we were able to confirm the presence of ethoxyquin under optimized high-performance [...] Read more.
In this study, we investigated and validated a method for the quantitative analysis of ethoxyquin in paprika seasonings and sauces, which are frequently consumed in South Korea. Using this analytical method, we were able to confirm the presence of ethoxyquin under optimized high-performance liquid chromatography/photodiode array (HPLC-PDA) and liquid chromatography with tandem mass spectrometry conditions. Additionally, the antioxidant activity of ethoxyquin was assessed using the American Spice Trade Association values and its residual levels in paprika seasoning samples. The HPLC-PDA limits of detection and quantification for ethoxyquin were found to be 0.26 and 0.79 μg/mL, and 0.33 to 1.00 μg/mL, and the recoveries of ethoxyquin ranged from 86.75 to 101.70%, with relative standard deviations ranging from 0.31% to 3.59%. These results indicated that the analytical method in this study should be appropriate for the quantitative analysis of ethoxyquin in paprika seasoning and sauce matrices. Full article
(This article belongs to the Special Issue Development of Analytical Method in Food Science)
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop