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Separations
Volume 11
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Separations, Volume 11, Issue 1 (January 2024) – 36 articles

Cover Story (view full-size image): Extracting and profiling volatile metabolites from biological sample matrices reveals disease signatures, which is increasingly recognized as a frontier in disease diagnosis. Headspace solid-phase microextraction (HS-SPME) has been widely used to extract volatile compounds from biological samples, but its efficiency varies with different sample matrices. In this study, several HS-SPME parameters were optimized for lung lavage analysis. The new method produced a 340% increase in the total peak area and an 80% increase in peak number across various chemical classes. Our research demonstrates a significant enhancement in extraction performance and provides insights into how different compounds, affected by the matrix ionic strength, depend on their polarity. Overall, this optimization work paves the way for more precise and comprehensive volatile compound discovery using HS-SPME. View this paper
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16 pages, 4855 KiB  
Article
Solubility of Gallic Acid in Single and Mixed Solvents
by Yea-Rok Park and Bong-Seop Lee
Separations 2024, 11(1), 36; https://doi.org/10.3390/separations11010036 - 22 Jan 2024
Cited by 2 | Viewed by 3866
Abstract
Gallic acid, known for its biological activity contributing to human health, including antioxidant, anti-inflammatory, anticancer, and antimutagenic properties, was the focus of this study. The solubility of gallic acid was experimentally measured in pure and mixed solvents of water, ethanol, and acetic acid [...] Read more.
Gallic acid, known for its biological activity contributing to human health, including antioxidant, anti-inflammatory, anticancer, and antimutagenic properties, was the focus of this study. The solubility of gallic acid was experimentally measured in pure and mixed solvents of water, ethanol, and acetic acid and predicted using the COSMO-SAC model and the Hansen solubility parameter. The Hansen solubility parameter method predicted a higher solubility of gallic acid in pure water than in pure ethanol, and in a mixed solvent, it predicted the maximum solubility at 80% water content, showing different results from the experimental data trends. However, using the molar volume obtained from COSMO calculations resulted in a tendency that matched the experimental results. The results revealed higher solubility in ethanol compared to water, with the solubility in mixed solvent falling within the range between them. Using the same method, the Hansen solubility parameter obtained was applied to acetic acid/water and acetic acid/ethanol mixtures, and similar trends were observed compared to experimental data. In particular, gallic acid in the acetic acid/water mixture solvent exhibited maximum solubility, and this phenomenon was well-predicted. As the temperature increased, solubility in both pure and mixed solvents also increased. While the COSMO-SAC model effectively captured this trend, the predicted solubility values were slightly lower than the experimental data. The solubility trends depending on solvent types were confirmed by comparing the σ-profiles of each compound. The σ-profile of gallic acid closely resembled that of ethanol, and this result led to higher solubility than water and acetic acid. The maximum solubility in ethanol/water and acetic acid/water mixed solvents could be anticipated when two solvents with significant differences in their σ-profiles are mixed in an appropriate ratio. Full article
(This article belongs to the Special Issue Bioactive Compounds in Foods: Separation, Extraction and Application)
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26 pages, 395 KiB  
Review
Potential of Deep Eutectic Solvents in the Extraction of Organic Compounds from Food Industry By-Products and Agro-Industrial Waste
by Maja Molnar, Dajana Gašo-Sokač, Mario Komar, Martina Jakovljević Kovač and Valentina Bušić
Separations 2024, 11(1), 35; https://doi.org/10.3390/separations11010035 - 19 Jan 2024
Cited by 7 | Viewed by 3298
Abstract
Global food waste has a huge impact on the environment, as it is a source of greenhouse gas emissions and wasted natural resources. Across the world, over 30% of food is lost or wasted each year. Aside from this, the food industry, as [...] Read more.
Global food waste has a huge impact on the environment, as it is a source of greenhouse gas emissions and wasted natural resources. Across the world, over 30% of food is lost or wasted each year. Aside from this, the food industry, as well, is one of the biggest sources of agro-industrial waste and by-products, which can be valorized and used for different purposes. Such waste is a good source of bioactive organic compounds that can be extracted without altering their properties, where deep eutectic solvents can serve as green solvents and as an excellent replacement for volatile organic solvents. Isolated compounds can be used in innovative food production, chemical production, cosmetics and other industries. Deep eutectic solvents have attracted extraordinary attention due to their advantages such as environmental friendliness, availability and easy preparation, easy handling and utilization of non-toxic components for their formation. Due to these properties, they are a greener alternative to classic organic solvents for many processes, including extractions. In this paper, we review the utilization of deep eutectic solvents as potential green media for the extraction of organic compounds such as polyphenols, carbohydrates, proteins and alkaloids from by-products of the food industry and from agro-industrial waste. Full article
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12 pages, 2273 KiB  
Article
HPLC-MS/MS Analysis for Sphingosine 1-Phosphate after the Dephosphorylation by Hydrogen Fluoride
by Hee-Jung Kim, Seo-Hyeon Jung, Shokhid Gulyamov, Hyun-Gy Lee, Oybek Boyjigitov and Yong-Moon Lee
Separations 2024, 11(1), 34; https://doi.org/10.3390/separations11010034 - 18 Jan 2024
Viewed by 1987
Abstract
Sphingosine 1-phosphate (S1P) is a signaling lipid molecule involved in various cellular processes. It is important to develop a quantitative method for S1P to determine endogenous levels and to investigate its functions. As S1P is a tiny lipid component of most biological samples, [...] Read more.
Sphingosine 1-phosphate (S1P) is a signaling lipid molecule involved in various cellular processes. It is important to develop a quantitative method for S1P to determine endogenous levels and to investigate its functions. As S1P is a tiny lipid component of most biological samples, highly sensitive analysis by LC-MS/MS is required. The main challenge in S1P analysis by chromatography is peak-broadening due to the presence of a polar phosphate and the fact that S1P is indeed a zwitterion itself. In this study, we used hydrogen fluoride (HF) to efficiently remove a phosphate and then analyzed the surrogate, sphingosine, as a sharp peak by LC-ESI-MS/MS. We optimized the dephosphorylation reaction in terms of temperature and reaction time. Multiple reaction monitoring (MRM) for a dephosphorylated form of S1P and C17-S1P as an internal standard at m/z transition 300.4 > 282.4 (quantification ion), 300.4 > 262.4 (qualification ion), 286.3 > 268.2 (internal standard) was conducted. This method was validated by essential parameters such as specificity, linearity, range, LOQ, LOD, accuracy, precision, and repeatability. To confirm this new method, we quantified S1P levels in various serum products (100.0~284.4 nM). In the sample pretreatment conditions for extracting S1P, the concern about potential sphingosine contamination in serum was negligible. The dephosphorylation efficiency by this method was about two-fold higher than that of alkaline phosphatase (APase). To apply the method in vivo, we analyzed S1P in plasma and kidney tissues obtained from a chronic kidney disease (CKD) mouse model. S1P levels were increased only in CKD kidney tissue but not in plasma. In conclusion, by applying the dephosphorylation step with HF, we established a new, sensitive LC-MS/MS quantitative method for S1P that can be applied to biological samples. Full article
(This article belongs to the Topic Chromatography–Mass Spectrometry Analysis in Biomedical Research and Clinical Laboratory)
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19 pages, 4634 KiB  
Article
Theoretical Calculations and Experimental Investigation of Separation of Dy3+, Er3+, Tm3+ and Yb3+ by Cascade Extraction in TOGDA–Kerosene/Hydrochloric Acid System
by Yuzhen Bai, Aijun Gong, Lina Qiu, Yiwen Wang, Ge Gao, Weiyu Zhao, Yang Liu, Jiayi Yin, Xinyu Huang and Yiyang Chen
Separations 2024, 11(1), 33; https://doi.org/10.3390/separations11010033 - 17 Jan 2024
Cited by 2 | Viewed by 1626
Abstract
The hot spot extraction agent N,N,N′,N′-tetraoctyl-3-oxoglutaramide (TODGA) has the advantages of novelty, high efficiency and environmental protection in the separation of rare earths by tandem extraction. In this paper, the characteristic parameters for the separation of dysprosium, erbium, thulium and ytterbium ions [...] Read more.
The hot spot extraction agent N,N,N′,N′-tetraoctyl-3-oxoglutaramide (TODGA) has the advantages of novelty, high efficiency and environmental protection in the separation of rare earths by tandem extraction. In this paper, the characteristic parameters for the separation of dysprosium, erbium, thulium and ytterbium ions in the TOGDA–kerosene/hydrochloric acid system for tandem extraction were calculated. Using a 10% TODGA–kerosene/5 mol·L−1 hydrochloric acid extraction system, the mixture containing Dy3+ 0.258 mol·L−1, Er3+ 0.252 mol·L−1, Tm3+ 0.248 mol·L−1 and Yb3+ 0.242 mol·L−1 can be separated by three separation steps, and four products of Dy3+, Er3+, Tm3+ and Yb3+ can be obtained. The purity of the four products was 99.80%, 99.20%, 99.70% and 99.70%, and the yields were 99.03%, 98.97%, 97.88% and 96.98%, in order. In this paper, the reasons were analyzed for the differences in the ability of the TODGA system to extract heavy rare earth ions (REEs) in terms of density functionality, complex structure and bond valence model. These will provide more basic data and guidance for the industrial application of TODGA. Full article
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14 pages, 2306 KiB  
Article
HPLC/DAD Analysis and Antioxidant Activity of Adlay Sprouts and Seeds
by Gia-Han Tran, Neil-Patrick Uy, Shi-Heon Kang, Wonseok Heo, Eun-Song Lee, Seong-Soo Roh and Sanghyun Lee
Separations 2024, 11(1), 32; https://doi.org/10.3390/separations11010032 - 13 Jan 2024
Cited by 3 | Viewed by 2047
Abstract
Adlay is an annual plant known for its abundant bioactive compounds and diverse pharmacological activities. Coixol, a key component found in various parts of adlay, significantly contributes to its biological activity. This study was conducted to extract adlay sprouts and seeds using different [...] Read more.
Adlay is an annual plant known for its abundant bioactive compounds and diverse pharmacological activities. Coixol, a key component found in various parts of adlay, significantly contributes to its biological activity. This study was conducted to extract adlay sprouts and seeds using different solvents (methanol and ethanol) and extraction methods (reflux and ultrasonic extraction). The extracts were then evaluated for their total polyphenol and flavonoid contents, as well as antioxidant ability (DPPH and ABTS+). Additionally, the coixol content of these extracts was analyzed using HPLC/DAD analysis. The results showed that the extraction methods and solvents used impacted the bioactive compounds and their activities in the samples. Adlay sprouts exhibited a higher compound content and stronger antioxidant capacity than adlay seeds. Moreover, a substantial amount of coixol was found in the sprouts, while it was not detected in the seeds. This study emphasizes the importance of selecting appropriate extraction methods to optimize the biological activities of adlay sprouts and seeds. Adlay sprouts, with their enriched phytochemical compounds and enhanced antioxidant ability, could serve as a valuable material for health product applications. Full article
(This article belongs to the Special Issue HPLC or Other Chromatographic-Based Methods for Analysis of Bioactive Compounds in Plant, Food, and Pharmaceutical Products)
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13 pages, 6798 KiB  
Article
A Comparison of Volatile Organic Compounds in Puerariae Lobatae Radix and Puerariae Thomsonii Radix Using Gas Chromatography–Ion Migration Spectrometry
by Yingchao Mao, Lingfeng Zhu, Fuhua Fu, Lijun Zhu, Jiajing Chen, Jing Liu, Dan Huang and Chang Lei
Separations 2024, 11(1), 31; https://doi.org/10.3390/separations11010031 - 12 Jan 2024
Cited by 1 | Viewed by 1927
Abstract
Puerariae Radix is one of the most widely used ancient traditional Chinese medicines and is also consumed as food, which has rich edible and medicinal value. Puerariae Radix can be divided into Puerariae Lobatae Radix (PL) and Puerariae Thomsonii Radix (PT). These two [...] Read more.
Puerariae Radix is one of the most widely used ancient traditional Chinese medicines and is also consumed as food, which has rich edible and medicinal value. Puerariae Radix can be divided into Puerariae Lobatae Radix (PL) and Puerariae Thomsonii Radix (PT). These two medicinal materials are very similar, and they are often mixed up or misused. In this study, gas chromatography–ion migration spectrometry (GC-IMS) was used to analyze the volatile organic compounds (VOCs) of PL and PT, and the differences in VOCs were analyzed using fingerprint, principal component analysis (PCA), and orthogonal partial least squares discriminant analysis (OPLS-DA). The results showed that a total of 173 VOCs were obtained from PL and PT, and 149 were qualitatively identified, including 38 aldehydes, 22 alcohols, 22 ketones, 19 esters, 13 esters, 10 acids, 10 pyrazines, 6 terpenes, 4 furans, and 2 pyridines. The characteristic VOCs of PL and PT were clarified by constructing GC-IMS fingerprints. PL and PT can be effectively distinguished, and five characteristic VOCs were screened using PCA and OPLS-DA analysis methods. This study identified and evaluated the types and differences in VOCs in PL and PT. The established method is simple, rapid, accurate, and sensitive, and it provides theoretical guidance for the identification, tracing, and quality evaluation of PL and PT. Full article
(This article belongs to the Special Issue Design and Development of Sample Preparation Procedures for the Determination of Volatile Organic Compounds)
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22 pages, 5053 KiB  
Review
The Application of Liquid Chromatography for the Analysis of Organic UV Filters in Environmental and Marine Biota Matrices
by Maria Nieddu, Valeria Pasciu, Maria Piera Demontis and Elena Baralla
Separations 2024, 11(1), 30; https://doi.org/10.3390/separations11010030 - 12 Jan 2024
Cited by 2 | Viewed by 2187
Abstract
Sunscreens are topical preparations containing one or more compounds that protect humans from ultraviolet (UV) light. This review focuses on analytical methods, particularly liquid chromatography, with the aim of identifying and determining UV filters (UVFs) in environmental and marine biota matrices. A literature [...] Read more.
Sunscreens are topical preparations containing one or more compounds that protect humans from ultraviolet (UV) light. This review focuses on analytical methods, particularly liquid chromatography, with the aim of identifying and determining UV filters (UVFs) in environmental and marine biota matrices. A literature review was conducted using NIH (PubMed and Medline), FDA and EPA databases, Google Scholar, and federal regulations. This retrospective literature review is focused on the last five years. UVF quantification in environmental and biological matrices showed a wide array of methods where liquid chromatography is predominant. The scientific literature identified a large variety of analytical methodologies that are compared in this review to evaluate the better results in terms of limits of quantification and the possibility to identify as many analytes as possible simultaneously. Full article
(This article belongs to the Special Issue Application of Liquid Chromatography in Pharmaceutical and Toxicological Analysis)
17 pages, 4438 KiB  
Article
Preparation and Application of Si@Al Adsorbents for Different Pollutants Removal from Aqueous Solution
by Xiaoyu Xu, Jiahua Liu, Yuang Cao, Han Wang, Keqiang Zhang, Chein-Chi Chang and Suli Zhi
Separations 2024, 11(1), 29; https://doi.org/10.3390/separations11010029 - 12 Jan 2024
Viewed by 1619
Abstract
This study tried to use electroflocculating precipitated waste to prepare a Si@Al adsorbent by simply mixing sodium silicate at a mass ratio of 4:1 and calcining at 200 °C for 2 h. The adsorbent was low cost, high efficiency, and could remove a [...] Read more.
This study tried to use electroflocculating precipitated waste to prepare a Si@Al adsorbent by simply mixing sodium silicate at a mass ratio of 4:1 and calcining at 200 °C for 2 h. The adsorbent was low cost, high efficiency, and could remove a variety of contaminants (organic pollutants, antibiotics, and metal ions) from water. In this study, adsorbent characterization and pollutant adsorption experiments were carried out. The results showed that: Si@Al adsorbent had uniform particles, distinct layers, a loose porous appearance, and the internal structure was scattered without a crystal structure. The optimal adsorption conditions for tetracycline were as follows: dosage of adsorbent 2.0 g/L, reaction time 10 min, pH = 4.5, and tetracycline removal rate of 97.13%. The optimal adsorption conditions for MB (MB stands for methylene blue) were an adsorption dosage of 4.0 g/L, a reaction time of 15 min, pH = 4.5–8.5, and a removal rate of 96.39%. The optimal adsorption conditions for Cu were a 2.0 g/L dosage of adsorbent, a reaction time of 30 min, a pH of 8.5, and a highest removal rate of 97.47%. It was worth noting that the effect of temperature on TC, MB and Cu was not significant. At the same time, the kinetic fitting results showed that the adsorption of MB was more consistent with the quasi-second-order kinetic model, with R2 ranging from 0.9788 to 1.0000. The adsorption of TC and Cu was more consistent with the quasi-first-order kinetic model, with R2 ranging from 0.9598 to 0.9999 and 0.9844 to 0.9988, respectively. According to the results of thermodynamics, kinetics and zero potential point, the adsorption of tetracycline and methylene blue was mainly a physical adsorption, multilayer heterogeneous or single-layer homogeneous adsorption process. The adsorption of Cu was categorized as multi-layer heterogeneous chemical adsorption. The co-existing substances had little effect on the properties of the adsorbent, and the adsorbent could be recycled 5 times. Compared with other adsorbents, the results showed that the adsorbents had obvious advantages in terms of the raw material source, preparation method, time cost and removal effect. This study provided a “waste into treasure, green and efficient” multi-pollutant adsorption method. Full article
(This article belongs to the Special Issue Separation in Agricultural Waste Utilization)
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12 pages, 2517 KiB  
Article
The Dewatering Performance of a Compact Screw Press Manure Separator for Non-Typical Substrates
by Thomas Senfter, Igor Schweiggl, Manuel Berger, Christian Mayerl, Tobias Kofler, Michael Kraxner, Axel Steffens and Martin Pillei
Separations 2024, 11(1), 28; https://doi.org/10.3390/separations11010028 - 11 Jan 2024
Viewed by 2337
Abstract
The dewatering of substrates is one of the key tasks in the handling of material flows in a circular economy. Besides belt filters, sedimenters, and decanters, screw presses are frequently used to reduce the water content of substrates. However, screw presses available on [...] Read more.
The dewatering of substrates is one of the key tasks in the handling of material flows in a circular economy. Besides belt filters, sedimenters, and decanters, screw presses are frequently used to reduce the water content of substrates. However, screw presses available on the market are usually designed for high throughputs (>5 m3/h). The dewatering of smaller feed rates (<1 m3/h), however, requires more compact solutions. For this reason, a compact screw press (short screw length), which is normally used in agriculture for cow manure dewatering, was investigated in this work, as there exist no publications on this type of compact screw press. A mobile test setup was developed and loaded with different material such as digested sludge from a wastewater treatment plant, commercially available potting soil, wood shavings, and biological waste. The dry matter content of the feed material, the feed material itself, the screw rotational speed, and the weight setting (pressure) at the back plate were varied, and the effects on the dewatering result were recorded. A significant influence on the dewatering result was found for the weight setting, the type of substrate (particle size), and the dry substance content of the feed material. The tests confirmed that the compact screw press separator is suitable for the dewatering of wood shavings and biological waste (with an increase in dry matter percentage of up to 7.7%). The direct dewatering of potting soil and digested sludge is not possible and can only be implemented by using structural support material. This study fills the gap between published work on large screw presses and potentially new application fields of compact screw press manure separators, which, until now, have only been used in agriculture. Full article
(This article belongs to the Section Environmental Separations)
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15 pages, 2676 KiB  
Article
Headspace Solid-Phase Micro-Extraction Method Optimization and Evaluation for the Volatile Compound Extraction of Bronchoalveolar Lung Lavage Fluid Samples
by Antao Gao, Nina Nouri, Keisean Stevenson, Edith T. Zemanick, Jerry A. Nick and Jane E. Hill
Separations 2024, 11(1), 27; https://doi.org/10.3390/separations11010027 - 11 Jan 2024
Cited by 1 | Viewed by 2408
Abstract
Headspace solid-phase micro-extraction (HS-SPME) is a prevalent technique in metabolomics and volatolomics research. However, the performance of HS-SPME can vary considerably depending on the sample matrix. As a result, fine-tuning the parameters for each specific sample matrix is crucial to maximize extraction efficacy. [...] Read more.
Headspace solid-phase micro-extraction (HS-SPME) is a prevalent technique in metabolomics and volatolomics research. However, the performance of HS-SPME can vary considerably depending on the sample matrix. As a result, fine-tuning the parameters for each specific sample matrix is crucial to maximize extraction efficacy. In this context, we conducted comprehensive HS-SPME optimization for bronchoalveolar lavage fluid (BALF) samples using two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-ToFMS). Our exploration spanned several HS-SPME parameters, including vial size, dilution factor, extraction time, extraction temperature, and ionic strength. The 10 mL vial size, no sample dilution, extraction time of 50 min, extraction temperature of 45 °C, and 40% salt were identified as the optimized parameters. The optimized method was then evaluated by a pair-wise comparison of ten sets of samples. The results revealed that the optimized method yielded an increase of 340% in total peak area and an increase of 80% in total peak number. Moreover, enhancements were observed across nine major chemical classes in both peak area and number. Notably, the optimized method also doubled the number of volatile compounds consistently detected across BALF samples, from 52 to 108. Full article
(This article belongs to the Special Issue Feature Papers in Separations from Editorial Board Members)
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16 pages, 1510 KiB  
Review
Application and Development of Chemical Heat Washing Technology in Petroleum Oily Sludge Treatment: A Review
by Huapeng Liu, Xiyuan Wang, Youqian Zhai and Tingting Xu
Separations 2024, 11(1), 26; https://doi.org/10.3390/separations11010026 - 10 Jan 2024
Cited by 2 | Viewed by 2352
Abstract
Because of the requirements for accelerating the construction of a green, low-carbon, and recycling economy development system, the petrochemical industry has been paying attention to green and low-carbon transformations and innovations. Oily sludge is a type of bulk hazardous solid waste from various [...] Read more.
Because of the requirements for accelerating the construction of a green, low-carbon, and recycling economy development system, the petrochemical industry has been paying attention to green and low-carbon transformations and innovations. Oily sludge is a type of bulk hazardous solid waste from various sources that significantly harms the environment. Chemical heat washing of oily sludge represents a large proportion of the treatment technology for oily sludge, which can be used individually and has many applications in joint treatment with other processes. However, research on the formulation of cleaning agents for this process has mainly focused on the surfactant at this stage, and many studies have demonstrated the secondary pollution of surfactant; thus, research on reducing or replacing surfactants as cleaning agents has been conducted. This review highlights the research progress of chemical heat washing of oily sludge according to the classification of cleaning agents and describes the reasons for the stabilization of currently recognized oily sludge, the chemical heat washing process, and the mechanism of oil–soil separation. Finally, the research direction for new emulsions as new cleaning agents to replace surfactants is set out. Full article
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11 pages, 1399 KiB  
Article
Assessing the Conformity of Plasticizer-Free Polymers for Foodstuff Packaging Using Solid Phase Microextraction Coupled to Gas Chromatography/Mass Spectrometry
by Nicoletta De Vietro, Antonella Maria Aresta, Jennifer Gubitosa, Vito Rizzi and Carlo Zambonin
Separations 2024, 11(1), 25; https://doi.org/10.3390/separations11010025 - 9 Jan 2024
Cited by 2 | Viewed by 2111
Abstract
Phthalates are the synthetic chemical plasticizers with the most varied uses and are a source of concern due to their toxicity and ubiquity, so much so that even plasticizer-free polymers can contain them as non-intentionally added substances (NIAS). Food packaging is among the [...] Read more.
Phthalates are the synthetic chemical plasticizers with the most varied uses and are a source of concern due to their toxicity and ubiquity, so much so that even plasticizer-free polymers can contain them as non-intentionally added substances (NIAS). Food packaging is among the materials with the greatest impact. In this study, a simple protocol is proposed for the location and identification of dimethyl phthalate, diethyl phthalate, dipropyl phthalate, and dibutyl phthalate which is applicable to compliance studies of food packaging materials and for the associated risk assessment. Solid phase microextraction gas chromatography/mass spectrometry was used to evaluate the migration of four NIAS from food packaging to release media simulating food substrates. Three plasticizer-free polymers were used: two that were lab-made and based on sodium alginate and a commercial polyethylene film. Linearity ranged from the LOQ to 10 µg/mL; within-day and between-day precision values were between 12.3–25.7% and 21.9–35.8%, respectively; the LOD and LOQ were in the range 0.029–0.073 µg/mL and 0.122–0.970 µg/mL. Migration tests were conducted for different periods of time at room temperature and at 8 °C. Exposure to microwaves (MW) was also evaluated. All packaging materials tested had global migration limits lower than 10 mg/dm2 of material surface. Full article
(This article belongs to the Special Issue SPME Procedures for GC-MS Analysis of Foods Contaminants and/or Packaging Materials)
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16 pages, 4034 KiB  
Article
Tuning Nanopores in Tubular Ceramic Nanofiltration Membranes with Atmospheric-Pressure Atomic Layer Deposition: Prospects for Pressure-Based In-Line Monitoring of Pore Narrowing
by Michiel Nijboer, Asif Jan, Mingliang Chen, Kevin Batenburg, Julia Peper, Tom Aarnink, Fred Roozeboom, Alexey Kovalgin, Arian Nijmeijer and Mieke Luiten-Olieman
Separations 2024, 11(1), 24; https://doi.org/10.3390/separations11010024 - 9 Jan 2024
Cited by 1 | Viewed by 2498
Abstract
Atomic layer deposition (ALD) is known for its unparalleled control over layer thickness and 3D conformality and could be the future technique of choice to tailor the pore size of ceramic nanofiltration membranes. However, a major challenge in tuning and functionalizing a multichannel [...] Read more.
Atomic layer deposition (ALD) is known for its unparalleled control over layer thickness and 3D conformality and could be the future technique of choice to tailor the pore size of ceramic nanofiltration membranes. However, a major challenge in tuning and functionalizing a multichannel ceramic membrane is posed by its large internal pore volume, which needs to be evacuated during ALD cycling. This may require significant energy and processing time. This study presents a new reactor design, operating at atmospheric pressure, that is able to deposit thin layers in the pores of ceramic membranes. In this design, the reactor wall is formed by the industrial tubular ceramic membrane itself, and carrier gas flows are employed to transport the precursor and co-reactant vapors to the reactive surface groups present on the membrane surface. The layer growth for atmospheric-pressure ALD in this case proceeds similarly to that for state-of-the-art vacuum-based ALD. Moreover, for membrane preparation, this new reactor design has three advantages: (i) monolayers are deposited only at the outer pore mouths rather than in the entire bulk of the porous membrane substrate, resulting in reduced flow resistances for liquid permeation; (ii) an in-line gas permeation method was developed to follow the layer growth in the pores during the deposition process, allowing more precise control over the finished membrane; and (iii) expensive vacuum components and cleanroom environment are eliminated. This opens up a new avenue for ceramic membrane development with nano-scale precision using ALD at atmospheric pressure. Full article
(This article belongs to the Special Issue Research Progress in Nanomaterials and Processes for Separation Membranes)
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16 pages, 4757 KiB  
Article
Characterization, Antioxidant and Cytotoxic Evaluation of Demethoxycurcumin and Bisdemethoxycurcumin from Curcuma longa Cultivated in Costa Rica
by Andrea Mariela Araya-Sibaja, Felipe Vargas-Huertas, Silvia Quesada, Gabriela Azofeifa, José Roberto Vega-Baudrit and Mirtha Navarro-Hoyos
Separations 2024, 11(1), 23; https://doi.org/10.3390/separations11010023 - 8 Jan 2024
Viewed by 2434
Abstract
The biological activities of curcuminoids, the main polyphenol constituents of Curcuma longa (turmeric), have been the subject of many studies in recent years. However, these studies have focused on the major active compound, curcumin (CUR), while other important constituents, demethoxycurcumin (DMC) and bisdemethoxycurcumin [...] Read more.
The biological activities of curcuminoids, the main polyphenol constituents of Curcuma longa (turmeric), have been the subject of many studies in recent years. However, these studies have focused on the major active compound, curcumin (CUR), while other important constituents, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDM) have been less studied and reported in the literature regarding their bioactivity as well as their isolation and solid-state characterization. Hence, in this study, DMC and BDM were isolated using pressurized liquid extraction (PLE) followed by column chromatography and crystallization. HRMS and 1H and 13C NMR were used to characterize them. Solid-state characterization was performed through powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) techniques. Further, powder dissolution profiles were performed in two media, antioxidant and cytotoxic activities were determined through 2,2-diphenyl-1-picrylhidrazyl (DPPH) and an MTT assay on gastric adenocarcinoma (AGS), colorectal adenocarcinoma (SW-620), and hepatocellular carcinoma (HepG2) cell lines. DMC and BDM were extracted from Curcuma longa cultivated in Costa Rica, using pressurized liquid extraction (PLE), then isolated and purified, combining column chromatography and crystallization techniques. The highly pure solids obtained were shown to be crystalline with an amorphous component. Although the PXRD pattern of BDM suggested a high amorphous component, the crystal exhibited a well-defined and faceted shape. Meanwhile, DMC crystallized in a botryoidal habit, and this constitutes the first report for this compound. On the other hand, BDM was slightly more soluble than DMC, which in turn showed an antioxidant IC50 value 28% higher than BDM (12.46 and 17.94 µg/mL, respectively). In respect to the cytotoxic effects, DMC showed a better IC50 value than BDM for both the SW-620 and AGS cell lines, while BDM exhibited a better IC50 value than DMC against the HepG2 cell line (64.7 μM). In terms of selectivity, BDM and DMC had the highest SI value for SW-620 cells compared to non-tumoral cells, while both compounds also displayed the best cytotoxic effect against these colon adenocarcinoma SW-620 cells, indicating BDM and DMC as potential chemotherapeutic drugs. Full article
(This article belongs to the Special Issue Extraction, Isolation, and Purification of Natural Bioactive Compounds)
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11 pages, 2566 KiB  
Article
Prediction of Plate Height Curves of Porous-Shell Pillar Array Columns Micro-Pillar Array Columns
by Claudia Venditti, Gert Desmet and Alessandra Adrover
Separations 2024, 11(1), 22; https://doi.org/10.3390/separations11010022 - 6 Jan 2024
Cited by 1 | Viewed by 1648
Abstract
We investigate band broadening in the most widely adopted configuration of micro-pillar array columns (μPACs)—specifically, a cylindrical pillar array where both the pillar walls and the channel bottom are coated with a thin layer of mesoporous material. The two-zone moment analysis [...] Read more.
We investigate band broadening in the most widely adopted configuration of micro-pillar array columns (μPACs)—specifically, a cylindrical pillar array where both the pillar walls and the channel bottom are coated with a thin layer of mesoporous material. The two-zone moment analysis method is adopted to investigate the dispersion properties of μPACs in a broad range of shell thicknesses, reduced fluid velocities, and retention factors. Three different models of the unit cell, of increasing complexity, have been implemented, namely a two-dimensional model and two different three-dimensional models with and without the retentive bottom layer, the presence of which seems to have a very significant effect on the plate height curves. Model predictions are compared with experimental van Deemter curves for uncoated and coated porous layers, and a robust relationship between the intra-particle (porous-zone) diffusion coefficient Dpz and the retention factor k′ is established. Full article
(This article belongs to the Section Chromatographic Separations)
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14 pages, 3089 KiB  
Editorial
Central European Group for Separation Sciences (CEGSS)—Brief History and Memoirs on the Creation and Activity
by Bogusław Buszewski, Dušan Berek and Virginia Coman
Separations 2024, 11(1), 21; https://doi.org/10.3390/separations11010021 - 5 Jan 2024
Viewed by 1785
Abstract
The origin of the International Symposia on Separation Sciences (ISSS) can be found in the national gas chromatography scientific meetings held in Zagreb, Croatia, from 1967 and later at Plitvice Lakes until 1988 [...] Full article
(This article belongs to the Collection CEGSS Yesterday, Today and Tomorrow)
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13 pages, 2218 KiB  
Article
Effect of Fly Ash on the Mass Transfer Performance of CO2 Removal Using MEA and DEA Solutions in a Packed Tower
by Wenxia Xie, Chunmin Tu, Jun Zhang and Chengwei Xu
Separations 2024, 11(1), 20; https://doi.org/10.3390/separations11010020 - 5 Jan 2024
Viewed by 1694
Abstract
The accumulation of uncollected fly ash from flue gas in post-combustion CO2 capture processes is a significant concern in current coal-fired power plants due to its potential impact on the performance of CO2 absorbent and absorption towers. In order to determine [...] Read more.
The accumulation of uncollected fly ash from flue gas in post-combustion CO2 capture processes is a significant concern in current coal-fired power plants due to its potential impact on the performance of CO2 absorbent and absorption towers. In order to determine the effect of fly ash on the mass transfer performance of CO2 absorption into monoethanolamine (MEA) and diethanolamine (DEA) aqueous solutions, experimental studies were carried out using a small-sized packed tower equipped with θ-ring random packing. These studies were conducted under various operating parameters, including solution temperature, liquid/gas ratio (L/G), packing height, and fly ash concentration. The results show that the effect of fly ash on the outlet CO2 concentration was primarily observed during the initial stages of the experimental process. Moreover, the presence of fly ash leads to a reduction in the volumetric overall mass transfer coefficient (KGav) when using MEA and DEA solution, and increasing the fly ash concentration further exacerbates this negative impact. However, the effect of fly ash on the reduction in KGav is not significantly related to its chemical composition but rather depends on the operational parameters. With increasing solution temperature, liquid/gas ratio (L/G), and packing height, the KGav values for different solutions exhibit an upward trend. The negative effect of fly ash on KGav remains relatively stable for MEA as solution temperature and packing height increase. Compared to MEA, fly ash has a greater negative effect on DEA solution under the same experimental conditions. The analysis reveals that the detrimental effect of fly ash on KGav primarily stems from its ability to alter the distribution state of the absorption liquid within the packed tower. Full article
(This article belongs to the Section Purification Technology)
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13 pages, 4153 KiB  
Article
Effective Utilization of Sulfur Wastewater by Photocatalytic System Using B/CuO/ZnO
by Ikki Tateishi, Mai Furukawa, Hideyuki Katsumata and Satoshi Kaneco
Separations 2024, 11(1), 19; https://doi.org/10.3390/separations11010019 - 5 Jan 2024
Viewed by 1730
Abstract
B-doped zinc oxide/copper oxide composites prepared using a simple method showed high photocatalytic hydrogen production activity in the presence of aqueous sulfide solutions. Co-modification of the CuO composite with B-doping caused an increase in the charge separation efficiency and light absorption capacity. The [...] Read more.
B-doped zinc oxide/copper oxide composites prepared using a simple method showed high photocatalytic hydrogen production activity in the presence of aqueous sulfide solutions. Co-modification of the CuO composite with B-doping caused an increase in the charge separation efficiency and light absorption capacity. The sacrificial effect was thermodynamically enhanced by manipulating the composition of the sulfide solution. A maximum hydrogen production activity of 224 μmol g−1 h−1 was achieved under 450 nm light irradiation in a photocatalytic system with optimized B doping, a CuO composite, and a sulfide sacrificial agent concentration. Full article
(This article belongs to the Section Purification Technology)
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12 pages, 3019 KiB  
Article
A Cyanoalkyl Silicone GC Stationary-Phase Polymer as an Extractant for Dispersive Liquid–Liquid Microextraction
by Mohamed A. Abdelaziz and Neil D. Danielson
Separations 2024, 11(1), 18; https://doi.org/10.3390/separations11010018 - 5 Jan 2024
Viewed by 1814
Abstract
In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through [...] Read more.
In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through the DLLME of four non-steroidal anti-inflammatory drugs from aqueous samples, followed by HPLC separation with UV detection at 230 nm. To achieve the maximum enrichment, the experimental conditions that influence the DLLME process were optimized using one-factor-at-a-time and design-of-experiment (DoE) approaches. The extraction variables (polymer mass, dispersive solvent volume, buffer pH, and mixing time) were screened by implementing a two-level full factorial design (FFD). Significant variables were fine-tuned using response surface methodology based on a face-centered central composite design (CCD). The optimum conditions were 10 mg of polymer (extraction medium); 50 µL of tetrahydrofuran (dispersive solvent); 100 µL of phosphate buffer pH 2.75 ([PO43−] = 100 mM); and 3 min of vortex mixing. The addition of salt had a minimal effect on the enrichment factors. In the optimum conditions, enrichment factors up to 46 were achieved using 1.5 mL samples. Calibration curves exhibited correlation coefficients > 0.999 using 4-pentylbenzoic acid as an internal standard. The limits of quantitation were 5 ng/mL for naproxen, 10 ng/mL for diflunisal, 25 ng/mL for indomethacin, and 75 ng/mL for ibuprofen. The analysis of spiked tap water samples showed adequate relative recoveries and precision. In conclusion, the proposed polymer (OV-225) is a potential greener alternative to traditional organic extractants used in DLLME. Full article
(This article belongs to the Collection Feature Paper Collection in Section 'Materials in Separation Science')
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19 pages, 9851 KiB  
Article
Adsorption Performance and Mechanism of H3PO4-Modified Banana Peel Hydrothermal Carbon on Pb(II)
by Tao Bai, Yuhu Yao, Jiaxin Zhao, Laixin Tian and Luming Zhang
Separations 2024, 11(1), 17; https://doi.org/10.3390/separations11010017 - 3 Jan 2024
Cited by 5 | Viewed by 2078
Abstract
This study investigated the adsorption performance of hydrothermal carbon derived from banana peel and modified with different concentrations of phosphoric acid solution, then used to adsorb lead ions in an aqueous solution. The surface structure and functional groups of the modified hydrothermal carbon [...] Read more.
This study investigated the adsorption performance of hydrothermal carbon derived from banana peel and modified with different concentrations of phosphoric acid solution, then used to adsorb lead ions in an aqueous solution. The surface structure and functional groups of the modified hydrothermal carbon were analyzed using XRD, SEM, FT-IR, elemental analysis, and BET. The results showed that the adsorption capacity of modified hydrothermal carbon derived from banana peel reached 40.64 mg/g at a hydrothermal temperature of 240 °C, a phosphoric acid solution of 2 mol/L, and a solid–liquid ratio of 2 g/L, with a removal efficiency of 82.74%. The adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir isotherm equation. The correlation coefficient of 0.99 for fitting the adsorption process using an artificial neural network, indicating that the artificial neural network could be used to predict adsorption. The adsorption of Pb(II) from an aqueous solution by phosphoric acid-modified hydrothermal carbon was dominated by monolayer chemical adsorption, and the adsorption mechanisms included electrostatic attraction, ion exchange, surface complexation, and physical adsorption. Full article
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17 pages, 7327 KiB  
Article
Prediction of Bleeding via Simulation of Hydrodynamics in Centrifugal Partition Chromatography
by Felix Buthmann, Sophia Volpert, Jörg Koop and Gerhard Schembecker
Separations 2024, 11(1), 16; https://doi.org/10.3390/separations11010016 - 3 Jan 2024
Cited by 3 | Viewed by 1770
Abstract
Centrifugal Partition Chromatography (CPC) utilizes a two-phase liquid–liquid system as mobile and stationary phases. During operation, the latter continuously drains out of the rotor, despite it being in fact stationary, leading to decreasing separation efficiency over time, a phenomenon still poorly understood today [...] Read more.
Centrifugal Partition Chromatography (CPC) utilizes a two-phase liquid–liquid system as mobile and stationary phases. During operation, the latter continuously drains out of the rotor, despite it being in fact stationary, leading to decreasing separation efficiency over time, a phenomenon still poorly understood today because neither simulations nor extensive experimental investigations have addressed this so-called bleeding. With the model presented in this study, the underlying hydrodynamics are discussed in detail. This model can simulate bleeding over 60 s and is verified experimentally for different operating points (volumetric flow rates of 5, 12, and 20 mL⋅min−1) of the Centrifugal Partition Chromatograph utilizing an aqueous–organic phase system. We simulated two interconnected chambers at the rotor inlet and analyzed the loss of the stationary phase over time. The results of the simulated second chamber are closely aligned with the experimental validation results. Thus, the prediction of bleeding utilizing the simulation of hydrodynamics was successful. Moreover, we highlighted the benefits of the two-chamber setup modeled in this study compared to single-chamber models. Full article
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10 pages, 1496 KiB  
Article
Isolation and Chemotaxonomic Implications of Tenelloside, a Novel Unusual C-Glycosyl Flavanone from Phyllanthus tenellus Roxb. in Tenerife Island
by Antonio Francioso, Ignacio Antonio Jiménez Díaz, Carolina Pérez Reyes, Cristina González Montelongo, Marco Pierini, Claudio Villani and Isabel López Bazzocchi
Separations 2024, 11(1), 15; https://doi.org/10.3390/separations11010015 - 31 Dec 2023
Viewed by 1948
Abstract
Phyllanthus is a large genus of the Euphorbiaceae family, which has been widely used in traditional medicine. The current study reports the isolation of an unusual C-glycosyl flavonoid, named tenelloside, from Phyllanthus tenellus Roxb., a non-endemic plant present in Canary Islands. The [...] Read more.
Phyllanthus is a large genus of the Euphorbiaceae family, which has been widely used in traditional medicine. The current study reports the isolation of an unusual C-glycosyl flavonoid, named tenelloside, from Phyllanthus tenellus Roxb., a non-endemic plant present in Canary Islands. The chemical structure of this secondary metabolite was established employing combined spectrometric and spectroscopic techniques, including 1D and 2D NMR experiments and mass spectrometry. The absolute stereochemical configuration was determined via the comparison of experimental and calculated electronic circular dichroism spectra. In our previous work, another C-glycosylated bioactive product was isolated from another Phyllanthus species, suggesting that this class of compounds can be produced in a genus-specific manner in different geographic regions. This work represents another important report for direct future studies on the biological and chemotaxonomic potential of C-glycosylated products of the Phyllanthus genus. Full article
(This article belongs to the Special Issue Novel Applications of Separation Technology)
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12 pages, 1339 KiB  
Article
Composition of Essential Oils from Fruits of Peucedanum longifolium and Rhizomatophora aegopodioides (Apiaceae) with Regard to Other Related Taxa—A Chemometric Approach
by Ljuboš Ušjak, Marjan Niketić and Silvana Petrović
Separations 2024, 11(1), 14; https://doi.org/10.3390/separations11010014 - 30 Dec 2023
Viewed by 1584
Abstract
The aim of this work was to investigate the composition of essential oils isolated from fruits of Peucedanum longifolium, and Rhizomatophora aegopodioides (a species which was previously placed in the genus Peucedanum), as well as to compare the obtained results to [...] Read more.
The aim of this work was to investigate the composition of essential oils isolated from fruits of Peucedanum longifolium, and Rhizomatophora aegopodioides (a species which was previously placed in the genus Peucedanum), as well as to compare the obtained results to those available for other previously investigated related species (including taxa which are also, according to some authors, excluded from the genus Peucedanum). Essential oils were obtained via hydrodistillation in a Clevenger-type apparatus and their composition was analyzed using GC-FID and GC-MS. To compare these data to those of previously investigated taxa, a chemometric approach was applied; the data were analyzed using multivariate statistical methods: non-metric multidimensional scaling (nMDS) and hierarchical cluster analysis. The most abundant in P. longifolium essential oil were monoterpenes (79.7%), mostly α-phellandrene (26.2%), β-phellandrene + limonene (21.0%) and myrcene (9.5%), followed by sesquiterpenes (18.3%), mostly germacrene B (9.5%). On the other hand, dominant in R. aegopodioides essential oil were non-terpenic aliphatic hydrocarbons (46.1%), mainly n-undecane (16.5%) and n-nonane (11.3%). In addition, this essential oil also contained a notable quantity of sesquiterpenes (25.1%), with (E)-sesquilavandulol being the most abundant (10.0%). The results of multivariate statistics revealed a clear separation of the essential oil composition of R. aegopodioides and P. longifolium, as well as of P. longifolium and P. officinale. The clustering of the samples of most of the taxa that do not belong to the Peucedanum in the narrow sense (sensu stricto) was also observed, which is in accordance with their recent inclusion in separate genera. Full article
(This article belongs to the Special Issue Applications of Separation and Purification Techniques for Natural Products Derived from Plants Source)
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15 pages, 2880 KiB  
Article
Optimization of the Extraction of Bioactive Compounds from Cabernet Sauvignon Grape Pomace from Querétaro, Mexico, Using MSPD
by Tellez-Robles Daniela, López-Cortez Ma. del Socorro, Santoyo-Tepole Fortunata, Rosales-Martínez Patricia, García-Ochoa Felipe, Hernández-Botello Mayuric Teresa and Salgdo-Cruz María de la Paz
Separations 2024, 11(1), 13; https://doi.org/10.3390/separations11010013 - 28 Dec 2023
Cited by 5 | Viewed by 2062
Abstract
Red wine contains polyphenols which are extracted during the winemaking process. However, winemaking is not an extraction; therefore, the resulting byproducts still have a substantial polyphenol content. The aim of this study was to compare two methods for the extraction of phenolic compounds: [...] Read more.
Red wine contains polyphenols which are extracted during the winemaking process. However, winemaking is not an extraction; therefore, the resulting byproducts still have a substantial polyphenol content. The aim of this study was to compare two methods for the extraction of phenolic compounds: maceration and matrix solid-phase dispersion (MSPD). Grape pomace (Vitis vinifera var. Cabernet Sauvignon) from a winery in Querétaro, Mexico was used. The optimal conditions for both methods were identified. Phenolic compounds and antioxidant activity were the response variables. A central composite design was used (Minitab 17) for the extraction by maceration. The maceration time (1, 4, 12, 20, and 24 h) and the ratio of ethanol (50 to 80%) acidified with 1% HCl were the two factors studied. For the MSPD extraction, sea sand was used as a dispersant, and a 22 factorial design was employed for the evaluation, with the elution volume and the ratio of sample/dispersant being the two factors analyzed. The optimal extraction method was MSPD with 96 mL (acidified ethanol) as the elution volume and a 1:2 ratio of sample/dispersant. Using these conditions, 14.01 ± 0.19 mMol TEAC/100 g db (Trolox equivalent of antioxidant capacity) of grape pomace was obtained, whereas the total phenolic content was 2836.73 ± 41.90 mg GAE/100 g db. These values are greater than those obtained by maceration. These conditions are close to those predicted by the model (analysis of variance (ANOVA) with a level of significance of 5% (p < 0.05) and a Tukey comparison test for determining significant differences in the comparison of results). Full article
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18 pages, 5044 KiB  
Article
Application of the Biomass of Leaves of Diospyros kaki L.f. (Ebenaceae) in the Removal of Metal Ions from Aqueous Media
by Rodrigo Martorelli Galera, Adrielli Cristina Peres da Silva, Alexandre de Oliveira Jorgetto, Marcos Henrique Pereira Wondracek, Margarida Juri Saeki, José Fabián Schneider, Valber de Albuquerque Pedrosa, Marco Autônio Utrera Martines and Gustavo Rocha Castro
Separations 2024, 11(1), 12; https://doi.org/10.3390/separations11010012 - 27 Dec 2023
Viewed by 1761
Abstract
Using straightforward and cost-effective methods, persimmon leaves were converted into high-quality powder. This powder was applied as an adsorbent for the removal of Cu(II) and Cd(II) from aqueous solutions. Scanning electron microscopy (SEM) revealed the presence of particles with non-homogeneous sizes and rough [...] Read more.
Using straightforward and cost-effective methods, persimmon leaves were converted into high-quality powder. This powder was applied as an adsorbent for the removal of Cu(II) and Cd(II) from aqueous solutions. Scanning electron microscopy (SEM) revealed the presence of particles with non-homogeneous sizes and rough textures. The biosorbent exhibited a specific surface area of approximately 0.44 ± 0.015 m2 g−1. Elemental analysis and energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of elements such as sulfur, phosphorus, nitrogen, and oxygen. The results of 13C nuclear magnetic resonance (13C-NMR), obtained using the cross-polarization technique, show the presence of groups containing sulfur and oxygen. Infrared spectroscopy (FTIR) indicated the existence of amine and hydroxyl groups. The material was used in the solid-phase extraction of Cu(II) and Cd(II) in batch experiments, and its adsorption capacity was evaluated as a function of time, pH, and analyte concentration. The fraction with a diameter between 63 and 106 μm was selected for the adsorption tests. Kinetic equilibrium was reached within 5 min, and the experimental data were fitted to the pseudo-second-order kinetic model. The optimum pH for the adsorption of both metal species was approximately 5.0. The adsorption isotherms were adjusted using the modified Langmuir equation, and the maximum amount of metal species extracted from the solution was determined to be 0.213 mmol g−1 for Cu(II) and 0.215 mmol g−1 for Cd(II), with high linear correlation coefficients for both metals. Persimmon leaves are typically abundant during the growing season, and because they are seasonal, the Diospyros kaki L.f. tree undergoes the natural process of leaf abscission, ensuring the availability of leaves for application. Full article
(This article belongs to the Special Issue Separation Process through Adsorption for Sustainable Utilization of Bioresources)
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22 pages, 663 KiB  
Review
Sulfolane Analysis in Environmental Samples: A Critical Review
by Merrik Kobarfard and Tadeusz Górecki
Separations 2024, 11(1), 11; https://doi.org/10.3390/separations11010011 - 27 Dec 2023
Viewed by 2197
Abstract
Sulfolane, a highly water-soluble industrial solvent, has raised environmental concerns due to its widespread usage and its prolonged persistence once released into the environment. To assess the extent of contamination effectively, reliable analytical methods are essential. In this review article, the existing methodologies [...] Read more.
Sulfolane, a highly water-soluble industrial solvent, has raised environmental concerns due to its widespread usage and its prolonged persistence once released into the environment. To assess the extent of contamination effectively, reliable analytical methods are essential. In this review article, the existing methodologies for the sample preparation and determination of sulfolane are systematically examined and evaluated. In brief, existing guidelines for sampling from environmental matrices provide a solid foundation for sulfolane analysis. Notably, there is little variation in the choice of final determination methods, with GC-MS or GC-FID being favored across all studies. However, substantial variability emerges in sample preparation methods. Moreover, upon scrutiny of the analytical procedures utilized in sulfolane analysis, it becomes evident that a considerable number of them are characterized by inefficiency or environmental hazards, often relying on substantial quantities of chlorinated solvents. Through this review, valuable insights into the challenges at hand and potential solutions can be gained, offering a foundation for the development of novel sulfolane analysis methods applicable to a range of environmental matrices. Overall, this field calls for further research to devise efficient and environmentally sustainable analytical methods for sulfolane analysis. Full article
(This article belongs to the Collection Feature Paper Collection in Section Chromatographic Separations)
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19 pages, 4864 KiB  
Article
Applicable Pharmacokinetic Study: Development and Validation of Bioanalytical LC-MS/MS Method for Simultaneous Determination of Tipiracil, Trifluridine and Its Two Metabolites 5-Trifluoromethyluracil, 5-Carboxy 2′-Deoxyuridine in Rat Plasma
by Manal El-Gendy, Mohamed Hefnawy, Adeeba Alzamil, Adel El-Azab, Alaa Abdel-Aziz and Ali El Gamal
Separations 2024, 11(1), 10; https://doi.org/10.3390/separations11010010 - 26 Dec 2023
Viewed by 1900
Abstract
A novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the simultaneous determination of tipiracil (TIP), trifluridine (FTD), and their metabolites, 5-trifluoromethyluracil (FTY) and 5-carboxy-2′-deoxyuridine (5CDU), in rat plasma. This method is highly sensitive, specific, and fast. Paracetamol (PAR) [...] Read more.
A novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the simultaneous determination of tipiracil (TIP), trifluridine (FTD), and their metabolites, 5-trifluoromethyluracil (FTY) and 5-carboxy-2′-deoxyuridine (5CDU), in rat plasma. This method is highly sensitive, specific, and fast. Paracetamol (PAR) is used as an internal standard (IS). Using acetonitrile-induced protein precipitation, the analytes were extracted from a plasma sample and separated on a Waters BEH C18 (1.7 μm particle size, 50 mm × 2.1 mm ID) column protected by a security guard cartridge (C18, 4 × 2.0 mm). The isocratic mobile phase was made up of methanol and water containing 0.1% formic acid (80:20, v/v) at a flow rate of 0.5 mL/min for 4 min. The quantification was performed using a positive electrospray ionization (ESI) interface and a multiple-reaction monitoring (MRM) mode. The MRM transitions employed were m/z 242.96 → 182.88 for TIP, 296.96 → 116.86 for FTD, 180.98 → 139.85 for FTY, 272.96 → 156.86 for 5CDU, and 151.97 → 92.68 for IS. The validated method complied with the guidelines set by the US-FDA over on a linear concentration range of 5–4000 ng/mL for FTD, FTY, and 5CDU, and 5–1000 ng/mL for TIP. The coefficient of determination (r2) was equal to or greater than 0.997. The corresponding lower limits of detection (LLOD) were 1.5 ng/mL for FTD, FTY, and 5CDU and 1.0 ng/mL for TIP. The recoveries of all analytes from rat plasma ranged from 88.67% to 112.18%, and the mean relative standard deviation (RSD) of accuracy and precision result was less than or equal to 6.84%. FTD, FTY, 5CDU, and TIP demonstrated adequate stability throughout the various circumstances examined. Additionally, no matrix effects were identified for any of the analytes. The assay was effectively utilized to conduct a pharmacokinetic study in rats following the oral administration of FTD and TIP at a dosage of 5.6 mg/kg, with a ratio of 1:0.5 for FTD and TIP, respectively. This indicates that the suggested approach is suitable for future clinical research. The pharmacokinetic parameters Cmax (maximum concentration), Tmax (time to reach maximum concentration), t1/2 (half-life), AUC0-24 (area under the concentration–time curve from 0 to 24 h), AUC total (total area under the concentration–time curve), Ke (elimination rate constant), Vd (volume of distribution), and CL (clearance) of all analytes were assessed. The assay developed exhibits significant advancements compared to earlier bioanalytical methods documented in the literature. These improvements include high sensitivity, specificity, and efficacy in high throughput analysis of complex matrices. Additionally, the assay offers a shorter run time and smaller sample volume (50 μL). Full article
(This article belongs to the Special Issue Application of Hyphenated Techniques in Bioanalysis and Metabolite Identification)
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15 pages, 3439 KiB  
Article
Immobilisation of Molybdenum in a Sulphate-Reducing Bioreactor
by Pavlina Kousi, Dimitra-Artemis Strongyli, Petros E. Tsakiridis, Artin Hatzikioseyian and Emmanouella Remoundaki
Separations 2024, 11(1), 9; https://doi.org/10.3390/separations11010009 - 25 Dec 2023
Cited by 1 | Viewed by 1762
Abstract
This work presents a biological remediation process for molybdenum-bearing wastewater which may lead to the fabrication of biogenic Mo chalcogenide particles with (photo)catalytic properties. The process is based on dissimilatory sulphate reduction, utilising sulphate-reducing bacteria (SRB), and reductive precipitation of molybdate which is [...] Read more.
This work presents a biological remediation process for molybdenum-bearing wastewater which may lead to the fabrication of biogenic Mo chalcogenide particles with (photo)catalytic properties. The process is based on dissimilatory sulphate reduction, utilising sulphate-reducing bacteria (SRB), and reductive precipitation of molybdate which is the predominant species of molybdenum in oxygenated water/wastewater. The SRB culture was established in a biofilm reactor which was fed with synthetic solutions containing sulphate (17.7 mM), molybdate molybdenum (2 mM), divalent iron (1.7 mM) and ethanol as the carbon/electron donor. The performance of the bioreactor was monitored in terms of pH, sulphate and molybdenum (Mo(VI) and total) content. The presence of thiomolybdate species was studied by scanning UV-Vis absorbance of samples from the reactor outflow while the reactor precipitates were studied via electron microscopy coupled with energy dispersive spectrometry, X-ray diffractometry and laser light scattering. A molar molybdate/sulphate ratio of 1:12.5 proved effective for molybdate reduction and recovery by 76% in 96 h, whereas sulphate was reduced by 57%. Molybdenum was immobilised in the sulphidic precipitates of the bioreactor, presumably via two principal mechanisms: (i) microbially mediated reduction and precipitation, and (ii) thiomolybdate formation and sorption/incorporation into iron sulphides. Full article
(This article belongs to the Special Issue Separation and Recovery of Valuable Elements from Waste and Wastewater)
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14 pages, 1865 KiB  
Article
Method Development for Aminopyralid Residues Determination by Ultra-High-Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry in Straw
by Sebnem Kurhan, Kateřina Hanková, Pavel Klouček and Martin Koudela
Separations 2024, 11(1), 8; https://doi.org/10.3390/separations11010008 - 25 Dec 2023
Viewed by 2110
Abstract
Straw is an important by-product of crop production. It has been widely used as a feed as well as in fruit–vegetable production due to exerting a positive impact on soil and crop health and quality in the operated areas. On the other hand, [...] Read more.
Straw is an important by-product of crop production. It has been widely used as a feed as well as in fruit–vegetable production due to exerting a positive impact on soil and crop health and quality in the operated areas. On the other hand, applied crop-specific herbicides throughout the production stage, like aminopyralid (AP), may lead to significant plant injuries in sensitive vegetable plantations, even in very low concentrations. This study aims to optimize a short time, minimal consumables needed, and sensitive extraction and analytical method for AP residues in straw material using LC-MS/MS. For this purpose, standard AP signal response in acetonitrile (MeCN) and 1% of formic acid (FA) in methanol (MeOH) were tested; several chromatographic separation and mass spectroscopy (MS) parameters were improved and optimized. Subsequently, two different extraction methods were performed in AP spiked straw samples, and extraction efficacies were compared. Salting-out assisted liquid–liquid extraction (SALLE) by acidified MeCN combined with final dissolution in MeOH with 1% of FA prior to the analysis was chosen as the most appropriate method for the straw matrix. This method was then used for validation and real sample test analysis. The limit of quantification (LOQ) of AP in this optimized extraction method achieved 10 ng/g straw with a recovery rate of 71% and 13% RSD. The method was also tested on field straw mulch samples and 22.54 ± 0.8 ng/g of AP was detected. Full article
(This article belongs to the Section Environmental Separations)
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Article
Recovery of Valuable Metals from Polymetallic Refractory Concentrate by a Sulfuric Acid Curing and Leaching Method
by Wei Jiang, Jilai Xue, Kaixi Jiang, Xunxiong Jiang, Shengdong Wang, Jinping Hu, Derek O. Northwood, Kristian E. Waters and Hao Ma
Separations 2024, 11(1), 7; https://doi.org/10.3390/separations11010007 - 23 Dec 2023
Cited by 1 | Viewed by 1842
Abstract
Sulfuric acid curing and leaching is a promising technology for treating refractory ores. In this work, a refractory concentrate containing 3191 ppm uranium (U), 2135 ppm niobium (Nb), and 0.7% rare earth minerals (REMs) went through two stages: curing by high-concentration H2 [...] Read more.
Sulfuric acid curing and leaching is a promising technology for treating refractory ores. In this work, a refractory concentrate containing 3191 ppm uranium (U), 2135 ppm niobium (Nb), and 0.7% rare earth minerals (REMs) went through two stages: curing by high-concentration H2SO4 and leaching by low-concentration H2SO4. We investigated the behavior of those valuable metals during the two stages. For both curing and leaching, the operating parameters include the acid-to-solid ratio, time, temperature, and H2SO4 concentration. The recovery for U, Nb, and REMs was as high as 95%, 86%, and 73.5% using a curing acid-to-solid ratio of 1:1, curing temperature of 200 °C, curing time of 1 h, H2SO4 concentration of 98%, leaching liquid-to-solid ratio of 4:1, leaching time of 2 h, leaching temperature of 60 °C, and leaching H2SO4 concentration of 5 g/L. A “sulfuric acid curing–leaching-U extraction by N235–Nb recovery by resin adsorption–REMs’ recovery by resin adsorption” method was implemented, where the overall U, Nb, and REMs’ recovery reached 93.1%, 84.5%, and 69.6%, respectively. Full article
(This article belongs to the Special Issue Separation Methods in Mineral Industry)
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