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• HEIWat system was more suitable for large-polar compounds while P' decreases. • The selected solvent systems could be divided into group III and IV. • Proportion and type of solvents had different effects in different CCC systems. Solvent system selection based on polarity is a common strategy in a countercurrent chromatography (CCC) analysis. However, the solvent selectivity of solvent system is often ignored, despite its significant impact on the separation efficiency of CCC. In this study, the role of solvent in the overall properties of solvent system and the selective classification of solvent system were discussed to improve the solvent system selection based on polarity. Firstly, the mathematical relationship between logarithm of the partition coefficient (log K) of the template molecule and solvent composition of n-hexane/ethyl acetate/alcohol solvents (methanol, ethanol, and isopropanol)/water (HEAwat) system was analyzed and the optimal solvent system (K = 1) of the template molecules was determined. Then, the actual methanol concentration at the column inlet when the analyte peak in a HPLC analysis (B%) and the clustering results of the average polarity (P') of the optimal CCC solvent system were analyzed. Finally, the classification of HEAWat system in terms of its overall solvent properties by deducing equations of selectivity parameters (χ e , χ d , and χ n) to explain the P' values clustering results. The results showed that HEAWat system was suitable for the separation of analytes with 55 % < B % < 100 %. However, the n-hexane/ethyl acetate/isopropanol/water (HEIWat) system proved more suitable for the separation of large polar compounds to other HEAWat system when the P' value decreased due to the change of alcohol solvents. The selected solvent systems were classified into group III and IV by Snyder's method. The solvent systems in group III were suitable for the separation of analytes with 85 % < B % < 100 %, and the distribution behavior of analytes was mainly influenced by the ratio of each solvent. The solvent systems in group IV were suitable for the separation of analytes with 55 % < B % < 85 %, and the distribution behavior of analytes was mainly influenced by the type of alcohol solvents. [ABSTRACT FROM AUTHOR]

• Solent effect of different type of solvents were fully evaluated. • The most evident impact to solvent effect is the comparative retention of the solvent in RPLC regarding the separated components. • Extreme tolerance of n -hexane up to 1/4 of the column bed volume. • A flexible coupling of NPLC and RPLC method was established by using n -hexane based NPLC mobile system. Reversed-phase liquid chromatography (RPLC) represents an effective separation method, and is widely employed as the second dimension in most 2D-LC systems. Nevertheless, the solvent effect of the eluent from the first dimension on RPLC presents a challenge to the online coupling of RPLC with other separation modes, particularly normal phase liquid chromatography (NPLC). To address this issue, a comprehensive understanding of the solvent effect is essential. Following a comprehensive investigation into the influence of diverse solvents on RPLC separations, it was observed that alkane solvents, such as n -hexane, exhibited a pronounced tendency to be retained during RPLC separations. Such solvents do not affect the analysis of samples with weaker retention abilities than themselves, even when a large injection volume is used. The solvent effect was thus reduced by employing n -hexane-based solvent dilution. Leveraging the markedly enhanced solvent tolerance and extensive injection volume in RPLC, a versatile integration of the NPLC and RPLC was devised, necessitating merely a purge pump and a 10 port 2 position valve in conjunction with two sample loops. The novel 2D-LC system was then deployed for the analysis of propolis, a naturally occurring complex sample, and demonstrated remarkable separation efficiency. [ABSTRACT FROM AUTHOR]

• No alkyl-sulfonates are formed during the synthesis of sulfonate-salts. • Alkyl-sulfonate formation requires highly acidic conditions. • The use of semi-aqueous conditions also prevents alkyl-sulfonate formation. • Analytical data indicate that alkyl tosylates are absent from tosylate salts. • Solid-phase extraction could apply to detectable impurities like residual solvents. [ABSTRACT FROM AUTHOR]

• Developed solvent-free method for e-cigarette and heated tobacco product aerosols. • Concentrated aerosol collected mass extracted by squeezing from Cambridge filter pads. • Extraction method suitable for various constituents in e-cigarette aerosols. • Method inadequate for lipophilic constituents from heated tobacco product aerosols. Previous in vitro toxicological assessments have demonstrated that almost no mutagenic and genotoxic activities in electronic cigarette (e-cigarette) and heated tobacco product (HTP) aerosols were detected even at the maximum recommended concentration. To accurately compare the toxicity levels between cigarette smoke and e-cigarette or HTP aerosols, higher exposure concentrations increasing the possibility to detect toxicity in in vitro tests are necessary, while avoiding solvent-induced toxicity. This study aimed to develop a solvent-free extraction method to obtain concentrated aerosol extracts for improved toxicological evaluation. Our novel approach involved squeezing several Cambridge filter pads, which collected aerosol constituents, in closed containers to achieve solvent-free extraction with comparable efficiency to the conventional method using organic solvents. The optimized squeezing method yielded extracts with concentrations approximately 10 times higher than those obtained in conventional extraction methods. Yield comparison of various constituents, such as flavoring compounds, in e-cigarette aerosol extracts revealed similar extraction efficiencies between the squeezing and conventional methods. However, the extraction efficiency for constituents with high log P ow values, predominantly found in HTP aerosol extracts, was unacceptably low using the squeezing method. In addition, solvent-free centrifuging, another type of extraction method, exhibited unsatisfactory results for even e-cigarette aerosols compared with the conventional method. Our findings suggest that the solvent-free squeezing method is suitable for extracting aerosol collected mass from e-cigarette aerosol but not from HTP aerosol. We anticipate that the solvent-free squeezing method will contribute to a deeper understanding of toxicological differences between e-cigarettes and conventional combustible cigarettes. [ABSTRACT FROM AUTHOR]

• Organic-solvent ditch forms at the RPLC interface due to the hydrophobic effect. • The ditch carries excess of organic solvent compared with bulk mobile phase. • Ditch overlap is studied by molecular dynamics simulations in cylindrical mesopores. • Acetonitrile ditch overlap sets in at larger pore size than methanol ditch overlap. • Ditch has an impact on local and pore-averaged solvent composition and mobility. Mass transport through the mesopore space of a reversed-phase liquid chromatography (RPLC) column depends on the properties of the chromatographic interface, particularly on the extent of the organic-solvent ditch that favors the analyte surface diffusivity. Through molecular dynamics simulations in cylindrical RPLC mesopore models with pore diameters between 6 and 12 nm we systematically trace the evolution of organic-solvent ditch overlap due to spatial confinement in the mesopore space of RPLC columns for small-molecule separations. Each pore model of a silica-based, endcapped, C 18 -stationary phase is equilibrated with two mobile phases of comparable elution strength, namely 70/30 (v/v) water/acetonitrile and 60/40 (v/v) water/methanol, to consider the influence of the mobile-phase composition on the onset of organic-solvent ditch overlap. The simulations show that, as the pore diameter decreases from 9 to 6 nm, the bonded-phase density extends and compacts towards the pore center, which leads to increased accumulation of organic-solvent excess and thus enhanced organic-solvent diffusivity in the ditch. Because the acetonitrile ditch is more pronounced than the methanol ditch, acetonitrile ditch overlap sets in at less severe spatial confinement than methanol ditch overlap. The pore-averaged methanol and acetonitrile diffusivities are considerably raised by ditch overlap in the 6 nm-diameter pore, but also benefit from the ditch (without overlap) in the 7 to 12 nm-diameter pores, whereby local and pore-averaged effects are generally larger for acetonitrile than methanol. [ABSTRACT FROM AUTHOR]

• A fast and simple technique was proposed for extraction of methadone and tramadol. • Oxidized CNT was used as a new adsorbent for extraction of opiate drugs. • Parameters affecting the extraction of opiate drugs were studied and optimized. • Ultrasonic waves were used to enhance the speed of extraction and desorption. • Adding a very small amount of a salt makes the centrifugation conditions milder. Ultrasonic–assisted dispersive micro solid phase extraction (UA-DMSPE) is proposed as a fast and easy technique for the extraction and preconcentration of methadone and tramadol from serum samples. Different sorbents including carbon nanotubes, oxidized carbon nanotubes, and TiO 2 nanoparticles were compared to extract methadone and tramadol. The best performance was obtained using oxidized carbon nanotubes due to the strong affinity between the drugs and carbon nanotube adsorbents. Final analysis of drugs performed by using gas chromatography–mass spectrometric detection. Different parameters affecting the extraction efficiency, such as the sample volume, amount of adsorbent, desorption solvent type and volume, centrifugation time, and speed were investigated and optimized. The striking features of this technique are correlated to its speed and the small volumes of sample (about 1 mL), desorption solvent (about 50 μL), and adsorbent (about 0.001 g) for analysis of drugs, and finally, milder centrifugation conditions relative to the previously reported adsorbent. The optimal parameters were achieved as follows: pH value was set at 9, the sample volume was adjusted to 1200 µL, the amount of adsorbent used was 1 mg, the extraction time was set at 5 min, and the volume of the desorption solvent was adjusted to 50 µL. The limits of detections (0.5 and 0.8 ng mL−1) and quantifications (1.5 and 2.5 ng mL−1) were obtained for methadone and tramadol, respectively. The developed method also showed good repeatability, relative standard deviation (RSD) of 9.49 % and 7.47 % (n = 5), for the spiked aqueous solution at the concentration level of 10, 50, and 100 ng mL−1 for analytes, and linearity, R ≥ 0.9809. The results showed that UA-DMSPE is a quick, relatively inexpensive, and environmentally friendly alternative technique for the extraction of opiate drugs from serum samples. [ABSTRACT FROM AUTHOR]

• The DLLME-BE method enriches the dalbergia odorifera components in xiangdan injection. • The bar-form-diagram provides a more comprehensive reflection of the material foundation. • CRITIC-TOPSIS is proposed for quantitatively describe the multi-criteria optimization issue. • 29 components are characterized as the pharmaceutical foundation of XDI. Xiangdan Injection are commonly used traditional Chinese medicine formulations for the clinical treatment of cardiovascular diseases. However, the trace components of Dalbergia odorifera in Xiangdan Injection pose a challenge for evaluating its quality due to the difficulty of detection. This study proposes a technology combining dispersive liquid-liquid microextraction and back-extraction (DLLME-BE) along with Bar-Form-Diagram (BFD) to address this issue. The proposed combination method involves vortex-mixing tetradecane, which has a lower density than water, with the sample solution to facilitate the transfer of the target components. Subsequently, a new vortex-assisted liquid-liquid extraction step is performed to enrich the components of Dalbergia odorifera in acetonitrile. The sample analysis was performed on HPLC-DAD, and a clear overview of the chemical composition was obtained by integrating spectral and chromatographic information using BFD. The combination of BFD and CRITIC-TOPSIS strategies was used to optimize the process parameters of DLLME-BE. The determined optimal sample pre-treatment process parameters were as follows: 200 μL extraction solvent, 60 s extraction time, 50 μL back-extraction solvent, and 90 s back-extraction time. Based on the above strategy, a total of 29 trace components, including trans-nerolidol, were detected in the Xiangdan Injection. This combination technology provides valuable guidance for the enrichment analysis of trace components in traditional Chinese medicines. [ABSTRACT FROM AUTHOR]

• Dilution study to mitigate solvent mismatch challenges in HILIC x RPLC. • Model to predict minimum dilutions in HILIC x RPLC for optimal peak shape. • Predictions match experimental results, affirming HILIC x RPLC applicability. • Theoretical comparison of different LC x LC conditions. • Optimal conditions identified are RPLC x RPLC and 1:1 column diameter ratio. Online comprehensive two-dimensional liquid chromatography (online LC x LC) has become increasingly popular. Among the different chromatographic modes that can be combined, hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RPLC) are particularly interesting because they offer a high degree of orthogonality. However, this combination remains complex due to the incompatibility of the solvents in the two dimensions. To avoid this problem, it is possible to dilute the first dimension (1D) effluent with (z dilution -1) volumes of a weaker solvent added to one volume of 1D-effluent, where z dilution represents the extent to which the fraction volume has been multiplied. This can be done using either active solvent modulation technology or an additional pump, prior to the second dimension analysis. The objective of this study was to develop theoretical models to predict whether or not dilution can be effective, and, if so, what is the minimum z dilution value required. This approach is based on the calculation of the ratio (called x dilution) between the peak standard deviation due to the injection process and the peak standard deviation in the absence of extra-column dispersion. x dilution was calculated from theoretical relationships and plotted as a function of z dilution , to predict the value required to obtain good peak shapes for the compound of interest. The maximum x dilution value was found to be of the order of 1 for chromatographically acceptable peak shapes. The proposed theoretical approach was experimentally validated on a number of representative small molecules and peptides. Agreement between experimental results and theoretical models was very high, especially for small molecules. Finally, it is shown that this approach helps to predict the most appropriate set of conditions in HILIC x RPLC, depending on the compounds to be separated. [ABSTRACT FROM AUTHOR]

The covalent attachment of polyoxometalates (POMs) to polymers has been developed as a strategic approach for the advancement of POM-based hybrid materials with versatile applications. In this study, we utilized thiol-maleimide Michael addition to investigate the kinetics and efficacy of the "one-to-one" conjugation between Keggin type POM and polystyrene. We explored the effects of solvent polarity, catalyst, molecular weight of PS and synthetic strategies on the reaction kinetics and efficiency, by means of reverse-phase high-performance liquid chromatography (RP-HPLC). A series of comparative analysis affirmed the superior efficiency of the one-pot method, particularly when facilitated by the addition of a high-polarity solvent and an excess of maleimide. These findings offer valuable insights into the intricate interplay between reaction conditions, kinetics, and selectivity in thiol-maleimide reactions of POMs and polymers. They hold profound implications for advancing the study of POM-based multifunctional materials and the synthesis of complex hybrid molecules., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Hao Liu reports financial support was provided by National Natural Science Foundation of China. Hao Liu reports financial support was provided by Science and Technology Commission of Shanghai Municipality. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Immunoglobulin G (IgG) is the most common monoclonal antibody (mAb) grown for therapeutic applications. While IgG is often selectively isolated from cell lines using protein A (ProA) chromatography, this is only a stepping stone for complete characterization. Further classification can be obtained from weak cation exchange chromatography (WCX) to determine IgG charge variant distributions. The charge variants of monoclonal antibodies can influence the stability and efficacy in vivo, and deviations in charge heterogeneity are often cell-specific and sensitive to upstream process variability. Current methods to characterize IgG charge variants are often performed off-line, meaning that the IgG eluate from the ProA separation is collected, diluted to adjust the pH, and then transferred to the WCX separation, adding time, complexity, and potential contamination to the sample analysis process. More recently, reports have appeared to streamline this separation using in-line two-dimensional liquid chromatography (2D-LC). Presented here is a novel, 2D-LC coupling of ProA in the first dimension ( 1 D) and WCX in the second dimension ( 2 D) chromatography. As anticipated, the initial direct column coupling proved to be challenging due to the pH incompatibility between the mobile phases for the two stages. To solve the solvent compatibility issue, a size exclusion column was placed in the switching valve loop of the 2D-LC instrument to act as a means for the on-line solvent exchange. The efficacy of the methodology presented was confirmed through a charge variant determination using the NIST monoclonal antibody standard (NIST mAb), yielding correct acidic, main, and basic variant compositions. The methodology was employed to determine the charge variant profile of IgG from an in-house cultured Chinese hamster ovary (CHO) cell supernatant. It is believed that this methodology can be easily implemented to provide higher-throughput assessment of IgG charge variants for process monitoring and cell line development., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: R. Kenneth Marcus reports financial support was provided by National Science Foundation. Sarah W. Harcum reports financial support was provided by National Science Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

• A new high density DES as the extraction solvent was synthesized and used in DLLME. • It was used in determination of pesticides at ng g−1 level in honey. • High EFs, low LODs, and good repeatability were obtained. • The LOQs were lower than the MRLs established for the analytes in the studied samples. A green dispersive liquid–liquid microextraction using a new high density deep eutectic solvent (as an extraction solvent) has been developed and utilized in the simultaneous preconcentration and extraction of seven pesticides in honey followed by gas chromatography–flame ionization detection. The deep eutectic solvent is synthesized using menthol (as a hydrogen bond acceptor) and dichloroacetic acid (as a hydrogen bond donor) at a molar ratio of 1:2. Initially the analytes are extracted into acetone from the sample. After centrifuging, the synthesized deep eutectic solvent is added to the extract obtained from the previous step. Then this mixture is quickly injected into deionized water by a syringe for more concentration. A cloudy solution is formed by dispersion of fine droplets of the deep eutectic solvent by acetone into the aqueous solution and the pesticides are transferred into the extraction solvent. After extraction, phase separation is performed by centrifugation and the enriched analytes in the sedimented phase are determined. The influence of different parameters affecting the extraction efficiency was investigated and optimized. Under the optimized extraction conditions, enrichment factor for the analytes was obtained in the range of 279–428 with extraction recovery of 56–86%. Limits of detection and quantification were obtained in the ranges of 0.32–1.2 and 1.1–4.0 ng g−1, respectively. Relative standard deviations were ≤ 7% for intra– (n = 6) and inter–day (n = 5) precisions calculated at two concentrations of 10 and 50 ng g−1 of each analyte. Finally, some honey samples were effectively analyzed by the proposed method and diazinon was determined at ng g−1 concentration in one sample. [ABSTRACT FROM AUTHOR]

• The effect of sample solvent is studied in SFC with no modifier present. • Competitive adsorption is induced between methanol and the solutes. • Single-component bi-Langmuir isotherms were determined by the inverse method. • Simulations showed the competition for several solute-solvent combinations. • Sample solvent and solute may compete for adsorption. Uncommon retention behavior of a series of n -alkylbenzene homologues as well as the effect of different sample solvents on chromatographic efficiency were studied in supercritical fluid chromatography. After testing various columns, an alkylamide stationary phase was selected for detailed studies. The results showed that even a small amount of methanol originating only from the sample, overloaded the column and competitive adsorption was induced between the analytes and the sample solvent for adsorption on the stationary phase. This was indicated by the changes in column efficiency, retention and peak widths. The concentration of the analytes in the sample was negligible compared to the amount of methanol – but their adsorption was influenced by the solvent – while the adsorption of methanol remained unaffected by the n -alkylbenzenes. First, the competition was described by determining the single-component adsorption isotherms for both the analytes and their solvent, then competitive isotherms were calculated. Based on the peak profiles, bi-Langmuir and competitive bi-Langmuir isotherms were assumed. The solvent effect was modeled by a numerical method created in-house where the differential mass balance equation given by the equilibrium–dispersive (ED) model was integrated using the Rouchon algorithm. The experimental observations were confirmed by in silico experiments and additional cases involving two hypothetical analytes were studied as well. [ABSTRACT FROM AUTHOR]

• A novel adsorbent was prepared for magnetic solid phase extraction. • Varieties of experiment factors were optimized and selected. • Good aqueous dispersibility endow Fe 3 O 4 @PDA-DES with high enrichment performance. • This method has been successfully applied in the analysis of water samples. A novel magnetic solid-phase extraction (MSPE) technique coupled with ultra performance liquid chromatography (UPLC) has been developed for the determination of four sulfonylurea herbicides (sulfosulfuron, bensulfuron-methyl, pyrazosulfuron-ethyl and halosulfuron-methyl) in aqueous samples. The key point of this method was the application of a novel magnetic nanomaterial (Fe 3 O 4 @ PDA-DES). The functional groups, morphology, and magnetic properties of this magnetic nanomaterial were investigated through fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and X-ray diffraction (XRD) respectively. The main factors which could affect the experiment results were optimized. Under the optimum conditions, the linearity of this method ranged from 5.0–200 μg L−1 for all analytes, with correlation coefficients (r) ≥0.9901. The enrichment factors were between 495 and 630, and the relative standard deviations (RSDs) were less than 3.6%. The limits of detections (LODs) varied from 0.0098 to 0.0110 μg L-1. In the final experiment, the developed method has been successfully applied to the determination of sulfonylurea herbicides in environment and drinking water samples, and the obtained recoveries were between 61.3% and 108.6%. [ABSTRACT FROM AUTHOR]

• A deep eutectic solvent based MSPD is presented. • Graphitic carbon nitride was used as solid dispersant and sorbent. • The method was applied for the determination of some nitrotoluenes in soil samples. • The proposed method is green, simple, fast and cost-effective. In this research, a miniaturized version of matrix solid phase dispersion (MSPD) method was developed for successful extraction of five nitrotoluenes from soil samples. The terpene based deep eutectic solvent (DES) composed of borneol and DL-menthol was used simultaneously as extraction solvent and dispersing liquid. Graphitic-carbon nitride (g-C 3 N 4) as sorbent was prepared by pyrolysis of melamine at a muffle furnace. The MSPD mixture was obtained by grinding soil, DES, and g-C 3 N 4. Minimum amount of acetonitrile was used in the elution step. Some experimental variables including type and volume of DES, type of dispersant, mass ratio of dispersant to sample, volume of elution solvent, grinding time, and ultrasonication time were evaluated. Analysis of extracted samples was performed by high performance liquid chromatography-ultra violet detection. Under the optimized conditions; the limits of detection were achieved in the range of 0.12−0.33 μg g−1, and the relative standard deviations were equal to or lower than 9.3%. The extraction recoveries were ranged from 78 to 96%. This straightforward and fast method is effective for environmentally friendly extraction of nitrotoluenes from soil samples. [ABSTRACT FROM AUTHOR]

Highlights • A new high-density SUPRAS based on HFIP and Brij-35 was introduced. • Small amount of HFIP reduced the high cloud point of Brij-35 to room temperature. • The SUPRAS-based LPME method was proposed to enrich parabens in water and PPCPs. • The method showed high extraction capacity for parabens in wide range of polarity. • The method was easily performed at room temperature with normal centrifuge tubes. Abstract A novel supramolecular solvent (SUPRAS) based on hexafluoroisopropanol (HFIP)/Brij-35 was proposed for liquid-phase microextraction (LPME) of parabens in water samples, pharmaceuticals and personal care products. Brij-35 is a cost-effective and non-toxic non-ionic surfactant, but it has a high cloud point (>100 °C). HFIP, with the features of strong hydrogen-bond donor, high density and powerful hydrophobicity, was used as the cloud point-reducing agent and self-assembling and density-regulating solvent of Brij-35. Upon adding HFIP into the Brij-35 aqueous solution, the cloud point of Brij-35 was decreased to below room temperature, and the SUPRAS was formed in the bottom over a wide range of HFIP and Brij-35 concentrations at room temperature. The SUPRAS was composed of Brij-35, HFIP and water, having a density larger than water, and it showed a large spherical structure of positive micellar aggregates (2–8 μm). The HFIP/ Brij-35 SUPRAS-based LPME procedure was non-thermodependent and could be performed at room temperature with centrifugation using normal centrifuge tubes, being very simple. In the extraction of six parabens, the HFIP/ Brij-35 SUPRAS-based LPME method showed short extraction time (3.3 min), low solvent consumption (0.3 mL), and large enrichment factor (26–193). The method of HFIP/ Brij-35 SUPRAS-based LPME with HPLC-DAD gave good linearity for the quantification of parabens with correlation coefficients larger than 0.9990. The limits of detection based on a signal-to-noise ratio of 3 were from 0.042 to 0.167 μg L−1. The recoveries for the spiked real samples were in the range of 90.2–112.4% with relative standard deviation less than 8.9%. Except for tap water, one or several paraben (s) were detected in all the other real samples. [ABSTRACT FROM AUTHOR]

Highlights • 1 Five kinds of hydrophobic DESs were designed and prepared for the first time. • 2 The prepared DESs showed high extraction efficiency for formaldehyde (HCHO). • 3 The DES was applied to extract and determine of HCHO in biological and gas samples. • 4 Hydrophobic DESs based VA-LLME combined with HPLC method was developed. Abstract Hydrophobic deep eutectic solvents (DESs) are a new class of green solvents, and their research and application are a brand new area. So far, only a few hydrophobic DESs have been reported as extraction solvents. In this paper, five kinds of hydrophobic DESs composed of trioctylmethylammonium chloride and hydroquinone, 4-phenylphenol or 4-cyanophenol are designed and prepared for the first time. Melting point / glass transition temperature and density are also determined for these DESs. Coupled with HPLC, these hydrophobic DESs have been used as extractants in vortex-assisted liquid-liquid microextraction for the selective enrichment and indirect determination of formaldehyde. The optimization of reaction and extraction conditions, such as pH value, reaction time and temperature, concentration of 2,4-dinitrophenylhydrazine, type and dosage of the extraction solvent, speed and time of vortex, salt addition and centrifugation time are investigated in detail. It is found that under the optimized experimental conditions, the calibration curve of this method is linear in the range of 1.0–200.0 μg L−1 with the linear correlation coefficient (r2) of 0.9994. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) are 0.2 μg L−1 and 1.0 μg L−1, and the intra-day and inter-day precision (RSD, n = 5) are 1.1% and 3.5%, respectively. The interference of some common coexisting ions and neutral molecules have been also tested. The proposed method has been successfully used for the determination of formaldehyde from biological and indoor air samples. The recovery of formaldehyde is in the range from 83.1% to 104.4%, and the relative standard deviation is lower than 5.9%. Furthermore, the analytical parameters of the proposed method have been compared with other extraction and microextraction methods. [ABSTRACT FROM AUTHOR]

• The SUPRAS prepared by 1-octanol and THF was used for the extraction of coumarins. • The composition, viscosity, structure and micromorphology of SUPRAS were studied. • The extraction mechanism of SUPRAS was explored by inverted fluorescence microscope. • The extraction conditions were optimized using OFAT, RSM and ANN-GA. • In present method, less extraction time and extraction solvent were consumed. A simple, fast, and efficient ultrasonic-assisted supramolecular solvent microextraction combined with high performance liquid chromatography method was developed for the determination of coumarins in Cortex fraxini , including esculin, esculetin and fraxetin. In this study, a novel supramolecular solvent was prepared with 1-octanol, tetrahydrofuran and water for the first time, and its composition, viscosity, density, structure, and micromorphology were characterized. The prepared supramolecular solvent exhibited vesicular structures and had the characteristics of low viscosity. Through single-factor experiments, response surface methodology and artificial neural network-genetic algorithm, the optimal extraction conditions were obtained as follows: NaCl concentration of 1 mol mL−1, pH value of 10, solid-liquid ratio of 10:1, vortex time of 30 s, ultrasonic power of 100 W, ultrasonic temperature of 60 °C, ultrasonic time of 15 min, centrifugation speed of 5000 rpm, and centrifugation time of 1 min. The results demonstrated that the artificial neural network model exhibited maximum R -values of 0.98703, 0.97440, 0.99836, and 0.95447 for training, testing, validation, and all dataset, respectively. The minimum mean square errors were 0.75, 10.15, 1.99, and 2.63, respectively. This indicated that the predicted values were almost consistent with the actual values. Under the optimal conditions, the total extraction yields of target analytes reached 2.80 %. The calibration curves for each analyte exhibited excellent linearity within the linear range (r > 0.9993). The limits of detection and quantification ranged from 4.87 to 6.55 ng mL−1 and 16.24 to 21.84 ng mL−1, respectively. The recoveries ranged from 98.71 % to 111.01 % with relative standard deviations of less than 3.6 %. The present method had the advantages of short extraction time (15 min) and less solvent consumption (0.5 mL). The prepared supramolecular solvent was proved to have great potential in extracting coumarins from medicinal plants. [ABSTRACT FROM AUTHOR]

• The first successful application of DESs as separation media in CE. • A comprehensive assessment of the fundamental aspects of this DES-type CE medium. • The first observation of Tween micelles in a DES. • The DES-type CE medium can be used for establishing both CZE and MEKC systems. Capillary electrophoresis (CE) has conventionally been classified into aqueous and non-aqueous categories based on the types of buffer solvents employed. Traditionally, non-aqueous CE has always been associated with the use of organic solvents, which are considered hazardous to health and environmentally detrimental. In this work, we introduce deep eutectic solvents (DESs) as CE separation media for the first time, presenting a novel and environmentally friendly approach to CE separations. The DES employed consists of proline and urea (Proline:Urea, PU), both of which are naturally occurring compounds that are readily available, cost-effective, and environmentally benign. Various fundamental aspects of the DES-type CE media were investigated, including thermal property, viscosity, electroconductivity, Joule heating effect, and compatibility with detectors. A simulated complex mixture of ten naphthalene-based compounds with varied charges and sizes was separated using the DES-based medium in capillary zone electrophoresis (CZE) mode. Moreover, we also established a DES-based micellar electrokinetic chromatography (MEKC) system utilizing Tween-20 as the surfactant. Six structurally similar naphthalene derivatives (isomers) that couldn't be resolved by CZE were effectively separated due to their strong hydrophobic interaction with Tween-20 micelles within the DES medium. Given that DESs are "designer" solvents with highly tunable properties and environmentally friendly characteristics, this study demonstrates the potential of employing DESs as an alternative to organic solvents for greener CE separations. [ABSTRACT FROM AUTHOR]

• The novel SUPRADES consists of sulfated-β-CD and citric acid (S-β-CD-CA). • S-β-CD-CA proved to be an efficient chiral selector in CE. • Successful enantioseparation of fluorine-substituted amphetamine analogs. In this study, a novel supramolecular deep eutectic solvent consisting of sulfated-β-CD and citric acid (S-β-CD-CA) is reported for the first time. This innovative system was evaluated as a sole chiral selector in capillary electrophoresis for the enantioseparation of six fluorine-substituted amphetamine analogs, yielding remarkable outcomes. Baseline separations of all amphetamine analogs under study were achieved in less than 21.00 min using the S-β-CD-CA as the chiral selector. It was observed that the addition of 0.050 % v/v S-β-CD-CA into the background electrolyte resulted in the baseline separation of five out of the six fluorine-substituted amphetamine analogs, while in the case of the para -substituted amphetamine analog, 4-fluoramphetamine (4-FA), a higher percentage (0.15 % v/v) was required to achieve baseline enantioseparation. These findings emphasized the potential of this new supramolecular system in providing a class of solvents with promising chiral recognition properties. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs), as non-molecular type solvents, possess excellent physical-chemical properties, which make them useful in important separation applications in gas chromatography, liquid chromatography, and capillary electrophoresis. Among a plethora of potential uses of ionic liquids in separation science, capillary electrophoresis can utilize its resolution-enhancing effect in the analysis of proteins and carbohydrates, via the formation of intermolecular interactions, e.g., hydrophobic, hydrogen bonding, or electrostatic. ILs and polymeric ionic liquids (PIL) also represent an excellent choice as background electrolyte (BGE) additives for capillary coatings in CE, which is especially important in protein analysis. Another interesting utilization of ILs is the fabrication of monoliths for capillary electrochromatography in which instance the mechanism of retention is based on ion exclusion interactions. Carbohydrates can also be readily analyzed by CE with the help of ionic liquids without the need for an extra derivatization step. One of the future perspectives on the use of ILs is their utilization in the recently emerging biopharmaceutical industry exploiting the increased resolution of proteins and carbohydrates, two of the important components of glycoprotein therapeutics. In this paper, we address the so-far not-reviewed ionic liquid-mediated analysis of proteins and carbohydrates by capillary electrophoresis-based techniques also addressing their impact on the separation mechanism., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The influence of mobile phase composition on the efficiency of enantiomer separation by achiral chromatography (ACh) was investigated. The separation was induced by the phenomenon of self-disproportionation of enantiomers (SDE) triggered by their homo and hetero-chiral interactions in an achiral environment. Typically, SDE occurs in apolar mobile phases of weak elution strength, which causes the separation time to extend and the process productivity to deteriorate. To mitigate that effect, we altered the content of a strong solvent (modifier) in the mobile phase by use of a solvent gradient in which the target enantiomer was separated in the presence of the weak solvent, whereas the unresolved mixture of enantiomers was eluted by increasing the modifier content in the mobile phase. This enabled accelerating the solute elution while preserving the separation selectivity. The approach was examined for the separation of nonracemic mixtures of two structurally different compounds that exhibited the SDE effect in ACh, i.e., metalaxyl (MX) and methyl p-tolyl sulfoxide (MTSO). The target compound of the separation was the more abundant enantiomer in the enantiomeric mixture. The process realization was preceded by the determination of the effect of the modifier content on the separation yield for enantiomeric mixtures of MX and MTSO of different enantiomeric excess (ee). In the case of MX, yield of the pure target enantiomer varied from 2 %, for the maximum concentration of the modifier, to 45 % for the minimum modifier concentration and the largest ee used in the experiments. In the case of MTSO, the yield varied from minimum 40 % to maximum 66 %. To predict the process, we employed a dynamic model, in which underlying thermodynamic dependencies were implemented., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Trace substances in surface waters may threaten health and pose a risk for the aquatic environment. Moreover, separation and detection by instrumental analysis is challenging due to the low concentration and the wide range of polarities. Separation of polar and nonpolar analytes can be achieved by using stationary phases with different selectivity. Lower limits of detection of trace substances can be obtained by offline enrichment on solid phase materials. However, these practices require substantial effort and are time consuming and costly. Therefore, in this study, a column switching was developed to enrich and separate both polar and nonpolar analytes by an on-column large volume injection of aqueous samples. The column switching can significantly reduce the effort and time for analyzing trace substances without compromising on separation and detection. A reversed phase (RP) column is used to trap the nonpolar analytes. The polar analytes are enriched on a porous graphitized carbon column (PGC) coupled serially behind the RP column. A novel valve switching system is implemented to enable elution of the nonpolar analytes from the RP column and, subsequently, elution of polar analytes from the PGC column and separation on a hydrophilic interaction liquid chromatography (HILIC) column. To enable separation of polar analytes dissolved in an aqueous matrix by HILIC, the water plug that is flushed from the PGC column is diluted by dosing organic solvent directly upstream of the HILIC column. The developed method was tested by applying target analysis and non-target screening, highlighting the advantage to effectively separate and detect both polar and nonpolar compounds in a single chromatographic run. In the target analysis, the analytes, with a logD at pH 3 ranging from -2.8 to + 4.5, could be enriched and separated. Besides the 965 features in the RP phase, 572 features from real wastewater were observed in the HILIC phase which would otherwise elute in the void time in conventional one-dimensional RP methods., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this study, a molecularly imprinted polymer (MIP)-based extraction process for determining curcumin in food samples was carried out. MIP and NIP were thermally synthesized in acetonitrile solvent (porogen) using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linking agent, azobisisobutyronitrile as an initiator, and curcumin as a template molecule. Parameters affecting the synthesis process, such as temperature, the ratio of the components in the reaction, and the extraction solvent, were investigated. The characteristics of the synthesized material were examined using infrared spectroscopy and scanning electron microscopy. The maximum adsorption capacity of the material was found to be 1.34 mg/g MIP with an adsorption efficiency of 89.96% for MIP and 12.35% for NIP. The MIP material exhibited high selectivity for curcumin compared to other compounds such as quercetin (18.00%), rutin (14.74%), and ketoconazole (0.00%). The analysis method for curcumin using the MIP material was performed with validated parameters including linear range (1 - 25 mg/L, r 2  = 0.9997), accuracy (recovery rate of 90.90 %), precision (RSD R  = 0.338 %, RSDr = 1.591 %), detection limit (0.051 mg/L), and quantification limit (0.156 mg/L). The validation results indicated that the HPLC-DAD method was entirely suitable for analyzing the curcumin content in food samples., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Van-Trong Nguyen reports financial support and equipment, drugs, or supplies were provided by Industrial University of Ho Chi Minh City., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Here, we report the preparation and application of two new chiral monoliths for the enantioseparation of chiral drugs in nano-LC. Using 3‑chloro-2-hydroxypropylmethacrylate (HPMA-Cl, 2) as a precursor monomer, two different chiral monomers namely, N α -Boc-Lys-HPMA (3A) and N α -Fmoc-Lys-HPMA (3B) were synthesized and used for the preparation of chiral polymer monoliths. The first monolithic column (referred to as monolith I) was prepared by an in-situ polymerization of N α -Boc-Lys-HPMA as the chiral monomer and ethylene dimethacrylate while the second monolithic column (referred to as monolith II) was prepared by an in-situ polymerization of N α -Fmoc-Lys-HPMA as the chiral monomer and ethylene dimethacrylate as the crosslinker. Methanol and 1-propanol were used as the porogenic solvents. The prepared chiral monoliths were investigated for the enantioseparation of chiral drugs, including β-blockers (e.g., atenolol, propranolol, metoprolol) and anti-inflammatory drugs (e.g., ketoprofen, ibuprofen, flurbiprofen, naproxen, etodolac). The enantioseparation could be achieved via the formation of π-π interactions on the aromate-rich and aromate-poor chiral molecules while enantioseparation mechanism of chiral drugs included mostly π-π interactions and hydrogen bonding. Monolith II showed better enantioselectivity than Monolith I and the resolution values up to 2.12 were successfully achieved., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A detailed analysis of intra-particle volumes and layer thicknesses and their effect on the diffusion of solutes in hydrophilic interaction liquid chromatography (HILIC) was made. Pycnometric measurements and the retention volume of deuterated mobile phase constituents (water and acetonitrile) were used to estimate the void volume inside the column, including not only the volume of the mobile phase but also part of the enriched water solvent acting as the stationary phase in HILIC. The mobile phase (hold-up) volume accessible to non-retained components was estimated using a homologous series approach. The joint analysis of the different approaches indicated the formation of enriched water layers on the hydrophobic silica mesopore walls with a thickness varying significantly with mobile phase composition. The maximal thickness of the enriched water layers, which corresponded to the minimum void volume accessible to unretained solutes, marked a transition in the retention behavior of the studied analytes. Discrepancies between deuterated solvent measurements and pycnometry were explained by the existence of an irreplaceable water layer adsorbed on the silica surface. Regarding the diffusion behavior in HILIC, peak parking experiments were used to interpret the influence of the acetonitrile content on the effective diffusion coefficient D eff . A systematic decrease in D eff and molecular diffusion D m was observed with decreasing acetonitrile concentration, primarily attributed to variations in mobile phase viscosity. Notably, D eff /D m remained nearly unaffected by variations in mobile phase composition. Finally, the effective medium theory was used to make a comprehensive analysis of D part /D m to study the contribution to band broadening when the solute resides in the mesopores. The obtained data unveiled a curvature with a minimum corresponding to conditions of maximum water-layer thickness and retention. For the weakly retained compounds (k' < 0.5) the D part /D m -values were found to be relatively high (order of 0.35-0.5), which directly reflects the high γ s D s /D m -values that were observed (order 0.35-7)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Highlights • Solvent properties of aqueous Dex-PEG and PEG-Na 2 SO 4 ATPS examined. • Effects of NaCl and NaClO 4 on the properties of Dex-PEG and PEG-Na 2 SO 4 ATPS compared. • With each salt additive different osmolytes additives were used. • Effects of additives on partitioning of organic compounds and proteins studied. • Partition coefficients ranges in the systems compared. Abstract Effects of two salt additives, NaCl and NaClO 4 , at the fixed concentrations of 0.215 M on the properties of aqueous two-phase systems (ATPSs) formed by dextran (Dex) and polyethylene glycol (PEG), and the effects of NaClO 4 at the same concentration on the properties of ATPS formed by PEG and Na 2 SO 4 were examined. The effects of these salt additives on partitioning of 12 small organic compounds and five proteins in the above ATPSs were studied. In each system with a given salt additive, 0.5 M sorbitol, 0.5 M sucrose, and 0.5 M and 1.5 M trimethylamine N-oxide (TMAO) were also used as additives. The results obtained were compared with those reported previously for the Dex-PEG ATPS without salt additives and PEG-Na 2 SO 4 ATPS without salt additives and in the presence of 0.215 M NaCl. It is shown that the differences between the solvent properties of the phases in the systems formed by polymer and salt exceed those observed in the systems formed by two polymers. The three most significant solvent features of the systems are hydrophobic and electrostatic properties and hydrogen bonding donor acidity of the solvent media. Osmolyte additives were found to have a significant effect on the differences between the electrostatic properties of the phases. Analysis of the partition coefficients of 12 organic compounds and five proteins showed that the osmolyte additives may affect the partition behavior of compounds in a compound-specific manner. The relative contributions of different types of interactions of a given compound with aqueous media change in the presence of salt and osmolyte additives. Analysis of the variability ranges of partition coefficient, K , in the systems studied showed that for small organic compounds, the ranges of K -values observed in the PEG-Na 2 SO 4 ATPSs exceed those determined in the Dex-PEG ATPSs quite significantly, whereas for proteins, the range of K -values in Dex-PEG ATPSs exceeded those in PEG-Na 2 SO 4 ATPSs for three proteins, and were very similar for two proteins. This observation supported the notion that the ATPSs formed by two polymers are more suitable for protein analysis than those formed by a single polymer and a salt. The single polymer-salt ATPSs have an advantage for protein isolation/separation. [ABSTRACT FROM AUTHOR]

Highlights • A new bio-compatible deep eutectic solvent was introduced. • ChCl:Ph-ETOH proceeded amphetamine-type stimulants microextraction properly. • Facile synthesis alongside emulsifier-less microextraction is impressive. • Analyses of therapeutic/potentially toxic domains were successfully practicable. Abstract In this study, a new extraction medium based on a quite bio-compatible and bio-degradable deep eutectic solvent comprising choline chloride and phenylethanol (ChCl: Ph-ETOH) was simply and cheaply synthesized at room temperature. At the next step, it was effectively utilized at the service of air agitated-emulsification microextraction (AA-EME) of two major amphetamine-type stimulants (ATSs) in human plasma and pharmaceutical wastewater pursued by high performance liquid chromatography-ultraviolet detection (HPLC-UV). This safe, effective, and rapid enrichment process based on the new low-density DES was easily practicable via a homemade extraction cell possessing a narrow neck and with no extra demand the emulsifier intermediates. Statistical study of main parameters effects using central composite design (CCD) combined with desirability function (DF) demonstrated that pH 12, 250 μL of extraction solvent, 8 air agitation cycles, and 5% of salt amount resulted in maximum extraction efficiencies (63–66%) with DF value close to 0.98. Under optimal conditions, wide linear dynamic ranges (LDRs) of 15.0–2000 and 8.0–3000 ng mL−1 with the determination coefficients (R2s) close to 0.99 were obtainable for amphetamine and methamphetamine, respectively. Low limits of detection (LODs) as well as relative standard deviations (%RSDs, n = 3) were found to be 2.0–5.0 ng mL−1 and 5.7–7.8%, respectively. Also, enrichment factors (EFs) were quantitative in the span of 47–50. On the other hand, satisfactory and accurate assessment at low levels close to therapeutic and toxic domains in human plasma sample and pharmaceutical wastewater was successfully obtained. [ABSTRACT FROM AUTHOR]

Highlights • Flexible eluent dosage onto the surface of the adsorbent layer by moving pipette. • 3D machine is used to drive pipette for eluent delivery. • Planar chromatogram is developed with controlled velocity of the mobile phase. • The equipment enables determination of the plate height vs. solvent flow velocity. Abstract The new approach to the development of thin-layer chromatograms is presented. For the first time we show flexible mobile phase dosage onto the surface of the adsorbent layer by moving pipette combined with precise syringe pumps. The pipette is driven into movement by computer controlled 3D machine (modified 3D printer mechanism). Delivery of the mobile phase to the adsorbent layer is equal to or lower than that of conventional development. Therefore chromatograms can be developed with optimal mobile phase velocity, adjusted to its absorption rate by the adsorbent layer. Under such conditions there is no excess of eluent on the surface of the adsorbent layer so higher performance of the chromatographic system can be obtained. Moreover chromatograms can be developed with constant linear mobile phase velocity and therefore the relationships the plate height vs. mobile phase linear velocity obtained with planar chromatography driven by capillary forces are investigated and reported. In addition the contribution of starting spot variance in total peak variance and the influence of narrowing of starting spots on performance of the chromatographic system have been studied. The results confirm a very significant starting spot variance contribution to total peak variance and consequently considerable influence of starting spot size on plate height of the separation system, when chromatogram is developed on a short distance. In the paper the advantages and disadvantages of the prototype device and its possible application are discussed. [ABSTRACT FROM AUTHOR]

Highlights • New, nonionic, hydrophobic deep eutectic solvents (DES) composed of natural compounds • Inexpensive, nontoxic DES were used as an extracting solvent • Green sample preparation method • Easy and sensitive method for monitoring PAHs during wastewater treatment processes Abstract The paper presents novel nonionic and hydrophobic deep eutectic solvents which were synthesized from natural compounds, i.e., thymol, ±camphor, decanoic and 10-undecylenic acids. Fundamental physicochemical properties of the synthesized deep eutectic solvents were determined, followed by their application as extractants in ultrasound-assisted dispersive liquid-liquid microextraction to isolate and enrich polycyclic aromatic hydrocarbons from aqueous samples characterized by a complex matrix. The final determination was carried out by gas chromatography-mass spectrometry. The most important extraction parameters were optimized and the procedure was validated. The developed procedure is characterized by low limits of detection and quantitation, equal to 0.0039–0.0098 μg/L and 0.012–0.029 μg/L, respectively, good precision (RSD <6.09%), analyte recovery ranging from 73.5 to 126.2%, and a wide linear range. The procedure was applied to analysis of industrial effluents from the production of bitumens before and after treatment by advanced oxidation processes. A total of 16 PAHs at concentrations ranging from 0.12 to 46.2 μg/L were identified and determined. [ABSTRACT FROM AUTHOR]

A pseudo simulated moving bed (SMB) with solvent gradient was used to trap and separate paclitaxel from yew extracum. This SMB process consisted of three steps: feeding, purification and recovery. In comparison with methanol/water as an eluent, acetonitrile/water could give a better separation but had a poor dissolubility of the yew extracum, and therefore methanol/water was used in the feeding followed by acetonitrile/water in the purification. In the first two steps, water was deliberately added into zone III to modulate the eluotropic strength of the liquid entering zone III, so as to make paclitaxel separation from impurities be more efficient. Once most of impurities discarded, the columns were in turn eluted to recover the trapped paclitaxel of 98% yield with a purity of 78% from the yew extracum containing 1.5% paclitaxel. Afterward, an additional operation of crystallization improved the purity further to 97.8% with the yield of 95%. [ABSTRACT FROM AUTHOR]

A new methodology is presented for two-dimensional liquid chromatography (2D-LC) separations of polymers. Active solvent modulation (ASM) was evaluated in its effectiveness to enhance solvent compatibility for both separation dimensions. As an example the determination of target compounds in epoxy resins was used. Ultra-high pressure size-exclusion chromatography was applied in the first dimension using THF as the solvent. The second dimension separation was operated in reversed-phase mode using an acetonitrile/water gradient. ASM prevents sample breakthrough in the second dimension and produces chromatograms that are of great peak shape and high resolution. It enables very sensitive determination of target components down to the low ppm level. The resulting high-speed 2D-LC method (10 min analysis time) showed good linearity (R 2  > 0.9995) and reproducibility (as low as 0.3–0.7% peak area RSD). ASM was also applied in comprehensive 2D-LC (SECxLC) mode for characterization of molecular weight and chemical composition distribution of a polymer blend consisting of epoxy novolac and phenol novolac. The SECxLC separation was executed at short run times (20 min). ASM technology can markedly enhance productivity in 2D-LC analysis for many complex sample matrices. [ABSTRACT FROM AUTHOR]

Various p - tert -octylcalix[4]arene derivatives as hydrophobic extractants have been prepared to investigate Ag(I) extraction efficiency in a batch-wise process in nitric acid media. The influence of the functional groups of the hydrophobic extractants on the interfacial behavior and Ag(I) extraction efficiency in nitric acid media has been investigated using the drop-volume method. Fitting of the interfacial tension isotherms to the Gibbs and Szyszkowski equations has provided parameters characterizing the interfacial activity of the extractants, in particular the Gibbs free energy of adsorption at the interface, the interface excess on saturation (Г ∞ ) and the average area per the adsorbed extractant molecule ( A min ). The amido-type p - tert -octylcalix[4]arene derivatives have strong interfacial activity and fast extraction rates. The interface excess at saturation (Г ∞ ) increased with the type of functional groups in the following order: methyl ketonic < phenyl ketonic < dibenzyl amido < diethyl amido < quinolyl < pyridyl. The relationship between the interfacial activity and the dependence of the Ag(I) extraction efficiency on the different functional groups is discussed. The interfacial behavior of the extractants affected both the solvent extraction equilibrium and the kinetics and the overall results are consistent with a mass transfer mechanism at the heterogeneous liquid-liquid interfaces. [ABSTRACT FROM AUTHOR]

The mobile phase, when used in combination with a polysaccharide-based sorbent, often contains hydrocarbons with polar modifiers. Studies have investigated the effect of solvent on the recognition mechanism of polysaccharide-based sorbents, but it remains unclear how these modifier molecules affect solute retention behavior. This study used an amylose 3,5-dichlorophenylcarbamate–based sorbent to systematically investigate the retention behavior of various solutes as a function of the concentration of four polar modifiers: ethanol, isopropanol, methyl tert -butyl ether, and acetone. The thermodynamic properties of adsorption for the four modifiers were thoroughly investigated using retention factor data, van’t Hoff plots, and adsorption isotherms of the modifier molecules. The adsorption data of acetone and isopropanol followed the Langmuir isotherm, whereas the bi-Langmuir isotherm more accurately fit the ethanol data. For methyl tert -butyl ether, the Brunauer–Emmett–Teller adsorption isotherm indicated multilayer adsorption with a low saturation capacity of the first adsorption layer. A multivalent retention model interpreted slopes of the plots of the logarithm of the retention factor versus the logarithm of the modifier concentration. Because the molecular polarity of acetone is stronger than that of methyl tert -butyl ether, the limiting absolute slope values of tetrahydrofuran at a very high acetone modifier concentration were smaller than that when methyl tert -butyl ether was used as the polar modifier. The higher absolute value of the slope for tert -butanol suggested the potential of C O groups of acetone molecules to form bifurcated H bonds on a tert -butanol molecule. When alcohol was employed as the polar modifier, the results suggested that the effect of isopropanol self-association on the retention factor was stronger than the effects of solute–IPA complexation and isopropanol adsorption. For alcohol modifiers, U-shaped retention curves were obtained for all aromatic solutes. When acetone or methyl tert -butyl ether was used, the absence of a U-shaped curve indicated the weak polarity of those modifiers. [ABSTRACT FROM AUTHOR]

The time taken to achieve full column equilibration for isocratic analysis of acidic, basic, and neutral solutes in hydrophilic interaction liquid chromatography (HILIC) was compared using the mobile phase disturbance method, column efficiency measurements and retention time stability. Full equilibration, which could take up to an hour, was best measured by the last procedure and was found to depend on the nature of the stationary phase, the pre-equilibrium (e.g. storage) solvent and the flow rate. While longer equilibration times are a relatively minor inconvenience in isocratic analysis, they are surprisingly not a barrier to the use of gradient elution in HILIC. A repeatable partial equilibration giving retention time stability equivalent to that in isocratic analysis was demonstrated for an equilibration time of only ∼5 min, using as few as 2 preliminary conditioning runs on a column that had taken the longest time to achieve full equilibration. Due to selectivity changes that occur dependent on the equilibration time, it is necessary to use identical gradient conditions in a series of analyses, which however appears to be facile on a modern HPLC instrument. [ABSTRACT FROM AUTHOR]

Personal care products (PCPs) are ubiquitous in aquatic environments owing to the continuous discharge of domestic wastewater from highly urbanized regions. These PCPs can be adsorbed by fish and thereafter usually enter the bile of the fish through biliary excretion. In this study, a sensitive method based on a combination of hybrid solvent precipitation and dispersive solid phase extraction (d-SPE) purification was developed to simultaneously extract and detect 24 PCPs, namely, 16 biocides, 4 synthetic musks, and 4 benzotriazoles, from fish bile. Hybrid precipitation on solid phase extraction (SPE) tubes was applied to remove phospholipids and proteins, and a d-SPE procedure was used for further purification. The extraction solvents for the hybrid precipitation/SPE tubes and d-SPE materials were optimized. The method performance for bile samples both with and without enzyme hydrolysis using β -glucuronidase/aryl-sulfatase were validated. The 24 PCPs in fish bile were spiked with standard concentrations of 10 ng/mL, 20 ng/mL, 100 ng/mL, and 200 ng/mL to evaluate recoveries, which ranged from 70 to 120% for 16, 16, 22, and 21 analytes with hydrolysis, respectively, and 70–120% for 14, 15, 23, and 23 analytes without hydrolysis, respectively. The quantification limits for target PCPs were in the range 0.26–7.38 ng/mL [excluding musk xylene (MX) and musk ketone (MK)] and 0.20–9.48 ng/mL (excluding MX and MK) for bile samples with and without enzyme hydrolysis, respectively. After enzyme hydrolysis, 12 PCPs were detected in bile from fish collected from the Yangtze River, with a maximum detected concentration of 460 ng/mL, for triclosan (TCS). The hydrolysis reaction indicated that high percentages of glucuronide and sulfate metabolites for some PCPs, i.e. four parabens and TCS, existed in the bile. [ABSTRACT FROM AUTHOR]

In the present study, a highly selective fluorous affinity-based dispersive liquid–liquid microextraction (DLLME) technique was developed for the extraction and analysis of per- and polyfluoroalkyl substances (PFASs) followed by high performance liquid chromatography tandem–mass spectrometry. Perfluoro- tert -butanol with multiple C-F bonds was chosen as the extraction solvent, which was injected into the aqueous samples with a dispersive solvent (acetonitrile) in a 120:800 (μL, v/v) mixture for PFASs enrichment. The fluorous affinity-based extraction mechanism was confirmed by the significantly higher extraction recoveries for PFASs containing multiple fluorine atoms than those for compounds with fewer or no fluorine atoms. The extraction recoveries of medium and long-chain PFASs (CF 2  > 5) exceeded 70%, except perfluoroheptanoic acid, while those of short-chain PFASs were lower than 50%, implying that the proposed DLLME may not be suitable for their extraction due to weak fluorous affinity. This highly fluoroselective DLLME technique can greatly decrease the matrix effect that occurs in mass spectrometry detection when applied to the analysis of urine samples. Under the optimum conditions, the relative recoveries of PFASs with CF 2  > 5 ranged from 80.6-121.4% for tap water, river water and urine samples spiked with concentrations of 10, 50 and 100 ng/L. The method limits of quantification for PFASs in water and urine samples were in the range of 0.6–8.7 ng/L. Furthermore, comparable concentrations of PFASs were obtained via DLLME and solid-phase extraction, confirming that the developed DLLME technique is a promising method for the extraction of PFASs in real samples. [ABSTRACT FROM AUTHOR]

• Electroosmotic coupled particle-assisted solvent flotation was designed. • The extraction rate of cinnamaldehyde was increased under low voltage of ECPASF. • Compared to conventional water distillation method, the ECPASF was efficient. • Cinnamaldehyde showed good antioxidant activity in cellular antioxidant evaluation. Cinnamaldehyde has been widely applied in various fields due to its special flavor and various pharmacological activities, such as antioxidant, anti-inflammatory and antibacterial properties. The strategy of quick and efficient enrichment for cinnamaldehyde is imperative. In this study, an electroosmotic coupled particle-assisted solvent flotation (ECPASF) system was designed for the cinnamaldehyde enrichment from cinnamon. The response surface method was used to optimize extraction parameters. Under optimal operating conditions, its yield was 9.33 ± 0.11 mg/g. Such high yield of cinnamaldehyde using the ECPASF might be because electroosmosis effectively alters the permeability of plant cells, which facilitates the release of cinnamaldehyde. In addition, both the crude extract of cinnamon and pure cinnamaldehyde showed good antioxidant activity. The results demonstrated that the ECPASF system is a sustainable and effective method for the extraction of cinnamaldehyde from cinnamon. It also has the prospect of being extended to the extraction of other natural products. [ABSTRACT FROM AUTHOR]

• Polar organic solvents yield fast and efficient enantioseparation of liquid crystals. • Chlorinated amylose-based chiral column brings the highest enantioselectivity values. • Methanol-rich mobile phases yield the best results for perfluorinated liquid crystals. • Lateral fluorination reduces enantioresolution regardless of the used mobile phase. Three sets of fluorinated chiral liquid crystals were used to explore the polar organic solvent chromatography mode for their enantioseparation. The materials include a set of newly synthesized compounds with chiral center derived from 2-hexanol and two sets of compounds with chiral center derived from 2-/3-octanol. Baseline enantioseparation of all materials was achieved using binary mobile phases without additives. For some of the compounds exceedingly high values of enantioresolution (> 20) and enantioselectivity (> 4) were found. The chromatographic behavior of the sample set was studied on three different polysaccharide-based chiral columns – Chiralpak IA-U, IG-U and IB-U. Comparison of results from Chiralpak IA-U and IB-U shows the effect of amylose vs. cellulose polysaccharide backbone while comparison of Chiralpak IA-U and IG-U reveals the effect of 3,5-dimethylphenylcarbamate vs. 3‑chloro-5-methylphenylcarbamate substituent. The mobile phases tested included whole range of acetonitrile/methanol mixtures to demonstrate that acetonitrile-rich and alcohol-rich mobile phases offer different enantiorecognition mechanisms and can provide complementarity to some extent. The effect of temperature on enantioseparation was investigated on Chiralpak IA-U by constructing van't Hoff plots for selected liquid crystals in pure acetonitrile and pure methanol as mobile phases. [ABSTRACT FROM AUTHOR]

• Retention correlation between reverse-phase CCC and HPLC was studied. • Two typical biphasic solvent systems were investigated for retention correlation. • Big difference in elution sequence was found for CCC using specific volume ratio. • High orthogonality could be obtained for the two chromatographic methods. Correlation of elution performance between reversed phase countercurrent chromatography and liquid chromatography was investigated using five selected natural components. Theoretical guidance for orthogonality of two-dimensional countercurrent chromatography and liquid chromatography was proposed. The difference in retention behavior between countercurrent chromatography and liquid chromatography was studied when the mobile phase was composed of methanol and water by measuring the partition behavior of five selected compounds in two typical biphasic solvent systems composed of n -hexane-ethyl acetate-methanol-water and chloroform-methanol-water. An orthogonal diagram between countercurrent chromatography and liquid chromatography was obtained by normalized treatment of the measured partition coefficients and capacity factors. The experimental results showed that each biphasic solvent system used for countercurrent chromatography had a high orthogonality with liquid chromatography when a specific volume ratio was used. [ABSTRACT FROM AUTHOR]

• Process design was studied for multicolumn counter-current solvent gradient purification. • The trade-off between purity and recovery was focused. • Both model protein mixture and mAb sample with charge variants were tested. • The mismatching was found between normally designed window and elution profiles. • An improved process design strategy was proposed to improve the process performances. The multicolumn counter-current solvent gradient purification (MCSGP) method has proven effective in addressing the issue of elution profile overlap for difficult-to-separate proteins, leading to improved purity and recovery. However, during the MCSGP process, the flow rate and proportion of loaded proteins undergo changes, causing a significant discrepancy between the elution profiles of batch process design and the actual MCSGP process. This mismatch negatively impacts the purity and recovery of the target protein. To address this challenge, an improved process design (reDesign) was proposed with the first-run MCSGP to mimic the actual continuous process and obtain elution profiles that closely resemble the real ones. The reDesign was demonstrated with both a model protein mixture and a sample of monoclonal antibody (mAb) with charge variants. For model protein mixture, the reDesign-based MCSGP process (reMCSGP) showed a remarkable improvement in recovery, increasing from 83.6% to 97.8% while maintaining a purity of more than 95%. For mAb sample, the recovery of reMCSGP improved significantly to 93.9%, surpassing the performance of normal MCSGP processes at a given purity level of more than 84%. In general, the new process design strategy developed in this work could generate a more representative elution profile that closely mirrors actual conditions in continuous processes, which enhances the separation performance of MCSGP. [ABSTRACT FROM AUTHOR]

The phase diagram of a new aqueous two-phase system (ATPS) formed by polyethylene glycol with molecular weight 600 (PEG-600) and trimethylamine N-oxide (TMAO) in 0.01 M sodium phosphate buffer (NaPB), pH 7.4, is determined and hydrophobic, electrostatic and other solvent properties of the phases are characterized. The same properties are determined for the ATPS formed by PEG-600 and choline chloride in 0.01 M sodium phosphate buffer (NaPB), pH 7.4. Solvent properties of water (dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) in aqueous solutions of polypropylene glycol-400 (PPG-400), polyethylene glycol dimethyl ether -250 (PEGDME-250), and choline chloride are determined at different concentrations. The concentrations of the aforementioned polymers, as well as PEG-600 and PEG-1000 required for phase separation in mixtures with choline chloride reported in the literature are analyzed. It is found that the concentrations of polymers needed for phase separation in mixtures with 35%wt. choline chloride are linearly related with water hydrogen bond donor acidity or hydrogen bond acceptor basicity in the individual polymer solutions at given concentrations. Partition behavior of nine proteins was examined in both systems. The partition coefficients of proteins in PEG-600-choline chloride ATPS exceeded those observed in PEG-600-TMAO ATPS from ca. 2 to ca. 75-fold possibly due to the larger difference between the composition of the coexisting phases in the former ATPS. Analysis of partition coefficients in the two ATPS were compared to those reported in Dextran-PEG ATPS, and proteins likely engaged in direct interactions with choline chloride were identified. [ABSTRACT FROM AUTHOR]

Natural deep eutectic solvents (NADES) made mainly with abundant primary metabolites are being increasingly applied in green chemistry. The advantages of NADES as green solvents have led to their use in novel green products for the food, cosmetics and pharma markets. However, one of the main difficulties encountered in the development of novel products and their quality control arises from their low vapour pressure and high viscosity. These features create the need for the development of new analytical methods suited to this type of sample. In this study, such a method was developed and applied to analyse the efficiency of a diverse set of NADES for the extraction of compounds of interest from two model plants, Ginkgo biloba and Panax ginseng . The method uses high-performance thin-layer chromatography (HPTLC) coupled with multivariate data analysis (MVDA). It was successfully applied to the comparative quali- and quantitative analysis of very chemically diverse metabolites (e.g., phenolics, terpenoids, phenolic acids and saponins) that are present in the extracts obtained from the plants using six different NADES. The composition of each NADES was a combination of two or three compounds mixed in defined molar ratios; malic acid-choline chloride (1:1), malic acid-glucose (1:1), choline chloride-glucose (5:2), malic acid-proline (1:1), glucose-fructose-sucrose (1:1:1) and glycerol-proline-sucrose (9:4:1). Of these mixtures, malic acid-choline chloride (1:1) and glycerol-proline-sucrose (1:1:1) for G. biloba leaves, and malic acid-choline chloride (1:1) and malic acid-glucose (1:1) for P. ginseng leaves and stems showed the highest yields of the target compounds. Interestingly, none of the NADES extracted ginkgolic acids as much as the conventional organic solvents. As these compounds are considered to be toxic, the fact that these NADES produce virtually ginkgolic acid-free extracts is extremely useful. The effect of adding different volumes of water to the most efficient NADES was also evaluated and the results revealed that there is a great influence exerted by the water content, with maximum yields of ginkgolides, phenolics and ginsenosides being obtained with approximately 20% water (w/w). [ABSTRACT FROM AUTHOR]

Chiral separation has been a remarkably active area of research over the past long time and it still stays that way. Over the last few decades, counter-current chromatography (CCC) was successfully applied to the field of chiral separation. It provides an attractive approach to obtain pure enantiomer, particularly in preparative application because of its unique advantages of high load capacity, low solvent consumption and easy scale-up. The last several years great strides have been made in chiral separation by CCC, ranging from novel elution modes such as recycling elution mode and multiple dual mode elution to more specialized approaches such as pH-zone-refining and biphasic chiral recognition technologies. These developments have greatly improved the resolution of enantiomers and promoted the application of CCC in the field of chiral separation. Although not as popular as its application to the field of separation of natural product, the development of chiral separation by CCC should not be underrated. In this review article, we refer to the development, applications and future outlook of chiral separation by CCC, with emphasis on topics of its history, mechanism, advantages, limitations, current development and challenges. Meanwhile, its orientation of continued evolution and future outlook also have been discussed. While some scientific and technological problems have not yet been solved thoroughly, chiral separation by CCC has demonstrated potential advantages and prospects in this field and has good chance at preparative enantioseparation. [ABSTRACT FROM AUTHOR]

Typically, a target compound is selected as a template for a molecularly imprinted polymer (MIP); however, some target compounds are not suitable as templates because of their poor solubility. Using the tailoring properties of a deep eutectic solvent (DES), the insoluble target compound caffeic acid was transformed into a ternary choline chloride–caffeic acid–ethylene glycol (ChCl–CA–EG) DES, which was then employed as a template to prepare MIPs. The ternary DES-based MIPs were characterized by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy, and atomic force microscopy. The effects of time, temperature, ionic strength, and pH on the recognition processes for four polyphenols (caffeic acid, protocatechuic acid, catechin, and epicatechin) by 13 ChCl–CA–EG ternary DES-based MIPs was investigated using high-performance liquid chromatography. The recognition specificity of the MIPs for CA was significantly better than that for the other polyphenols, and the MIPs exhibited obvious characteristics of chromatographic packing materials. In addition, the recognition processes mainly followed a second-order kinetics model and the Freundlich isotherm model, which together indicated that the MIPs mainly recognized the polyphenols by chemical interactions including ion exchange, electron exchange, and new bond formation. Furthermore, the specific recognition ability of the MIPs for polyphenols, which was better than those of C 18 , C 8 , or non-molecularly imprinted polymer adsorbents, was successfully applied to the recognition of polyphenols in a Radix asteris sample. The transformation of an insoluble target compound in a polymeric DES for MIP preparation and recognition is a novel and feasible strategy suitable for use in further MIP research developments. [ABSTRACT FROM AUTHOR]

Fat-soluble vitamins and antioxidants are of relevance in health and disease. Current methods to extract these compounds from biological fluids mainly need use of multi-steps and multi organic solvents. They are time-consuming and difficult to apply to treat simultaneously large sample number. We here describe a single-step, one solvent extraction of fat-soluble vitamins and antioxidants from biological fluids, and the chromatographic separation of all-trans -retinoic acid, 25-hydroxycholecalciferol, all-trans -retinol, astaxanthin, lutein, zeaxanthin, trans -β-apo-8′-carotenal, γ-tocopherol, β-cryptoxanthin, α-tocopherol, phylloquinone, lycopene, α-carotene, β-carotene and coenzyme Q 10 . Extraction is obtained by adding one volume of biological fluid to two acetonitrile volumes, vortexing for 60 s and incubating for 60 min at 37 °C under agitation. HPLC separation occurs in 30 min using Hypersil C18, 100 × 4.6 mm, 5 μm particle size column, gradient from 70% methanol + 30% H 2 O to 100% acetonitrile, flow rate of 1.0 ml/min and 37 °C column temperature. Compounds are revealed using highly sensitive UV-VIS diode array detector. The HPLC method suitability was assessed in terms of sensitivity, reproducibility and recovery. Using the present extraction and chromatographic conditions we obtained values of the fat-soluble vitamins and antioxidants in serum from 50 healthy controls similar to those found in literature. Additionally, the profile of these compounds was also measured in seminal plasma from 20 healthy fertile donors. Results indicate that this simple, rapid and low cost sample processing is suitable to extract fat-soluble vitamins and antioxidants from biological fluids and can be applied in clinical and nutritional studies. [ABSTRACT FROM AUTHOR]

A database of partition constants for more than 300 compounds of industrial, environmental and biological interest in nineteen totally organic biphasic systems is reported. The biphasic systems consist of the polar organic solvents acetonitrile, methanol, N,N -dimethylformamide, dimethyl sulfoxide, formamide, propylene carbonate, ethylene glycol, ethanolamine and 3,3,3-trifluoroethanol with n -heptane or n -hexane (10 systems), isopentyl ether (5 systems), 1,2-dichloroethane (2 systems) and 1-octanol (2 systems) of suitable low mutual solubility. The solvation parameter model is used to identify compounds with extreme partition constant values and to develop a selection guide based on the cluster analysis of the model system constants to identify biphasic systems for liquid–liquid extraction. [ABSTRACT FROM AUTHOR]

Van’t Hoff plots have been widely used for investigating the thermodynamic properties of adsorption processes in various chromatography systems. By measuring the retention factor k over a certain temperature range, the plot of ln k versus 1/ T often yields a straight line with a slope of − Δ H vH 0 / R . Although this method provides information on adsorption enthalpy changes, its theoretical basis does not account for the effect of the solvent. In this paper, the relationship between apparent enthalpy changes determined directly from van’t Hoff plots and solvent modifier concentrations is systematically investigated using three simple solutes—tetrahydrofuran, acetone, and tert -butanol—in an n -hexane-methyl tert -butyl ether (MTBE) mobile phase with an amylose 3,5-dichlorophenylcarbamate–based sorbent. The apparent enthalpy changes of solutes are strongly dependent on MTBE concentration, increasing rapidly with MTBE content at low concentrations but leveling off after Δ H 0 reaches approximately −15 kJ/mol. These data cannot be explained by the thermodynamic model currently used in the literature. A new three-equilibrium-constant thermodynamic model is developed herein to account for solute–sorbent, solvent–sorbent, and solute–solvent interactions. The thermodynamic parameters of the model are estimated from the apparent enthalpy changes at different MTBE concentrations. The results reveal that two key dimensionless groups control the van’t Hoff enthalpic curves: the fractions of solute molecules bound to modifier molecules and adsorption sites occupied by modifier molecules. As a result, the shapes of van’t Hoff enthalpic curves reflect the adsorption isotherm of MTBE without complexation or information regarding solute–MTBE complexation without MTBE competitive adsorption. The new model is thus demonstrated to be more reliable than the current model for examining the thermodynamic properties of retention mechanisms. [ABSTRACT FROM AUTHOR]

An extraction and determination method is shown for the analysis of dyes and solvents present in two types of ballpoint pen inks that are deposited onto paper. Ink extracts are analysed using a combination of gas chromatography with mass spectrometry (GC–MS), and high-pressure liquid chromatography with photodiode array detection (HPLC-DAD), within a single sample extraction procedure. Seventeen solvents and thirteen dyes contained in two Montblanc ® inks (black and blue) were monitored for 45 months at monthly intervals, in order to determine variations in the concentrations of the compounds over time. We also studied the relative variations between different compounds and the generation of degradation products such as phenol. The concentration data obtained from these compounds during their exposure have been analysed and a multiple regression model is developed for each ink type that allows an estimate of the exposure time of the ink on paper with a maximum error of between 4 and 7 months. [ABSTRACT FROM AUTHOR]

A new in-line method of magnetic nanoparticles (MNPs) coupled with high-speed countercurrent chromatography (HSCCC) using a same solvent system during the whole separation process was established to achieve the rapid separation of flavonoids from Mikania micrantha . The adsorption and desorption capacities of five different MNPs for flavonoid standards and Mikania micrantha crude extract were compared and the most suitable magnetic nanoparticle Fe 3 O 4 @SiO 2 @DIH@EMIMLpro was selected as the in-line MNP column. An in-line separation system was established by combining this MNP column with HSCCC through a six-way valve. The comparison between two solvent systems n-hexane-ethyl acetate-methanol-water (3:5:3:5, v/v) and ethyl acetate-methanol-water (25:1:25, v/v) showed that the latter solvent system was more suitable for simultaneously in-line separating three flavonoids quercetin-3-O-rutinoside, luteoloside and astragalin from Mikania micrantha . The purities of these three compounds with the ethyl acetate-methanol-water solvent system were 95.13%, 98.54% and 98.19% respectively. Results showed the established in-line separation system of MNP-HSCCC was efficient, recyclable and served to isolate potential flavonoids with similar polarities from natural complex mixtures. The in-line combination of magnetic nanoparticles with high-speed countercurrent chromatography eluting with the same solvent system during the whole separation process was established for the first time. [ABSTRACT FROM AUTHOR]

In this work, thermal desorption-gas chromatography-flame ionization detection (TD-GC-FID) was adapted to enable the determination of residual solvents (RS) in mesoporous silica (MPSi). MPSi is often utilized in various pharmaceutical formulations or drug delivery systems and the accurate determination of RS is an important part of pharmaceutical quality control. Seven commonly used solvents (methanol, ethanol, acetone, isopropanol, dichloromethane, tetrahydrofuran and hexafluoroisopropanol) were evaluated in combination with 3 types of MPSi having pore sizes of 2–3, 15 and 25 nm. Validation results showed general recovery values > 98% and good linearity over the concentration ranges studied. The limits of detection (LOD) and limits of quantification (LOQ) for the different solvents ranged from 0.03 to 0.08 μg and from 0.1 to 0.2 μg per tube, respectively. Verification of the accuracy of the TD method was investigated by using an alternative method based on complete dissolution of MPSi in hydrofluoric acid (HF) followed by full evaporation headspace-GC (HS-GC). The results obtained from both procedures were not statistically different (p > 0.05) when applied to actual experimental drug samples consisting of itraconazole loaded on MPSi. [ABSTRACT FROM AUTHOR]