查看更多>>摘要：? 2022In this study, the impact of introducing water in the sample solvent upon the injection in SFC is investigated. Adsorption of water on the stationary phase was indicated. Using a set of ten neutral test compounds and four ionizable test compounds, spread all along the co-solvent gradient, several parameters were scrutinized (i.e. water content in the sample diluent, nature of the sample diluent, nature of the co-solvent) in regards to peak broadening. From this systematic investigation, the competition for adsorption on the stationary phase between the analytes and the water molecules contained in the diluent was highlighted. The chromatographic peaks of neutral molecules eluting before water molecules were compressed and the ones eluting after were broadened. While the extent of this phenomenon was related to the peak position for neutral molecules, it was not observed on acidic molecules.
查看更多>>摘要：? 2022The development of novel stationary phases to achieve high-efficiency separation is still an important topic in separation sciences. Covalent organic frameworks (COFs) with the advantages of large specific surface areas, high porosity and stability have attracted great attention in chromatographic field. Here, a novel crystalline covalent organic framework (TzDa-V) was designed and synthesized by condensation reaction between 4,4′,4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (Tz) and 2,5-diallyloxyterephthalaldehyde (Da-V) for open-tubular capillary electrochromatography (OT-CEC). Thanks to the regular shape, strong hydrophobicity and microporous structure of COF TzDa-V, the TzDa-V modified capillary column exhibited excellent efficiency for the separation of several groups of small molecules, including alkylbenzenes, chlorobenzenes, sulfonamides and so on. The maximum column efficiency can reach about 2.0 × 105 plates?m?1 (for chlorobenzene). Besides, the prepared COF TzDa-V modified OT-column can afford methylbenzene loading capacity of 127.72 pmol. Also, the OT-columns were considerably stable and reproducible. The RSDs of intra-day (n = 3), inter-day (n = 3) and three batches runs for the retention times of four benzenes were all below 1.89%. Our successful work indicates the great potential of COF TzDa-V in CEC for high-efficiency separation.
查看更多>>摘要：? 2022 Elsevier B.V.The research of the use of steroid compounds in the treatment of various types of cancer has a history of more than 50 years. Numerous steroid derivatives have expressed significant anticancer activity, however the thorough analysis of their physicochemical and toxicological properties is required prior to their clinical application. The present study is focused on the characterization of physicochemical properties of a series of previously synthesized new androstane derivatives (16E-hydroxyimino derivatives, D-homo lactones and D-seco dinitriles) with anticancer activity applying reversed-phase ultra high performance liquid chromatography (RP-UHPLC) system under isocratic conditions and chemometric tools, including in silico determination of their absorption, distribution, metabolism, excretion and toxicity (ADMET) properties. The chromatographic analysis was carried out applying two two-component and one ternary mobile phases with aprotic (acetonitrile) and protic (water and methanol) solvents. The conducted quantitative structure-retention relationship modeling resulted in two univariate and nine multivariate linear mathematical models that successfully correlate the retention parameters (logk) with descriptors of molecular polarity/lipophilicity (tPSA, REF, Average LogP, ClogP, ALOGP, LogS-SILICOS-IT, AClogS), descriptors that mainly depend on intermolecular interactions (BP, CP, CT, DE, HL) and ADMET descriptors (SWISSLogKpSP, GPCR, HIA, EI). The quality of the models was proved by the internal and external validation, while the robustness of the models was confirmed by Y-randomization test. Considering the established meaningful relationships between physicochemical/ADMET properties and retention parameters, the determined logk parameters of the analyzed series of steroid derivatives can be considered to be a biopharmaceutical property from the perspective of lipophilicity.
查看更多>>摘要：? 2022 Elsevier B.V.Taylor-Aris dispersion represents an undesired phenomenon in pressure-driven liquid chromatography, often responsible for the unchecked increase of the Height Equivalent of the Theoretical Plate (HETP) when high throughput operating conditions are sought. Previous work on the subject showed how it is possible to contain the augmented dispersion in empty microchannels by inducing cross-sectional velocity components yielding an overall helical structure of the flow streamlines. Here, we explore the possibility of further reducing axial dispersion by devising flow conditions that give rise to chaotic streamlines. A three-dimensional steady flow generated by the combination of a pressure-driven Poiseuille flow and an electroosmotically-induced spatially periodic flow is used as a case study. Brenner's macrotransport approach is used to predict the axial dispersion coefficient of a diffusing solute in flows possessing regular, partially chaotic and globally chaotic kinematic features. Accurate Lagrangian-stochastic simulations of particle ensembles are used to validate the predictions obtained through Brenner's paradigm. Our findings suggest that the Taylor-Aris phenomenon can be altogether suppressed in the limit of globally chaotic kinematics. A theoretical interpretation of this outcome is developed by combining macrotransport theory with established results of the spectral approach to mixing in advecting-diffusing chaotic flows.
查看更多>>摘要：? 2022A rapid reversed-phase high performance liquid chromatographic (HPLC) methodology for chiral separation of three profen compounds has been developed and then applied to enantiomeric impurity testing of their corresponding enantiopure drugs. The assay is specific, allowing quantitation of the enantiomeric impurities at levels of 0.0078%, 0.0105%, and 0.0416% relative to S-ibuprofen, S-naproxen, and S-ketoprofen, respectively. In order to gain a better insight into the chiral recognition mechanisms of chiral profens on an FLM Chiral NQ(2)-RH column, molecular docking studies were carried out using AutoDock 4.0 software. It was found that hydrogen bonding, hydrophobic interactions, and π-π stacking were all involved in stereoselective interactions, and the calculated binding energy (BE) obtained reflected the binding strength of each enantiomer interacting with a chiral selector. The higher the BE value, the harder it was to elute the corresponding enantiomer, which also accorded with the enantiomer elution order observed in the actual enantiomeric separation. Additionally, thermodynamic analysis revealed that the enantioseparation process at 15–40°C was driven mainly by entropic contributions. The methodology was further validated according to the International Council for Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guideline Q2 (R1) and proved to be sensitive, linear, precise, and accurate for determining R-profen impurities in three commercially available single-enantiomer S-profen drugs. As expected, in the case of products acquired in actual pharmacies, the levels of all of the monitored impurities were found to be lower than the allowable impurity limits.
查看更多>>摘要：? 2022 Elsevier B.V.Catechin and epicatechin were enantioseparated by high-performance liquid chromatography (HPLC) with a phenyl column and aqueous mobile phases containing 0.05% (w/v) and 0.6% (w/v) of β-cyclodextrin for catechin and epicatechin, respectively. β-Cyclodextrin was found to be scarcely retained on a phenyl column. Consequently, it was suggested that catechin, which was eluted earlier than epicatechin, formed more stable inclusion complex with β-cyclodextrin than epicatechin and earlier eluted enantiomers, (?)-catechin and (+)-epicatechin, formed more stable diastereomer complexes with β-cyclodextrin than the respective enantiomers. This was confirmed by β-cyclodextrin-modified micellar electrokinetic chromatography and Benesi?Hildebrand plots by fluorescence spectrophotometry. Effect of sugars (D-sucrose, D-glucose, and D-fructose) on the epimerization of (+)-catechin and (+)-epicatechin by heating was investigated by HPLC with a β-cyclodextrin stepwise elution mode, in which two kinds of aqueous eluents containing different concentrations of β-cyclodextrin were used by turns. The epimerization of the two enantiomers was suppressed only when D-fructose was added. Separation of ten kinds of catechins including catechin and epicatechin enantiomers was investigated by a β-cyclodextrin linear gradient HPLC elution mode without using organic solvents, where two kinds of aqueous eluents containing different concentrations of β-cyclodextrin were used with changing their ratio gradually. These catechins in a green tea infusion could be separated successfully by this method.
查看更多>>摘要：? 2022Development of green approaches have emerged as a challenge that highlight the pressing need for nontoxic solvents, miniaturized method and bio-degradable materials. In this regard, an environmentally-friendly microfluidic system based on natural deep eutectic solvents (DESs) immobilized in agarose membranes was developed to extract parabens from urine samples for the first time. A comprehensive study of the support liquid membrane showed that only 3 μL of camphor and thymol (2:1 molar ratio) was an interesting option as a substitute for conventional (toxic) solvents used to date. Other experimental conditions were optimized and pH 4 (HCl) and 12 (NaOH) were selected as sample and acceptor solution, respectively. Both solutions (sample and acceptor) were fixed at 1 μL min?1 as flow rate. The proposed green microfluidic device was successfully applied for the determination of parabens in urine samples with relative recoveries between 86 and 100% for all analytes. Detection limits and quantitation limits were between 0.011–0.093 and 0.31–0.38 μg mL?1, respectively. Relative standard deviation was below 7% for all analytes. Furthermore, the environmentally-friendly solvent (Ca:Ty 2:1) used as SLM offered the same advantages in terms of membrane stability allowing consecutive extractions. Results were compared with experiments previously conducted using conventional (polypropylene) membranes, observing that highly green microextraction systems based on natural and biodegradable materials have proven to be an attractive alternative in microfluidic systems.
查看更多>>摘要：? 2022 Elsevier B.V.The alteration of lipid profile in biological specimens, such as plasma, mirrors abnormalities in their homeostasis and offers pivotal information for disease comprehension. Fast analytical methods are needed to highlight changes in plasma lipid profile and deliver rapid results. In this study we developed a fast reversed phase ultra high performance liquid chromatography-trapped ion mobility mass spectrometry (RP-UHPLC-TIMS-MS) method for untargeted lipidomics. A short, narrow-bore fully porous particle CSH column (50 mm × 2.1 mm, 1.7 μm) was used, and by selecting appropriate flow rate, temperature and gradient conditions, the total analysis time was reduced from 20 to 4 min. TIMS was operated in parallel accumulation serial fragmentation mode (PASEF) which allowed to select multiple precursors for MS/MS and separate co-eluting lipids based on their different mobility. Lipid annotation was performed by rule-based approach, comparison with LipidBlast spectral library and manual data curation, by taking into account class-specific fragmentation pattern, accurate mass, adduct form, retention behavior in RP and comparison of their collision cross-section (CCS) values for increased confidence. 306 unique lipids from 21 subclasses were annotated from 20 μL of plasma, while their concentration was estimated by class-specific deuterated internal standards. The analytical method was validated and finally applied to elucidate the alteration of plasma lipid profiles in a small cohort of amyotrophic lateral sclerosis (ALS) patients. Univariate and multivariate statistics evidenced significant differences with respect to control patients, particularly in the levels of ether linked lipids (PC-O, PE-O, PE-P and LPC-O), sphingolipids (Ceramides), and triacylglycerols, showing the usefulness of this fast approach in providing accurate and rapid results with respect to longer (≥15 min) untargeted UHPLC-HRMS methods.
查看更多>>摘要：? 2022 The Author(s)Many pharmacologically active compounds are chiral species, and their therapeutic or toxicological effects might differ between isomers. Herein, we develop a fast and sensitive chiral analysis methodology for the determination of eight pharmaceuticals, considered as emerging environmental pollutants and belonging to two different chemical classes, in wastewater and sludge samples. Compounds were separated using supercritical fluid chromatography (SFC) combined with time-of-flight mass spectrometry (TOF-MS) detection. The stationary phase, the modifier and the additive combined with supercritical carbon dioxide (CO2), in the SFC mobile phase, played a major effect in the enantiomeric resolution of selected compounds. Moreover, the composition of the mobile phase affected their ionization efficiency in the electrospray ionization source. Methanol (MeOH), containing a 0.1% of ammonia, was used as CO2 modifier for the separation of compounds in a polysaccharide-type column. Total analysis time was 15.5 min, achieving resolution factors between 1.03 and 2.49 for the eight pairs of enantiomers. In combination with mixed-mode solid-phase extraction and matrix solid-phase dispersion protocols, compounds were determined in wastewater and sludge samples, with limits of quantification in the range of 0.010–0.020 μg L?1 and 3.7–11.1 ng g?1, for aqueous and solid samples, respectively. The amine-type drugs (tramadol, propranolol and venlafaxine) were mostly found in wastewater samples, whilst azolic antimycotics were mainly quantified in sludge. The first group of compounds showed enantiomeric fractions significantly different to those existing in the commercial counterpart pharmaceuticals.
查看更多>>摘要：? 2022Electrochemical deposition has been proposed as a promising approach for in situ immobilization of metal-organic framework (MOF) on conductive surfaces. It is favorable as it is time-saving, green, and does not require vigorous reaction conditions, which can be applied to the synthesis and immobilization of extraction materials for fiber in-tube solid phase microextraction. In this work, PPF-1 was immobilized on the surface of the carbon fibers by electrochemical method. The novel method overcame the problems including strict conditions and time-consuming operation. The modified carbon fibers were packed into the PEEK tube for extraction and analysis of three non-steroidal anti-inflammatory drugs (NSAIDs), which performed good extraction efficiency due to strong hydrogen bonding, hydrophobic interaction and π-π interaction between PPF-1 and analytes. The established method obtained good enrichment performance (enrichment factor between 230-540), low limits of detection (between 0.01-0.03 ng/mL), good linearity and good reproducibility (RSDs≤4.93%), which was successfully applied for the quantitative analysis of NSAIDs in human plasma samples.
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