Journal of separation science最新文献

Matrix effects in gas chromatography (GC) are typically regarded as an analytical drawback, as co-eluting compounds can distort analyte quantification. This study demonstrates that a transient matrix effect can be deliberately induced to enhance GC–MS sensitivity for environmental pollutants. Four classes of high-boiling protectants—alcohols, amines, carboxylic acids, and polyethylene glycols (PEGs)—were systematically evaluated for their ability to increase detector response for polycyclic aromatic hydrocarbons (PAHs), chlorophenols, and nitrophenols. The influence of protectant type, sample solvent, injector temperature, and initial column temperature on signal enhancement was investigated. Among all protectants, PEGs yielded the highest improvements, with average signal increases of 280% for PAHs and 380% for chlorophenols and nitrophenols. The transient nature of the effect was confirmed through alternating injections, ensuring no cumulative influence on subsequent analyses. Application of the QuEChERS method to water and soil samples showed comparable enhancements, with minimal interference from matrix components. Method validation for PEG-400 confirmed excellent linearity (R² > 0.998), two- to threefold lower LODs, and high precision (RSD < 4.3%), demonstrating robustness and reproducibility. Leveraging a controlled transient matrix effect, this approach achieves several-fold improvement in detection limits without altering chromatographic hardware, providing a simple and adaptable tool for trace-level environmental monitoring.

Portable instruments allow for on-site real-time analyses and generally take up less resources compared to standard-sized instruments. In this project, we tested the suitability of a portable liquid chromatograph for seized drug screening and how it, alone, may fulfill the requirements set forth by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG). For this study, we used a portable liquid chromatograph, which employed a dual column system with on-column dual UV-LED detection. All 16 drugs representing different drug classes could be identified by a combination of dual relative retention times and dual UV absorbance ratios. Most classical drugs, which represent non-novel psychoactive compounds, could be identified based on the SWGDRUG guidelines. These results suggest the potential for liquid chromatography to be performed in the field using portable devices and to provide a greener alternative to traditional liquid chromatography due to greatly reduced solvent consumption.

Routine monitoring of vancomycin drug concentrations is crucial for optimizing dosages to ensure therapeutic efficacy and minimize adverse effects. Vancomycin's clearance is highly correlated with creatinine clearance. However, in developing countries, the majority of hospitals lack the on-site capacity to measure vancomycin concentrations. Dried plasma spots have emerged as an innovative alternative for biological sample collection. Dried plasma spots facilitate the convenient and rapid acquisition of plasma samples, which are highly suitable for both storage and transportation, and can be dispatched to vancomycin testing laboratories. This study presents a validated methodology for the simultaneous quantification of vancomycin and creatinine in dried plasma spots through liquid chromatography-tandem mass spectrometry. Vancomycin demonstrated excellent linearity within the range 3–50 µg/mL, while creatinine exhibited linearity from 1 to 70 µg/mL (both with r² > 0.995). The trueness of all compounds was maintained within ± 15%, the precision was less than 15%, and the recoveries were within acceptable boundaries. Moreover, no significant matrix effects were detected. By employing the Passing–Bablok and Bland–Altman methods, we compared the differences and consistencies between the wet plasma concentrations and dried plasma spot concentrations of vancomycin and creatinine in 71 samples. The results revealed no significant distinctions between the two approaches and showcased comparable consistencies, implying that the dried plasma spots technique can be effectively utilized for the simultaneous determination of vancomycin and creatinine in plasma.

This work aims to develop a capillary based on molecularly imprinted polymer coating for the on-line preconcentration and selective determination of lysozyme in egg white, combining the template immobilization strategy, surface imprinting approach, and post-imprinting modification strategy by using capillary electrophoresis. First, the capillary was coated with polydopamine and then the 3-mercaptopropionic acid coating was formed through self-assembly for subsequent immobilization of template lysozyme. Afterward, the surface-imprinted polydopamine coating was fabricated by the self-polymerization of dopamine as a functional monomer and cross-linker. After that, partially hydrolyzed poly(2-methyl-2-oxazoline), which possesses the protein-resistant adsorption ability, was introduced to reduce the nonspecific adsorption of the polydopamine coating. Finally, lysozyme molecularly imprinted polymer coated capillaries were obtained after lysozyme was eluted. The created coating was characterized by electroosmotic flow mobility measurements, scanning electron microscope, static water contact angle, and attenuated total reflection Fourier-transform infrared spectrum. Lysozyme standard solutions (concentration from 0.5 to 10.0 ng/mL) were analyzed using the fabricated capillary, achieving the detection limit of 0.1 ng/mL. In addition, the accuracy, repeatability, reproducibility, and selectivity of the prepared capillary were investigated. The recovery values of lysozyme gained were from 96.0% to 98.7% for hen egg white samples using the developed capillary.

Traditional approaches, such as gas chromatography-mass spectrometry (GC-MS), are complemented by adopting new liquid chromatographic methods to separate isomeric drug mixtures that are unresolvable by the former technique. This study investigates a series of liquid chromatographic approaches using both traditional and silica hydride stationary phases. These methods focus on the separation of 11 synthetic cannabinoid constitutional isomers. Seven different columns were used to assess the utility of single and serially coupled column approaches under reversed-phase conditions. The best separation using a single column was the use of a Cogent Pentafluorophenyl (RP PFP) stationary phase, where 9 out of 11 constitutional isomers were separated. Concerning using different single columns with the same organic modifier or different organic modifiers with the same column, all compounds of interest were separated using a combination of RP PFP and RP C18 columns using methanol as the organic modifier. Cogent RP C18 separated all constitutional isomers (R_s = 1) in two separate runs, using methanol and acetonitrile individually. The serial coupling of columns, which did not offer better separation compared to the previous techniques, demonstrated either enhanced or diminished selectivity based on column coupling.

Comparing predicted and measured retention times can greatly enhance the reliability of peptide identification in LC-MS analysis of smaller, food-derived peptides where MS spectral information alone is often insufficient. Unfortunately, the extensive data sets of peptide retention times from proteomics repositories, or prediction models derived from them, have limited applicability to food-derived peptides due to the structural diversity of these peptides. To address this, we applied a transfer learning approach by fine-tuning a generic deep learning model initially trained on large proteomics datasets using our own experimental data obtained from commercial peptide standards.

The method utilizes an easy to implement retraining strategy that significantly reduces data requirements and training time compared to building a model from scratch. The retrained model demonstrated strong predictive performance (Q² > 0.98), and 95% of the retention time predictions of a yeast protein hydrolysate validation set fell within a ±1.0 min window across a wide range of chromatographic conditions, demonstrating both its robustness and practical relevance. We further validated this approach by applying it to the analysis of plant protein hydrolysates. The good performance seen showed its versatility and applicability for diverse sets of peptides including tryptic and non-tryptic peptides.

Our work underscores the potential of transfer learning in chromatographic analysis, providing an efficient and adaptable tool for rapid and reliable peptide analysis in food research. Transfer learning enabled the utilization of extensive databases from the proteomics area in the much narrower and specialized field of food peptide analysis.

Baihe Dihuang decoction (BDD), composed of Lilii Bulbus and Rehmanniae Radix, is a classical Chinese herbal formula. It demonstrates clinical applications in treating emotional disorders and anxiety. In this study, we characterized the chemical basis of BDD in vitro and elucidated its metabolic pathways, pharmacokinetic profiles, and tissue distribution in vivo. An ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) was used to qualitatively characterize the chemical constituents and their metabolites in rat plasma after oral administration of BDD. Then a reliable, sensitive, and accurate quantitative method based on an ultra-high performance liquid chromatography triple quadrupole mass spectrometry (UHPLC-QqQ-MS) was employed to investigate the pharmacokinetics of nine major compounds and the tissue distribution of six of these compounds in rats. Results showed that 97 constituents including iridoid glycosides, phenylethanoid glycosides, phenolic acid glycerides, alkaloids, and other types of components were identified in BDD. A total of 28 prototype constituents and 66 metabolites were identified in rat plasma samples. The related metabolic pathways mainly involved deglycosylation, methylation, and deoxygenation. The pharmacokinetic results showed that the analytes displayed rapid absorption and elimination. Tissue distribution analysis revealed that all analytes were detected in heart, liver, spleen, lung, and kidney at 0.5 h after administration and presented higher concentrations in the lung and kidney compared to other tissues. This study provides a reference for clinical application and new drug development of BDD.

1-Methyl-9-(3-pyridinylmethyl)-9H-pyrido[3,4-b] indole (HMYB) is a novel semi-synthetic alkaloid derived from β-carboline harmane, which has been proven to be effective in treatment of encopresis. But the pharmacokinetic characteristics of HMYB were not yet illustrated. In this study, three metabolites (harmane, harmol, and 7-OH-HMYB) of HMYB were isolated from rat urine after oral administration of HMYB and authenticated with nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. Most significantly, HMYB and its three metabolites were simultaneously quantified accurately in rat plasma using a quick, sensitive and selective UHPLC-MS/MS method. On an ACQUITY UPLC BEH C18 column (2.1 × 50 mm, 1.7 µm), the analytes and internal standard (osalmid) were separated by gradient elution using acetonitrile and water containing 0.1% formic acid at a flow rate of 0.4 mL/min. The mass spectrometry detector was used in positive ionization mode for multiple reaction monitoring. The method showed good linearity over the concentration range of 0.5–500 ng/mL for HMYB and three metabolites. The method was applied to the pharmacokinetic study of HMYB and its three metabolites after oral doses of HMYB (25, 50, and 100 mg/kg) and intravenous administration of 0.5 mg/kg in rats. Pharmacokinetic differences between HMYB and its three metabolites were determined, along with the absolute bioavailability of HMYB. These results would be helpful in understanding the efficacy of HMYB. The results will also contribute to providing guidance for the structural modification of more effective semi-synthetic derivatives.

Metabolite quantification without a radiolabeled analogue or the reference standard is challenging. This study presented a novel high resolution mass spectrometry (HRMS)-based analytical strategy for simultaneous metabolite profiling and standard-free metabolite quantification of drug candidates with limited restriction on structure. The model drug was artemisinin (ART), which is widely used in clinic to treat malaria. A major hydroxylated metabolite (M1) with minor isomer M2 was first found for ART in human liver microsomes using LC-HRMS. Second, the MS response ratio (MRR) of the hydroxylation pathway in specific biological matrix was investigated using several probe substituents (midazolam, etc.). In contrast to varying (0.5–1.9-fold difference) MS response of probe drugs and their metabolites at equimolar concentration, the MRR ratio of the hydroxylation pathway was relatively constant (∼0.6-fold). Third, simulated calculation curves for M1 were obtained based on the calibration curves of ART and the MRR ratios of the hydroxylation pathway. Fourth, the present analytical strategy provided reliable (< 31.7% deviation from that obtained using a validated LC-MS technique) quantitative data on enzyme kinetics and pharmacokinetics. As a result, M1 was found to be the predominant metabolite for ART (3.6-fold of ART exposure) in human, and another unidentified hydroxylated metabolite M2 accounted for ∼40.0% of ART exposure. The results demonstrated that the new HRMS-based analytical strategy along with the MRR ratio of a metabolic pathway evaluated by appropriate probe substituents can be a valuable tool for the simultaneous metabolite profiling and standard-free metabolite quantification in early drug development.