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A novel and sensitive high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of valproic acid (VPA) in human plasma. The method was based on derivatization of VPA using 2-bromo-2′-acetonaphthone as a new derivatization reagent. Caprylic acid was used as an internal standard (IS). Under the optimized extraction and derivatization conditions, the method showed good linearity in the range of 0.05–200 μg mL−1 and the limit of detection was as low as 0.01 μg mL−1. The relative standard deviation for intra-day and inter-day (n = 5) was <5%. The recovery ranged from 95.2 to 101.4%. The proposed method is proved to be highly sensitive, simple and rapid, and was successfully applied to the analysis of VPA in plasma samples from patients with generalized epilepsy. [ABSTRACT FROM PUBLISHER]

A simple sample preparation method has been developed for the determination of amoxicillin in human plasma by hollow fiber centrifugal ultrafiltration (HF–CF–UF). A 400-μL plasma sample was placed directly into the HF–CF–UF device, which consisited of a slim glass tube and a U-shaped hollow fiber. After centrifugation at 1.25 × 103 g for 10 min, the filtrate was withdrawn from the hollow fiber and 20 µL was directly injected into the high-performance liquid chromatography (HPLC) for analysis. The calibration curve was linear over the range of 0.1–20 µg/mL (r = 0.9996) and the limit of detection was as low as 0.025 µg/mL. The average recovery and absolute recovery were 99.9% and 84.5%, respectively. Both the intra-day and inter-day precisions (relative standard deviation) were less than 3.1% for three concentrations (0.25, 2.5 and 10 µg/mL). The sample preparation process was simplified. Only after a single centrifugal ultrafiltration can the filtrate be injected directly into HPLC. The present method is simple, sensitive and accurate. It could be effective for the analysis of biological samples with high protein contents, especially for the biopharmaceutical analysis of drugs that use traditional isolation techniques for sample preparation such as the protein precipitation method. [ABSTRACT FROM AUTHOR]

This study used the general applicability of 2,6-didi-o-methyl-β-cyclodextrin (DM-β-CD) as the chiral selector in capillary electrophoresis for fast and efficient chiral separation of repaglinide enantiomers. A systematic study of the parameters affecting separation was performed with UV detection at 243 nm. The optimum conditions were determined to be 1.25% (w/v) DM-β-CD in 20 mM sodium phosphate (pH 2.5) as the running buffer and separation voltage at 20 kV. DM-β-CD had the best enantiomer resolution properties under the tested conditions, whereas other β-cyclodextrins showed inferior performances or no performance. The proposed method had a linear calibration curve in the concentration range of 12.5–400 µg/mL. The limit of detection was 100 ng/mL. The intra-day and inter-day precisions were 2.8 and 3.2%, respectively. Recoveries of 97.9–100.9% were obtained. The proposed method was fast and convenient, and was determined to be efficient for separating enantiomers and applicable for analyzing repaglinide enantiomers in quality control of pharmaceutical production. [ABSTRACT FROM PUBLISHER]

A simple, accurate and sensitive ionic liquid-based headspace single-drop microextraction procedure followed by high-performance liquid chromatography was developed and validated for the determination of camphor and trans-anethole in compound liquorice tablets. The volume of the ionic liquid microdrop was increased to 12 µL by modifying the device of the suspended drop. The stability of the microdrop and the sensitivity of the method were improved. Under the optimum experimental conditions, the calculated calibration curves gave acceptable linearity for camphor and trans-anethole with correlation coefficients of 0.9990 and 0.9998, respectively. The repeatability of the proposed method, expressed as relative standard deviation, was below 4.5% (n = 5). The limits of detection for the two target analytes were found to be 9.77 and 1.95 × 10−2 μg/mL, respectively. In this study, the separation, purification and enrichment were achieved in one step in an airtight system, which reduced the interferences caused by other complicated constituents, increased the signal-to-noise of the method and ensured the accuracy of the results because there was no loss of volatile components. It is expected to be widely applied for sample pretreatment of volatile components with high boiling points in samples with complicated matrices such as the extractions of plants or Chinese traditional drugs. [ABSTRACT FROM PUBLISHER]

This paper presents a novel and simple cleanup procedure based on hollow fiber liquid-phase microextraction (HF-LPME) for the determination of trace estradiol in environmental. Estradiol was extracted from a 140-mL water sample (the donor phase) into the pores of the hollow fiber wall organic solvent, then into the organic solvent (the acceptor phase) in the lumen of the hollow fiber. Afterwards, the hollow fiber was eluted with methanol to capture estradiol from the acceptor phase. Different experimental parameters, including the organic phase type and its volume, compositions of the donor phases, ionic strength, stirring rate, temperature, and the extraction times were controlled and optimized based on the response of the HPLC instrument. Under the optimized experimental conditions, the proposed method was found to be linear in the concentration of 1-1000 ng/mL for estradiol, and the limit of detection was 0.1 ng/mL. Furthermore, the method provided a good enrichment factor of 300, and repeatability (relative standard deviation = 5.5). Finally, the proposed method was applied for the analysis of real environmental samples.