Tuberculosis (TB), an infectious disease caused by Mycobacterium tuberculosis, infects approximately one third of the current world population. Isoniazid is one of the most frequently used first-line anti-TB drugs. In this study, we developed a sensitive cation-selective exhaustive injection-sweeping-micellar electrokinetic chromatography method (CSEI-Sweep-MEKC) for analyzing isoniazid in human plasma. Parameters including acetonitrile (ACN) percentage in the separation buffer; the injection time, and concentration of the high-conductivity buffer; sodium dodecyl sulfate (SDS) concentration; phosphate concentration in the sample matrix; and the sample injection time were all optimized to obtain the best analytical performance. The optimal background electrolyte comprised 50 mM phosphate buffer, 100 mM SDS, and 15% ACN. Non-micelle background electrolyte, containing 75 mM phosphate buffer and 15% ACN, was first injected into the capillary, followed by a short plug of 200 mM phosphate (high-conductivity buffer). Run-to-run repeatability (n=3) and intermediate precision (n=3) of peak area ratios were found to be lower than 8.7% and 11.4% RSD, respectively. The accuracy of the method was within 98.1-106.9%. The limit of detection of isoniazod in human plasma was 9 ng mL(-1). Compared with conventional MEKC, the enhancement factor of the CSEI-Sweep-MEKC method was 85 in plasma samples. The developed method was successfully used to determine isoniazid concentration in patient plasma. The results demonstrated that CSEI-Sweep-MEKC has the potential to analyze isoniazid in human plasma for therapeutic drug monitoring and clinical research.

The number of cases of invasive fungal infections (IFIs) has risen significantly in recent years; therefore, this study developed a sensitive and effective sweeping-micellar electrokinetic chromatography (MEKC) method for the simultaneous determination of the three most frequently used triazole antifungal drugs for the treatment of IFIs, which included voriconazole, itraconazole, and posaconazole. Due to the diverse lipophilicity of the tested drugs, the analytical conditions that resulted in good resolution between itraconazole and posaconazole caused the peak for voriconazole to split. The splitting phenomenon was resolved by incorporating a high-salt stacking mechanism into the sweeping-MEKC method. The optimum background electrolyte was composed of 25 mM phosphoric acid solution (pH 2.2), 100 mM sodium dodecyl sulfate, 13 % acetonitrile, and 13 % tetrahydrofuran. The best peak shape of voriconazole was obtained when the conductivity ratio between the sample matrix and background electrolyte was 2.3. Compared to the conventional MEKC mode, the enhancement factor of the sweeping-MEKC method was 66 for itraconazole, 55 for posaconazole, and 43 for voriconazole. The sweeping-MEKC method was validated in terms of precision, accuracy, linearity, specificity, selectivity, and sensitivity. The linearity ranges of the method covered the commonly used therapeutic ranges of the three drugs. The developed sweeping-MEKC method was successfully applied to the analysis of clinical samples, thus demonstrating its applicability for clinical use.

Paliperidone is a new antipsychotic drug with a relatively low therapeutic concentration of 20-60 ng/mL. We established an accurate and sensitive CE method for the determination of paliperidone concentrations in human plasma in this study. To minimize matrix effect caused by quantification errors, paliperidone was extracted from human plasma using Oasis HLB SPE cartridges with three-step washing procedure. To achieve sensitive quantification of paliperidone in human plasma, a high-conductivity sample solution with sweeping-MEKC method was applied for analysis. The separation is performed in a BGE composed of 75 mM phosphoric acid, 100 mM SDS, 12% acetonitrile, and 15% tetrahydrofuran. Sample solution consisted of 10% methanol in 250 mM phosphoric acid and the conductivity ratio between sample matrix and BGE was 2.0 (γ, sample/BGE). The results showed it able to detect paliperidone in plasma samples at concentration as low as 10 ng/mL (S/N = 3) with a linear range between 20 and 200 ng/mL. Compared to the conventional MEKC method, the sensitivity enhancement factor of the developed sweeping-MEKC method was 100. Intra- and interday precision of peak area ratios were less than 6.03%; the method accuracy was between 93.4 and 97.9%. This method was successfully applied to the analysis of plasma samples of patients undergoing paliperidone treatment.