Xiupei Yang,Xiumei Cheng,Yingyun Lin,Zhijing Tan,Linxiang Xie,Martin M.F. Choi
This study reports a sweeping and micelle to solvent stacking (MSS) method for fast stacking of nitroimidazoles in capillary zone electrophoresis (CZE). The optimal experimental conditions are run buffer of 25 mM sodium phosphate (pH 1.5) and 0.50% (v/v) methanol, micellar solution of 30 mM sodium dodecyl sulfate, applied voltage of 28 kV, and sample and micellar solution injection of 100 s. By applying this new on-line preconcentration technique, the nitroimidazoles content can be determined within 9 min with the limit of detection ( S / N = 3) ranging 2.3–3.0 ng/mL, which is lower than that of conventional CZE analysis. The proposed MSS technique affords 20-, 12- and 38-fold improvements in sensitivity for the detection of dimetridazole, metronidazole and secnidazole, respectively. The relative standard deviations (RSDs) of intra-day and inter-day are 2.1–3.6% and 2.7–4.6% ( n = 6), respectively. The recoveries in pretreated rabbit plasma at spiked levels of 5.0–10.0 μg/mL are 92.0–101.1% with RSDs lower than 3.4%. The proposed sweeping and MSS-CZE is a highly sensitive method for the detection of nitroimidazoles in biological and clinical samples and has been successfully applied to analyze nitroimidazoles in pretreated rabbit plasma.
In this paper, iminodiacetic acid-Cu(II) functionalized Fe 3 O 4 @SiO 2 magnetic nanoparticles were prepared and used as new adsorbents for magnetic solid phase extraction (MSPE) of six monoamine neurotransmitters (MNTs) from rabbit plasma. The selective enrichment of MNTs at pH 5.0 was motivated by the specific coordination interaction between amino groups of MNTs and the immobilized Cu(II). The employed weak acidic extraction condition avoided the oxidation of MNTs, and thus facilitated operation and ensured higher recoveries. Under optimal conditions, the recoveries of six MNTs from rabbit plasma were in the range of 83.9–109.4%, with RSD of 2.0–10.0%. When coupled the Cu(II) immobilized MSPE with high-performance liquid chromatography-fluorescence detection, the method exhibited relatively lower detection limits than the previously reported methods, and the method was successfully used to determine the endogenous MNTs in rabbit plasma. The proposed method has potential application for the determination of MNTs in biological samples. Also, the utilization of coordination interaction to improve the selectivity might open another way to selectively enrich small alkaloids from complex samples.
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