柱前衍生-酸诱导瞬时等速堆积柱上富集毛细管电泳法测定巯基化合物

Determination of Mercapto Compounds by Pre-column Derivatization-Acid-induced Transient Isotachophoretic Stacking Capillary Electrophoresis

建立了柱前衍生-酸诱导瞬时等速堆积柱上富集毛细管电泳测定巯基化合物的方法。在Tris-HCl缓冲溶液(p H=8.15)中,巯基化合物与2-氯-1-甲基碘化吡啶在室温条件下反应10 min;随后,将反应混合物引入到充满40 mmol/L甲酸盐背景电解质溶液(pH=3.96)的毛细管柱内;最后,向毛细管柱中引入适量稀H_2SO_4溶液。当在毛细管柱两端施加正向电压时,衍生的巯基化合物就会经瞬时等速堆积电泳过程而发生富集,其中前导和尾随离子分别为H^+和Tris^+。以半胱氨酸和巯基乙酸为分析对象,检测波长设为312 nm,优化了酸诱导瞬时等速堆积柱上富集的各种实验条件。在最佳条件下,半胱氨酸和巯基乙酸的线性范围分别为10~100 mg/L和4~100 mg/L,检出限分别为0.2和0.4 mg/L。本方法用于脱毛膏中巯基乙酸的测定,结果令人满意。

A new method was developed for the determination of mercapto compounds derivatization combined with acid-induced transient isotachophoretic stacking capillary by pre-column electrophoresis. Mercapto compounds were derivatized with 2-chloro-l-methylpyridinium iodide （CMPI） in Tris-HC1 buffer solution at pH 8. 15 at room temperature. The derivatized mercapto compounds were introduced into the capillary filled up with 40 mmol/L formate buffer （ pH = 3.96）, followed by injection of diluted sulfuric acid. Upon application of voltage at normal polarity, the derivatized mercapto compounds were preconcentrated due to transient isotachophoresis stacking electrophoresis with H^＋ as the leading ion and Tris^＋ as the terminating ion. The detection wavelength was set at 312 nm. Cysteine and sodium thioglycolate were chosen as the models of mercapto compounds to be detected. Various experimental factors influencing transient isotachophoresis stacking were investigated. Under the optimal conditions, the linear relation between peak area and concentration was obtained in the range from 10 mg/L to 100 mg/L for cysteine, and from 4 mg/L to 100 mg/L for sodium thioglycolate. The LODs were 0. 2 mg/L and 0.4 mg/L for cysteine and sodium thioglycolate, respectively. The developed method was successfully applied to the determination of thioglycolate in depilatory cream samples.