咖啡因及其9种类似物的胶束电动毛细管分析研究

 以十二烷基硫酸钠 (SDS)胶束为准固定相 ,考察了咖啡因及其 9种类似物在胶束电动毛细管 (MECC)分离模式下的分离行为。研究了运行缓冲液的 pH值、磷酸盐浓度、SDS浓度、甲醇体积分数、分离电压、分离温度等因素对这 10种化合物的迁移时间和分离效果的影响。结果发现 ,这些因素对上述 10种化合物的分离有显著的影响 ,尤以pH值为最。它不仅影响化合物的迁移时间和分离效率 ,还改变其出峰顺序 ,这与碱性条件下化合物仲胺基上氢的电离有关。优化后的分离条件 :运行缓冲液为 2 0mmol/L磷酸盐 2 0mmol/LSDS(pH 11 0 ) ,分离电压为2 5kV。

Research on the Separation of Caffeine and Its Nine Analoguesby Micellar Electrokinetic Capillary Chromatography

The separation of caffeine and its nine analogues by micellar electrokinetic capillary chromatography (MECC) using sodium dodecyl sulphate (SDS) as the micellar phase was investigated. The effects of pH and concentration of phosphate buffer solution, SDS micelle concentration, methanol volume fraction, applied voltage and temperature on the separation were studied. It was found that the migration of these compounds was affected by these factors, especially by pH of the solution. The order of elution, as well as the migration time and separation efficiency of these compounds changes with the acidity of the solution, which suggests the disassociation of the hydrogen on the secondary amino group in these compounds. The optimized separation conditions consisted of a running buffer of 20 mmol/L sodium phosphate buffer, at pH 11.0, containing 20 mmol/L SDS, with an applied voltage of 25 kV and a temperature of 25 degrees C. All of the compounds were resolved within 9 min with the detection limits of 0.70 mg/L and the linearity in the range of 1.40 mg/L-45.5 mg/L with the correlation coefficients of 0.998-0.999.