Quirino Joselito P
Australian Centre for Research on Separation Science/School of Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia.
J Chromatogr A. 2008 Dec 19;1214(1-2):171-7. doi: 10.1016/j.chroma.2008.10.074. Epub 2008 Nov 1.
The operating parameters that affect the performance of analyte focusing by micelle collapse (AFMC) to neutral analytes (i.e., dialkyl phthalates) in normal migration micellar electrokinetic chromatography (NM-MEKC) are examined. NM-MEKC is characterized by an electroosmotic flow greater than the electrophoretic velocity of the micellar pseudostationary phase, and was performed using sodium dodecyl sulfate (SDS) with neutral to high pH electrolytes in fused silica capillaries. AFMC is a recently introduced on-line sample preconcentration technique in capillary electrophoresis that can provide hundreds fold improvement in detection sensitivity. The mechanism of AFMC is based on the analyte transport, release, and accumulation by the moving surfactant micelles [e.g., SDS at concentrations closer to the critical micelle concentration (CMC)] in the sample that dilutes below its CMC into a liquid phase zone. The sample is prepared in a matrix that contains SDS micelles and high mobility anions, where the conductivity of the sample matrix is higher compared to that of the separation solution. The sample injection length, sample and separation solution conductivity ratio, and surfactant micelle concentration in the sample were found to affect the AFMC performance, as well as the effective separation length in NM-MEKC. The use of a different electrolyte salt in the sample and separation solution also affected AFMC NM-MEKC results. In particular, sodium chloride in the sample matrix can induce a micelle-mediated neutral analyte isotachophoretic concentration that is detrimental to the technique.
研究了在正常迁移胶束电动色谱（NM-MEKC）中，影响通过胶束塌陷实现分析物聚焦（AFMC）对中性分析物（即邻苯二甲酸二烷基酯）性能的操作参数。NM-MEKC的特征是电渗流大于胶束假固定相的电泳速度，使用十二烷基硫酸钠（SDS）与中性至高pH值电解质在熔融石英毛细管中进行。AFMC是最近在毛细管电泳中引入的一种在线样品预浓缩技术，可使检测灵敏度提高数百倍。AFMC的机制基于分析物在样品中被移动的表面活性剂胶束（例如，浓度接近临界胶束浓度（CMC）的SDS）传输、释放和积累，样品在低于其CMC的情况下稀释到液相区。样品在含有SDS胶束和高迁移率阴离子的基质中制备，其中样品基质的电导率高于分离溶液的电导率。发现样品进样长度、样品与分离溶液的电导率比以及样品中表面活性剂胶束浓度会影响AFMC性能，以及NM-MEKC中的有效分离长度。在样品和分离溶液中使用不同的电解质盐也会影响AFMC NM-MEKC的结果。特别是，样品基质中的氯化钠会诱导胶束介导的中性分析物等速电泳浓缩，这对该技术不利。
