Santagati Natale Alfredo, Tropea Salvatore, Ronsisvalle Giuseppe
Dipartimento di Scienze Farmaceutiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy.
J Chromatogr A. 2005 Jul 15;1081(1):77-86. doi: 10.1016/j.chroma.2005.05.004.
In order to enhance the UV detection sensitivity, an application study of an on-line preconcentration technique for micellar electrokinetic chromatographic (MEKC) was carried out. The simultaneous determination of four test ecdysteroids, 20-hydroxyecdysone, ajugasterone C, polypodine B and ponasterone A has been investigated by using the normal stacking mode in MEKC with UV detection. The effects of anionic surfactant composition and concentration, the applied voltage, the pH buffer, the kind and the amount of organic solvent and the injection time on the analyte resolution were evaluated. The optimised conditions for the separation involved the use of a 50 mM borate as the running buffer containing 50 mM of a mixture of sodium dodecyl sulphate (SDS) and sodium cholate (SC) in the ratio of 1:1 together with a concentration of 10% (v/v) of 2-PrOH at pH 9.0. Hydrodynamic injection of 12 s at 50 mbar and separation voltage of 20 kV at temperature of 20 degrees C were employed. These conditions allowed a repeatability separation within 21 min. Concentration detection limit for the neutral analytes studied improve about an order of magnitude. The method was also applied to the determination of ecdysteroids in a real sample.
为提高紫外检测灵敏度，开展了胶束电动色谱（MEKC）在线预富集技术的应用研究。采用MEKC中的正常堆积模式结合紫外检测，对4种受试蜕皮甾体（20-羟基蜕皮酮、筋骨草甾酮C、多足甾酮B和蜕皮甾酮A）进行了同时测定。评估了阴离子表面活性剂组成和浓度、施加电压、pH缓冲液、有机溶剂种类和用量以及进样时间对分析物分离度的影响。优化的分离条件包括使用50 mM硼酸盐作为运行缓冲液，其中含有50 mM十二烷基硫酸钠（SDS）和胆酸钠（SC）按1:1比例混合的混合物，以及在pH 9.0时10%（v/v）的2-丙醇。在50 mbar下进行12 s的流体动力学进样，在20℃温度下分离电压为20 kV。这些条件可在21分钟内实现重复性分离。所研究的中性分析物的浓度检测限提高了约一个数量级。该方法还应用于实际样品中蜕皮甾体的测定。
