Abd El-Hady Deia, Albishri Hassan M, Rengarajan Rajesh, Wätzig Hermann
Chemistry Department, Faculty of Science, King Abdulaziz University, North Jeddah, Saudi Arabia; Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt.
Electrophoresis. 2014 Jul;35(14):1956-64. doi: 10.1002/elps.201400073. Epub 2014 Jun 11.
Methotrexate (MTX) is widely used for the treatment of many types of cancer. Folinic acid (FNA) and folic acid (FA) were usually simultaneously supplemented with MTX to reduce the side effects of a folate deficiency. This study, for the first time, included on-line sample preconcentration by stacking and sweeping techniques under reduced or enhanced electric conductivity in the sample region using short chain alkyl imidazolium ionic liquids (ILs) as micelle forming agents for analyte focusing. Both analyte focusing by micelle collapse (AFMC) and sweeping-MEKC had been investigated for the comparison of their effectiveness to examine simultaneously MTX, FNA and FA in plasma and urine under physiological conditions. In sweeping-MEKC, the sample solution without micelles was hydrodynamically injected as a long plug into a fused-silica capillary pre-filled with phosphate buffer containing 3.0 mol/L of 1-butyl-3-methylimidazolium bromide (BMIMBr). Using AFMC, the analytes were prepared in BMIMBr micellar matrix and hydrodynamically injected into the phosphate buffer without IL micelles. The conductivity ratio between BGE and sample (γ, BGE/sample) was optimized to be 3.0 in sweeping-MEKC and 0.33 in AFMC resulting the adequate separation of analytes within 4.0 min. To reduce the possibility of BMIMBr adsorption, an appropriate rinsing protocol was used. The limits of detection were calculated as 0.1 ng/mL MTX, 0.05 ng/mL FNA and 0.05 ng/mL FA by sweeping-MEKC and 0.5 ng/mL MTX, 0.3 ng/mL FNA and 0.3 ng/mL FA by AFMC. The accuracy was tested by recovery in plasma and urine matrices giving values ranging between 90 and 110%. Both stacking and sweeping by BMIMBr could be successfully used for the rapid, selective and sensitive determination of pharmaceuticals in complex matrices due to its fascinating properties, including high conductivity, good thermal stability and ability to form different types of interactions by electrostatic, hydrophobic, hydrogen bonding and π-π interactions. In sweeping-MEKC, the using of BMIMBr enhanced the γ factor, k retention factor and the injected amount of sample. Consequently, this technique offers particular potential for higher sensitivity by giving 22- and 5-fold sensitivity enhancement factors (SEFs) of MTX compared to CZE and AFMC, respectively.
甲氨蝶呤（MTX）被广泛用于多种癌症的治疗。通常会同时补充亚叶酸（FNA）和叶酸（FA）以减轻叶酸缺乏带来的副作用。本研究首次采用短链烷基咪唑鎓离子液体（ILs）作为胶束形成剂，通过堆积和扫集技术在样品区域降低或增强电导率的情况下进行在线样品预富集，以实现分析物聚焦。研究了胶束塌陷分析物聚焦（AFMC）和扫集-胶束电动毛细管色谱法（sweeping-MEKC），比较它们在生理条件下同时检测血浆和尿液中甲氨蝶呤、亚叶酸和叶酸的有效性。在扫集-胶束电动毛细管色谱法中，将不含胶束的样品溶液以长塞的形式通过流体动力学方式注入预先填充有含3.0 mol/L溴化1-丁基-3-甲基咪唑鎓（BMIMBr）的磷酸盐缓冲液的熔融石英毛细管中。使用AFMC时，分析物在BMIMBr胶束基质中制备，然后通过流体动力学方式注入不含离子液体胶束的磷酸盐缓冲液中。优化了背景电解质（BGE）与样品之间的电导率比（γ，BGE/样品），在扫集-胶束电动毛细管色谱法中为3.0，在AFMC中为0.33，从而在4.0分钟内实现了分析物的充分分离。为了降低BMIMBr吸附的可能性，采用了适当的冲洗方案。通过扫集-胶束电动毛细管色谱法计算出的检测限为甲氨蝶呤0.1 ng/mL、亚叶酸0.05 ng/mL和叶酸0.05 ng/mL，通过AFMC计算出的检测限为甲氨蝶呤0.5 ng/mL、亚叶酸0.3 ng/mL和叶酸0.3 ng/mL。通过在血浆和尿液基质中的回收率测试了准确性，回收率在90%至110%之间。由于BMIMBr具有高电导率、良好的热稳定性以及通过静电、疏水、氢键和π-π相互作用形成不同类型相互作用的能力等迷人特性，其堆积和扫集均可成功用于复杂基质中药物的快速、选择性和灵敏测定。在扫集-胶束电动毛细管色谱法中，BMIMBr的使用提高了γ因子、保留因子（k）和样品进样量。因此，与毛细管区带电泳（CZE）和AFMC相比，该技术分别使甲氨蝶呤的灵敏度提高了22倍和5倍，具有更高灵敏度的特殊潜力。
