Jimidar M, Hamoir T P, Foriers A, Massart D L
Department of Pharmaceutical and Biomedical Analysis, Vrije Universiteit Brussel, Belgium.
J Chromatogr. 1993 Apr 23;636(1):179-86. doi: 10.1016/0021-9673(93)80070-o.
A capillary zone electrophoretic (CZE) method was developed to determine caffeine, aspartame and benzoic acid in diet cola soft drinks and in artificial sweetening powders. The effects of pH, ionic strength, organic solvents and different buffers were investigated to select the optimum conditions. These consisted of a sodium phosphate buffer at pH 11 and ionic strength 0.025. The running voltage was set at 15 kV and the injection was performed hydrostatically for 30 s. The CZE method was then compared with a previously developed high-performance liquid chromatographic (HPLC) method in terms of repeatability, reproducibility, accuracy, linearity, sensitivity and separation efficiency. Both methods gave good repeatability. The relative standard deviations for reproducibility were significantly higher in CZE than in HPLC. The main reason for this is probably the condition of the wall of the capillary, which was difficult to keep constant between the days of analysis. The separation efficiency of CZE was 65-110 times higher than that of HPLC; on the other hand, 10-20 times lower detection limits were obtained in HPLC. Both methods were linear, but the linear ranges were different owing to the lower detection limit of HPLC. In CZE, the effect of the matrix was higher.
开发了一种毛细管区带电泳（CZE）方法，用于测定健怡可乐软饮料和人工甜味剂粉末中的咖啡因、阿斯巴甜和苯甲酸。研究了pH值、离子强度、有机溶剂和不同缓冲液的影响，以选择最佳条件。这些条件包括pH值为11、离子强度为0.025的磷酸钠缓冲液。运行电压设定为15 kV，采用静水压进样30 s。然后将CZE方法与先前开发的高效液相色谱（HPLC）方法在重复性、再现性、准确性、线性、灵敏度和分离效率方面进行比较。两种方法都具有良好的重复性。CZE方法中再现性的相对标准偏差明显高于HPLC方法。主要原因可能是毛细管内壁的状况，在分析的不同日期之间难以保持恒定。CZE方法的分离效率比HPLC方法高65 - 110倍；另一方面，HPLC方法的检测限低10 - 20倍。两种方法都呈线性，但由于HPLC方法的检测限较低，线性范围不同。在CZE方法中，基质的影响更大。
