COMPARISON OF CAPILLARY ZONE ELECTROPHORESIS WITH HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY FOR THE DETERMINATION OF ADDITIVES IN FOODSTUFFS

A capillary zone electrophoretic (CZE) method was developed to determi ne caffeine, aspartame and benzoic acid in diet cola soft drinks and i n artificial sweetening powders. The effects of pH, ionic strength, or ganic solvents and different buffers were investigated to select the o ptimum 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 w as then compared with a previously developed high-performance liquid c hromatographic (HPLC) method in terms of repeatability, reproducibilit y, accuracy, linearity, sensitivity and separation efficiency. Both me thods gave good repeatability. The relative standard deviations for re producibility 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. T he separation efficiency of CZE was 65-1 10 times higher than that of HPLC; on the other hand, 10-20 times lower detection limits were obtai ned in HPLC. Both methods were linear, but the linear ranges were diff erent owing to the lower detection limit of HPLC. In CZE, the effect o f the matrix was higher.