Analysis of ampicillin and its degradation products by capillary electrophoresis

Capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MECC) have been employed for the separation of ampicillin a nd its degradation products, especially the oligomers of ampicillin which a re readily formed during storage and in aqueous solution. Both CZE and MECC are suitable for the separation of the oligomers of ampicillin. MECC is, h owever, more suitable for the separation of other degradation products. Ele ctrophoresis conditions used for the analysis of ampicillin and its degrada tion products were as follows: length of fused (uncoated) silica capillary 44 cm (36 cm effective length), 50 mu m i.d.; voltage, 15 kV; temperature, 25 degrees C; detection wavelength, 215 nm; separation buffer, 40 mM sodium dihydrogen phosphate, and 100 mM sodium dodecyl sulfate (SDS) adjusted to pH 7.5. The influence of various parameters on the separation such as SDS c oncentration and the pH of the buffer were investigated. The method shows g ood repeatability, linearity and sensitivity. The robustness of this method was examined by applying a full factorial design to test the influence of the pH of the buffer, the SDS concentration and the buffer concentration.