Effect of Capillary Rinsing Protocol on the Reproducibility of Separation in Capillary Electrophoresis with Indirect UV Detection

Capillary electrophoresis (CE) with indirect UV detection is an interesting analytical method for the analysis of drugs and pharmaceuticals. Good and reproducible capillary quality is needed to develop robust methods and to facilitate method transfer in CE. It is widely accepted that preconditioning procedures are indispensable in capillary electrophoresis in order to achieve reproducibility of migration times and peak areas. In order to explore different aspects of this technique, a set of experiments were performed using vigabatrin as a model drug. The effects of capillary rinsing between each run was investigated using basic (NaOH 0.1 M) and acidic (phosphoric acid 0.1 M)-wash cycles. The results of 10 consecutive injection of the model drug after each of the two wash cycles, reveal that more reproducible results obtained when acid-wash cycle was performed as a capillary conditioning protocol. The higher pH changes during basic-wash cycle and its effects on the characteristics of the capillary inner surface were suggested as a source of greater variation between consecutive runs.