Separation of promethazine and thioridazine using capillary electrophoresis with end-column amperometric detection.

Promethazine and thioridazine were separated and detected by capillary electrophoresis with end-column amperometric detection. The influence of pH value on oxidation potential, the peak current and the resolution were studied and the following conditions was selected: 0.03 M Na2HPO4 and 0.015 M citric acid at pH 3.0, detection potential at 1.10 V. The detection limits of these two substances were in the range of 10(-8) mol/l. The linear range spanned two to three orders of magnitude. This method was applied to the detection of promethazine and thioridazine spiked in urine.