Development and validation of a bioanalytical method for the quantification of diltiazem and desacetyldiltiazem in plasma by capillary zone electrophoresis.

A CZE method for the quantification of diltiazem and desacetyldiltiazem in plasma was developed and validated. Separation was accomplished at pH 2.5 in a 0.044 M phosphate buffer. Sample preparation was performed by liquid-liquid extraction and no interferences with plasma compounds were detected. The calibration graph is linear over the range 5-250 ng/ml with verapamil as internal standard. The precision and accuracy are better than 13% at 5 ng/ml, and better than 10% between 10 and 250 ng/ml. The long-term reliability of the CZE system was checked over a 3-month period. The CZE method is a useful alternative to the already established HPLC method.