Statistical optimization applied to simultaneous determination of maprotiline, desipramine, and moclobemide by capillary zone electrophoresis

A method of Capillary Zone Electrophoresis (CZE) for separation of three most-frequently prescribed antidepressants in the market: maprotiline, desipramine, and moclobemide was developed. The proposed method is fully validated for a ternary laboratory mixture but it is also suitable for individual determination of the investigated components in pharmaceutical dosage forms. Since the preliminary investigations did not show complete separation because of close migration time of desipramine and maprotiline, a complete set, 2(3) experimental design was applied. All the factors that affect separation as well as their mutual interactions were investigated. Voltage, temperature of capillary and the pH of phosphate buffer were independent variables or factors to be investigated in two levels. Applying response surface methodology, from experimental points the appropriate graphs were constructed and optimal chromatographic conditions for the separation were defined. The optimum conditions were: running voltage of 20kV, phosphate buffer (pH = 2.35), temperature 25 degrees C, and UV detection at 200nm. An uncoated (fused silica) capillary (50 mu m i.d.) with a total length of 50cm and a distance of 47cm between the injection and detection points was used.