Simultaneous determination of hydrochlorothiazide and several inhibitors of angiotensin-converting enzyme by capillary electrophoresis

A capillary electrophoresis method was developed for the simultaneous determination of hydrochlorothiazide and several angiotensin-converting enzyme (ACE) inhibitors: enalapril, lisinopril, quinapril, fosinopril, ramipril, and cilazapril. The most critical parameter is the pH of the running buffer. Separation was performed on a fused-silica capillary (52 cm total length×75 μm I.D.) using a sodium phosphate buffer (pH 7.25; 100 mM). The method was successfully applied to the quantitative determination of these compounds in their corresponding pharmaceutical formulation. The method was validated in terms of linearity of response, reproducibility and accuracy.