The simultaneous determination of hydrochlorothiazide and cilazapril in tablet formulation by high performance liquid chromatography

A liquid chromatographic method is presented for the determination of cilazapril and hydrochlorothiazide in inhibace-plus tablet. The liquid chromatographic analysis of the binary mixture of hydrochlorothiazide and cilazapril has been conducted by using mu-Bondapak C-18 as reversed phase column and isocratic metanol - pH 4.0 phosphate buffer (70:30) (v/v) as mobile phase. Phenobarbital has been used as internal standard. The drug substances have been determined with variable wavelength UV spectrophotometric detector at 209 nm. The retention times are respectively 2.56; 3.53 and 5.30 min at 1.0 ml/min flow rate for hydrochlorothiazide, phenobarbital and cilazapril. The linear range of determination for hydrochlorothiazide and cilazapril is 10-30 mu g/mL and 5-15 mu g/mL, respectively. The method has been applied to commercially available tablet and the results have been statistically compared with those obtained by a derivative spectrophotometric method using t- and F- tests at 95 % confidence level.