Development and Validation of a Reversed-Phase High-Performance Liquid Chromatographic Method for the Simultaneous Determination of Amiloride Hydrochloride, Atenolol, Hydrochlorothiazide, and Chlorthalidone in Their Combined Mixtures

A high-performance liquid chromatographic method was developed for the simultaneous determination of 2 ternary mixtures containing amiloride hydrochloride, atenolol, hydrochlorothiazide, and chlorthalidone used in hypertension therapy. The use of cyanopropyl column results in satisfactory separation of both mixtures. The mobile phase consisted of 10 mM KH(2)PO(4) buffer (pH 4.5) and methanol in a ratio of (75 + 25\% v/v), at a flow rate of 1 mL/min. UV detector was operated at 275 nm. Calibration graphs were linear in the concentration ranges of 2-10, 20-200, 10-100, and 5-50 mu g/mL for amiloride hydrochloride, atenolol, hydrochlorothiazide, and chlorthalidone, respectively. Intraday and interday precision values (relative standard deviation) were <1.13 for mixture I (amiloride hydrochloride, atenolol, chlorthalidone), and <0.93 for mixture II (amiloride hydrochloride, atenolol, hydrochlorothiazide). The method was successfully applied for the determination of the 2 combinations in laboratory-prepared mixtures and commercial pharmaceutical formulation with high accuracy and precision. Statistical comparison of the results with those of the published methods showed excellent agreement and indicates no significant difference between them.