Statistical optimization of a reversed-phase liquid chromatographic methodfor the analysis of amiloride and hydrochlorothiazide in tablets

A method has been developed for the separation of hydrochlorothiazide and a miloride by high-performance liquid chromatographic (HPLC) method on a C-18 column with detection at 280 nm. The optimal conditions of separation were determined with the aid of 'window diagram' technique of Laub and Purnell. The effect of simultaneously varying the pH, proportion aqueous acetic aci d and methanol in the mobile phase were studied to optimize the separation. ,A response surface diagram was used to optimize the experimental condition s for the separation. The mobile phase composition that provides an accepta ble resolution hydrochlorothiazide and amiloride in a short elution time is water:methanol (60:40) and pH 3.2 (pH adjusted to 3.2 with CH3COOH). A met hod is applied for the quantitative analysis of Moduretic((R)) tablets (Mer ck Sharp & Dokme International). The powdered tablets are extracted with me thanol, containing caffeine as the internal standard; and assayed by compar ison of peak areas after liquid chromatography. (C) 2000 Elsevier Science B .V. All rights reserved.