Validation of the RP-HPLC method for analysis of hydrochlorothiazide and captopril in tablets

A rapid and sensitive reverse-phase high performance liquid chromatography (RP-HPLC) method with ultra-violet (UV) detection for a routine control of hydrochlorothiazide and captopril in tablets was developed. The chromatographic system Hewlet Packard 1100 consisted of a HP 1100 pump, HP 1100 UV-VIS detector and HP ChemStation integrator. The samples were introduced through a Rheodyne injector valve with a 20-muL sample loop. The isocratic system consisted of a Beckman Ultrasphere ODS 4.6 mm x 15 cm, 5-mum-particle column and a mobile phase containing methanol/water (45:55 v/v). The pH of the mobile phase was adjusted to 3.8 with 85% ortophosphoric acid. Quantitation was accomplished using the internal standard method. At the selected conditions, the other excipients of the tablets did not interfere in the assay of active substances. The developed RP-HPLC method was validated, so linearity, precision, accuracy, robustness, limit of quantitation and limit of detection were investigated. For the robustness test, three factors were considered: the composition of the mobile phase, the pH of the mobile phase, and temperature. With the aid of response surface metodology (RSM), it was possible to precisely define the robustness of the method.