Abstract
The internal standard method is a versatile procedure that avoids misleading results caused by the instability of the chromatographic system or inexperienced workers. It is an effective way to judge the accuracy of any obtained data. As the detector responses of chlorzoxazone (CZN) resemble those of candesartan (CDZN) and hydrochlorothiazide (HCTZ), CZN was employed as an internal standard. Herein, a simple chromatographic method was established for quantification of CDZN and HCTZ. Isocratic elution was conducted using 1% premixed acetonitrile/formic acid (7:3 v/v) at a 0.8 mL/min flowrate. The separation of the three components was maintained using the universal 20 mL loop, and for further simplicity in application, the analysis was optimized at 25 degrees C. CDZN, HCTZ, and CZN were simultaneously monitored and quantified at 270nm. The method developed here complies with all the validation limits according to the British Pharmacopoeia (BP), United States Pharmacopoeia (USP), and the guidelines of the International Council For Harmonisation (ICH). The method proved to be linear in the range of 6.4 to 25.6 mu g/mL and 5.0-20 mu g/mL for CDZN and HCTZ, respectively, while the quantitation detection limits were less than 1.0 mu g/mL for both.