Simultaneous estimation of captopril and hydrochlorothiazide in combined dosage forms

Aim: This work deals with the simultaneous determination of captopril (CAP) and hydrochlorothiazide (HZ) in two-component solid dosage form, without prior separation, by three different techniques (simultaneous equation, absorbance ratio method, and first-order derivative method). Materials and Methods: This work was carried out on Shimadzu electron UV1800 double-beam UV-Visible spectrophotometer. The absorption spectra of reference and test solutions were carried out in 1 cm matched quartz cell over the range of 200-400 nm. Methanol and distilled water are used as solvent. Results: The first method is the application of simultaneous equation. Where the linearity ranges for both the drugs were 5-35 μg/ml. The second method is the determination of ratio of absorbance at 271 nm, the maximum absorption of HZ and isobestic wavelength 209 nm, the linearity ranges for both the drugs were 10-120 μg/ml The third method is the first-order derivative method, where the CAP shows wavelength at 222 nm and HZ shows at 340 nm, and the linearity ranges for CAP and HZ were 1-30 μg/ml and 1-40 μg/ml, respectively. The proposed procedures were successfully applied for the simultaneous determination of both the drugs in commercial tablet preparation. The validity of the proposed methods was assessed by applying the standard addition technique where the percentage recovery of the added standard was found to be 99.52±0.214 and 99.00±0.165 using the simultaneous equation method, 99.76±0.684 and 99.58±0.279 using the graphical absorbance ratio method, and 99.45±0295 and 99.21±0.678 using first derivative method, for CAP and HZ, respectively. Conclusion: The proposed procedures are rapid, simple, require no preliminary separation steps, and can be used for routine analysis of both drugs in quality control laboratories.