Spectrophotometric methods for the simultaneous estimation of losartan potassium and hydrochlorothiazide in tablet dosage forms

Aim: This work deals with the simultaneous determination of Losartan potassium (LSP) and Hydrochlorothiazide (HZ) in a binary mixture form, without prior separation, by three different techniques. Materials and Methods: The present 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. Standard gift sample of LSP and HZ were obtained from Torrent pharmaceuticals Ltd, Baddi, Himachal Pradesh. Combined LSP and HZ tablets were purchased from local market. Methanol from Merck Ltd. and distilled water are used as solvent. Results: The first method is the application of simultaneous equation. Where the linearity ranges for LSP and HZ were 5-25 μg/ml and 1-20 μg/ml, respectively. The second method is the determination of ratio of absorbance at 272 nm, the maximum absorption of HZ and isosbestic wavelength 266.5nm, the linearity ranges for LSP and HZ were 5-80μg/ml and 1-25μg/ml respectively. The third method is the first order derivative method, where the linearity ranges for LSP 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 99.06±1.210 and 99.30±1.159 using the simultaneous equation method, 99.66±0.573 and 99.95±0.272 using the graphical absorbance ratio method and 99.64±0.301 and 99.91±0.614 using first derivative method, for LSP and HZ respectively. Conclusions: 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.