Simultaneous determination of triamterene and hydrochlorothiazide in tablets using derivative spectrophotometry

A quick and accurate method for determining triamterene and hydrochlorothiazide in complex drugs of diuretic activity by using first-derivative (D1) and second-derivative (D2) spectrophotometry was developed. The zero-crossing technique was employed in measurements, using D1 at lambda = 240.9 nm and D2 at lambda= 278.2 nm for determining triamterene and D1 at lambda = 255.7 nm and D2 at lambda = 283.2 nm for hydrochlorothiazide. The linear relationship between the values of derivatives and analyte concentrations are maintained for concentrations from 2.40 microg x mL(-1) to 12.00 microg x mL(-1) for triamterene and from 1.25 microg x mL(-1) to 6.25 microg x mL(-1) for hydrochlorothiazide. LOD for triamterene was 0.90 microg x mL(-1) or 1.02 microg x mL(-1), while LOQ was 2.73 microg x mL(-1) or 3.08 microg x mL(-1). The corresponding values for hydrochlorothiazide were: LOD 0.25 microg x mL(-1) or 0.17 microg x mL(-1) and LOQ 0.77 microg x mL(-1) or 0.51 microg x mL(-1) depending on the derivative used. The determination results of drug constituents are of high accuracy, percentage recovery ranging from 97.17% to 99.74% for triamterene and from 102.44% to 102.64% for hydrochlorothiazide, and good precision. The computed values of RSD are smaller than 2.73% for triamterene and below 1.63% for hydrochlorothiazide. Selectivity and sensitivity of the developed method are satisfactory.