Captopril/Hydrochlorothiazide

The present investigation demonstrates the potentials of ethyl-propiolate (EP), a novel derivatizing reagent for thiols. To the best of our knowledge this is the first systematic study of EP in analytical chemistry. The reaction was investigated under flow conditions using sequential injection (SI) analysis and UV detection at 285 nm. The reaction kinetics was affected by parameters such as the pH, the concentration of EP and the temperature and was thoroughly examined exploiting stopped-flow experiments. Cysteine (CYS) and captopril (CAP) were selected as model thiolic compounds in terms of chemical structures. Finally, the applicability of EP as a derivatization reagent for analytical purposes was demonstrated by the development and validation of a novel automated assay for the determination of CAP in pharmaceuticals.

A simple, rapid, accurate, precise, and sensitive colorimetric method for the determination of captopril (CAP) in bulk sample and in dosage forms is described.The method is based on oxidation of the drug by potassium permanganate in acidic medium and determination of the unreacted oxidant by measuring the decrease in absorbance for 5 different dyes; methylene blue (MB); acid blue 74 (AB), acid red 73 (AR), amaranth dye (AM), and acid orange 7 (AO) at a suitable λ_max (660, 610, 510, 520, and 485 nm), resp.Regression anal. of Beer's plots showed good correlation in the concentration ranges (0.4-12.5, 0.3-10, 0.5-11, 0.4-8.3 and 0.5-9.3 μg ml^-1), resp.The apparent molar absorptivity, Sandell sensitivity, detection, and quantitation limits were calculatedFor more accurate results, Ringbom optimum concentration ranges were 0.5-12, 0.5-9.6, 0.6-10.5, 0.5-8.0, and 0.7-9.0 μg ml^-1, resp.The validity of the proposed method was tested by analyzing in pure and dosage forms containing CAP whether alone or in combination with hydrochlorothiazide.Statistical anal. of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of CAP in pure form and in pharmaceutical preparationsAlso, the stability constant was determined and the free energy change was calculated potentiometrically.