ABSTRACT
First derivative and dual-wavelength spectrophotometric methods were used in the quantum yield determination of the photochemical decomposition reactions of three thiazide diuretics (chlorothiazide, hydrochlorothiazide and trichloromethiazide) in ethanolic solution. The radiation absorbed by the compounds was measured using iron(III) oxalate actinometry based on absorption spectrophotometry. An apparatus is described in which the drugs were irradiated in quartz cuvettes cooled by water in a stand built on a magnetic stirrer. The wavelength region available to the reaction cuvette was restricted to 313 nm with chemical potassium chromate filter solutions and a Corning filter plate. Chlorothiazide proved to be more photostable than hydrochlorothiazide and trichloromethiazide in ethanol.
Subject(s)
Chlorothiazide/chemistry , Hydrochlorothiazide/chemistry , Sodium Chloride Symporter Inhibitors/chemistry , Spectrophotometry, Ultraviolet/methods , Trichlormethiazide/chemistry , Diuretics , Drug Stability , Kinetics , LightABSTRACT
Ethanolic solutions of three thiazide diuretics, chlorothiazide, hydrochlorothiazide and trichlormethiazide, were irradiated with a high-pressure mercury lamp. The products were isolated and their first-derivative UV spectra in ethanol were recorded and compared to those of the parent compounds. The determination of the parent compounds in the presence of the decomposition products was carried out at wavelengths near 220 nm using the zero-crossing technique. Three reversed-phase HPLC methods were also developed for the analysis of the parent compounds. In parallel analyses of the reaction mixtures a good correlation was achieved between these two methods in the determination of hydrochlorothiazide and trichlormethiazide while there was greater variation in the results of chlorothiazide.
Subject(s)
Sodium Chloride Symporter Inhibitors/analysis , Chlorothiazide/analysis , Chlorothiazide/chemistry , Chromatography, High Pressure Liquid , Diuretics , Hydrochlorothiazide/analysis , Hydrochlorothiazide/chemistry , Light , Photolysis , Sodium Chloride Symporter Inhibitors/chemistry , Sodium Chloride Symporter Inhibitors/radiation effects , Spectrophotometry, Ultraviolet , Trichlormethiazide/analysis , Trichlormethiazide/chemistryABSTRACT
A simple isocratic high-performance liquid chromatographic method for monitoring the photodecomposition of chlorothiazide in ethanolic solution is described. A 125-mm RP-18 column and an aqueous mobile phase containing 10% methanol and 2% acetic acid were used. The flow-rate was 1.0 ml/min and the UV detector wavelength 265 nm. Samples of 0.2 ml were taken from the reaction vessel and diluted 10-fold. The external standard method was used in the quantitative determinations. The decomposition appeared to proceed according to first-order kinetics. When the solutions were saturated with oxygen, the decomposition was greatly inhibited.
