Colorimetric determination of some hydrazone derivatives

A simple and rapid colorimetric method was described for the determination of isocarboxazid, iproniazid phosphate and phenylhydrazine hydrochloride. The method depended on the use of 2-iodoxybenzoic acid, as an oxidant in 50% w/v orthophosphoric acid to oxidize chlorpromazine HCl to chlorpromazine free radical, which absorbs at 530 mm. This red free radical was rapidly and quantitatively reduced by the investigated compounds to the colorless chlorpromazine. The decrease in absorbance was found to be directly proportional to the quantity of each compound studied, and this forms the basis for the quantitative estimation of micro-quantities of the investigated compounds

Titrimetric and spectrophotometric titration of some pharmaceutical important thiol compounds using 2,6-dichlorophenol-indophenol

Two procedures were adopted for determination of three pharmaceutical compounds containing thiol group; namely, D-penicillamine, N-acetylcysteine and captopril, by 2,6-dichlorophenol-indophenol [DCPIP]. In the first, the drugs are treated with a known and excessive volume of 1 x 10-3 M DCPIP and after 5 minutes the surplus is determined by titration with standard L-ascorbic acid. In the second, the drugs are titrated with 5 x 10-4 M solution of DCPIP with spectrophotometric end-point detection. The stoichiometry of the reaction is assumed and a reaction mechanism is suggested. The methods have been applied to the analysis of pharmaceutical preparation containing these drugs and the results obtained compared favorably with those from the pharmacopoeial methods. The methods are simple, accurate and precise

Spectrophotometric determination of captopril in dosage form via charge-transfer complexes

Two simple and sensitive spectrophotometric methods for the assay of captopril have been presented. The first is based on the reaction of captopril with iodine to give a molecular charge-transfer complex. The second method depends on the formation of a highly colored stable radical anion between captopril and 7,7,8,8-tetracyanoquinodimethane [TCNQ] as a pi-electron acceptor. The molecular ratios of the reactants in the complexes as well as the experimental conditions leading to maximum charge-transfer b and s have been studied. Beer's Law is obeyed over captopril concentration range of 2-8 mug.ml -1 by iodine method and 0.32-3.2 mug.ml -1 by TCNQ method. The proposed procedures have been applied successfully to the analysis of captopril tablets and the results are in agreement with those of official methods