| Abstract: | Abstract A new, sensitive colorimetric method has been described for the quantitative determination of six N-substituted phenothiazines. the method depends on the formation of stable phenothiazine free radical by the use of 2-iodoxybenzoate as chromogenic reagent. the drug in 50% sulphuric acid is treated with reagent (5×10?4 M). the produced red or purple color possesses characteristic absorption maximum for each of the drugs tested. Beer's law is obeyed over the concentration range 2-30 μg.ml?1 with apparent molar absorptivities ranging from 9.4-12.4×10?3 for the studied phenothiazine derivatives. the average % recovery is 99.5±0.96 - 101.6±1.01. the method was applied successfully to the microdetermination of promazine. HCl, chlorpromazine, HCl, promethazine. HCl, perphenazine, levomepromazine HCl and mesoridazine besylate either in pure form or incorporated in their representative pharmaceutical preparations. the stoichiometry of the reaction was assumed and a reaction mechanism was suggested. the precision of the assay was comparable with the official ones. |
