A novel spectrophotometric determination of some phenothiazines involving iodine monochloride from chloramine-T with iodine.

Malledevarapura D Gowtham, Mysore S Yogendra Kumar, Mahadeshwarabetta A Sathish, Giddappa Nagendrappa

Index: Arch. Pharm. (Weinheim) 337(11) , 605-14, (2004)

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Abstract

A novel, simple, sensitive spectrophotometric method is proposed for the determination of five phenothiazines. Chloramine-T with iodine in acetic acid produces iodine monochloride which oxidizes phenothiazines to absorbing cations. Those would associate later with unreacted ICl to form an ion pair, [Ph+] [ICl-(2)] in hydrochloric acid medium. These appear to provide exceptional color stability to the systems. A probable mechanism along with experimental stoichiometry and stability constants of such ion pairs is indicated. The method is not only successful in stabilizing the color of the systems, but also in making a unique observation of two regions of concentration of phenothiazines adhering separately to Beer's law. The results obtained from the analyses of pure samples and their drug formulations in both regions of concentration are comparable with those obtained either with a reported titrimetric method or with a British Pharmacopoeia (B.P.) UV-spectrophotometric method. The conditions required for the quantitative determination of phenothiazines are described and related analytical parameters are also calculated.