Use of 2,6-dichloroquinone chlorimide for the spectrophotometric determination of halogenated derivatives of 8-hydroxyquinoline

Abstract

A spectrophotometric procedure is described for the determination of 8-hydroxyquinoline and three of its halogenated derivatives: 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol), 5,7-diiodo-8-hydroxyquinoline (iodoquinol) and 8-hydroxy-7-iodo-5-quinolinesulphonic acid (chiniofon). The proposed method involves the use of 2,6-dichloroquinone chlorimide as the chromogenic reagent. 8-Hydroxyquinoline produces a blue colour peaking at 595 nm and the other compounds yield a green-blue colour with maximum absorption at about 650 nm. The colours produced obey Beer's law and are suitable for the quantitative determination of the named compounds. The molar ratio of the reaction was established and a proposal for the reaction pathway is given. The procedure described was applied successfully to the determination of the named compounds in dosage forms and the results obtained were comparable to those obtained with official methods.