J. Soc. Cosinefir Chemists 19 213-223 (1968) ¸ lo68 Socuty o! Cosmetic Chemistt of Great Britain Estimation of hexachlorophane cosmetic products in A REPORT BY THE METHODS OF ANALYSIS SUBCOMMITTEE OF THE SOCIETY OF COSMETIC CHEMISTS OF GREAT BRITAIN Syn0psis•Methods for analysing hexachlorophane in toiletries and cosmetics are reviewed, and discussed. Preliminary experiments with uv absorption methods indicated that the differ- ential absorption method was preferable to the one measuring absorption at fixed wave- lengths, which could suffer interference from extraneous and irrelevant absorption. Interlaboratory collaborative tests have been carried out on certain toilet preparations, viz. alcoholic solutions, talcs and soaps, containing hexachlorophane at levels between 0.2 and 2 •o, using the differential absorption method of Elvidge and Peutrell. Results show that the method is sufficiently accurate and specific for the determination of hexachlorophane in these preparations. INTRODUCTION Hexachlorophane is used in a large number of cosmetic and toiletry products. It functions as a germicide, bactericide or deodorant in products such as talcs, soaps, deodorant and/or antiperspirant preparations, tooth- pastes, etc., and is generally used at a concentration between 0.01% and 2.0%. The Methods of Analysis Subcommittee of the Society of Cosmetic Chemists of Great Britain has reviewed existing methods for estimating hexachlorophane to find a simple specific method suitable for estimating this material in toilet preparations. REVIEW OF POSSIBLE METHODS Published methods can be grouped as follows: (1) Titration methods. 213

214 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) Colorimetric methods. (3) Measurement of absorption at specific wavelengths. (4) Differential absorption measurements. (5) Gas chromatography. (6) Determination of organic chlorine. Titration methods Potentiometric titration (1) is suitable for the pure material but not for hexachlorophane in a product. High frequency titration techniques (2) have been used for various phenols but they require special equipment. Colorimetric methods Several colorimetric methods have been used. •t Amino antipyrine-potassium ferricyanide This method is widely used and was first published by Gottlieb and Marsh (3). Mohler and Jacob (4) considered it to be the most sensitive and accurate method available, whereas Larson (5) and Lord, McAdam and Jones (6) reported that results were unreliable. The sensitivity of the reaction is pH dependent and the result is not specific for hexachlorophane. Achmeteli (7) overcame the interference from methyl salicylate in toothpaste by using methylene blue instead of potassium ferricyanide, but anionic detergents also react with methylene blue and must first be removed. 2.6 Dibromoquinone chloroimide This method, often known as the Gibbs method (8), is based on the formation of a dibromo-indophenol dye which can be estimated colori- metrically. It has been adapted by Singer and Stern (9) for the determina- tion of bisphenols such as hexachlorophane, but is not specific. Nitrosophenol Gibbs (10) examined the reaction of phenols with nitrous acid and the [ormation of coloured nitroso compounds. Stroughton (11) developed a method for the preparation of nitroso compounds with nitric and sulphuric acids at 100øC, and their rearrangement in the presence of excess alcoholic ammonium hydroxide to produce a highly coloured quinonoid radical. Lykken, Treseder and Zahn (12) modified this method and used sodium nitrite in acetic acid to form the nitrosophenol at room temperature.