J. Soc. Cosmet. Chem. 25, 535-544 (1974) ¸ 1974 Society of Cosmetic Chemists of Great Britain The thin layer chromatographic detection and determination of an imidazolidinyl urea ß preservauve antimicrobial D. S. RYDER* Synopsis--An ANTIMICROBIAL PRESERVATIVE of the IMIDAZOLIDINYL UREA type is detectable in a variety of complex cosmetic and toiletry formulations by TLC. The method is specific for the above type of preservative, even in the presence of a number of other antimicrobials. A ten-fold increase in sensitivity of the ninhydrin reacted zones is achieved when using TRANSMITTED UV LIGHT as compared to visible daylight colours. The antimicrobial is quantitatively determined in a moistu/'izing lotion with a relative standard deviation of 4-10 % using DENSITOMETRY. INTRODUCTION Cosmetics provide an ideal medium for the growth of microorgan- isms. The manufacturer must guard against the microbial contamination of his product during manufacture and storage and also against contamination by the consumer. Thus antimicrobial preservatives are added which are designed to be effective against a wide spectrum of microorganisms over a long period of time. * Analytical Services, Research Department, Ciba-Geigy (UK) Limited, Trafford Park, Man- chester. 535

536 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Many non-polar preservatives are in common use and several authors have reported tlc methods for their detection. K6nig (1) separated and identified 16 halogenated aromatics. Karlskind, Valmalle and Wolff (2) quantitatively estimated six halogenated aromatics in soap by means of tlc and spectroscopic methods. Graber, Domsky and Ginn (3) identified zinc omadine and five halogenated aromatics in personal care products. Hexa- chlorophane, tribromosalicylanilide and trichlorocarbanilide have been detected and quantitatively determined by Schwarze (4) using tlc and ion exchange procedures. In addition, Porcaro and Shubiak (5) developed a uv/ liquid chromatographic method for the estimation of hexachlorophane in nanogram quantities using a dianisate ester derivative. Wolf and Senionow (6) detected six halogenated aromatics in soap using High Pressure Liquid Chromatography, although Irgasan CFa and trichlorocarbanilide were not separated. Little has been reported of the more difficultly-detected and quantified non-aromatic, polar, hydrophilic antimicrobials, particularly of the imidazolidinyl urea type. The first commercial member of this family is Germall 115.* This preservative is claimed to be a broad spectrum antimicrobial which is non- toxic, non-irritating and is particularly effective in emulsions and protein- containing formulations. It concentrates in the microbial supporting aqueous phase and its efficiency is not impaired by the presence of non-ionic emulsifiers and proteins. For quality control purposes and for the identification of antimicrobials in unknown formulations, it was necessary to develop a rapid and specific identification and quantification procedure for imidazolidinyl urea in a wide variety of personal care products. Because of the complexity of the formula- tions to which this preservative may be added, i.e. lotions, creams, hair conditioners, shampoos, deodorants etc., a comprehensive colorimetric method was impracticable. Thus tlc was used, since no sample preparation was necessary and the method was applicable to new products without change in the procedure. EXPERIMENTAL Apparatus Thin layer plates: 20 x 20 cm 0.25 mm Silica gel F,254 (Merck) used as re- ceived without further activation. * Sutton International, Boyelle, N.J., U.S.A.