TLC STUDY OF AN ANTIMICROBIAL PRESERVATIVE 541 due to chromatography was examined. A two-dimensional chromatogram was carried out using the solvent chloroform-methanol-acetic acid-water (50: 30: 10: 10) in both directions. All the components were found to lie in a diagonally straight line, showing that no new components were formed during the chromatographic run. In addition, solutions kept for several days showed no detectable decomposition compared to freshly-prepared solu- tions. The detection of imidazolidinyl urea when added to several cosmetic and toiletry products was attempted. These products included a moisturiz- ing lotion containing fifteen ingredients, some of which were themselves complex mixtures and known to include an aliphatic amine, a mixture of parabens, two dyes, a lanolin product, an emulsifier, long chain alcohols and esters, poly hydroxy compounds and aloe, polysaccharides, proteins, amino acids and vitamins. An egg shampoo was also tested, as unlike some anti- microbials, the efficiency of imidazolidinyl urea is not impaired by the presence of proteins. The other products tested were, a deodorant foam bath, a hand cream, a squeeze-on deodorant, a roll-on deodorant and an aerosol deodorant (Fig. 1). Imidazolidinyl urea was successfully detected down to at least 0.1% in all the products tested and only the roll-on deodorant and the aerosol deodorant exhibited any distortion of the preservative zones. The preservative was easily detected in the presence of other anti- microbials (Table II), including parabens with which it is recommended for joint use, as a synergistic effecl in efficiency has been observed. The detection system was specific for the imidazolidinyl urea type of antimicrobial when compared with other antimicrobials and additives, as none of those tested revealed a similar distinctive coloration in uv light, even though a number reacted with ninhydrin to form colours visible in daylight. Quantitative Although for routine quality control, a simple, visual comparison of spots with the appropriate standard spots is both rapid and sufficiently accurate, a more precise densitometric determination was also investigated. For all quantitative work, the sample was run with replicate spots alternately spaced with standard solutions, which consisted of the 'blank' product doped with known quantities of imidazolidinyl urea. The chromatographic conditions were as for the previous qualitative work.

542 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS I 2 3 4 5 6 Figure 1. Diagram of the detection of imidazolidinyl urea type (Germall 115) added to personal care products. System: pre-coated silica gel flow solvent = chloroform-methanol-acetic acid-water (50: 30: 10: 10) detection = nin- hydrin, viewed by transmitted uv light 366 rim. 1 = Germall 115 2 = hand cream 3 = foam bath 4 = moisturizing lotion 5 = egg shampoo 6 = deodorant. The main difficulty encountered in achieving reproducible results is in obtaining a regular and easily definable baseline. This in turn is due to the background colour on the plate which varies in the direction of the solvent flow. It was thought that adding ninhydrin to the flow solvent might improve the uniformity of the background colour and also remove errors due to uneven spraying. Unfortunately the reverse was found to be the case, the background intensity and variance being increased using this procedure. A partial answer to the problem was achieved by drawing a pencil line approximately 2 cm above the line of the imidazolidinyl urea spots and a line parallel to this through the origins of the spots. This enabled a base line for each applied spot to be drawn on the graph, joining the responses of the two pencil lines, i.e. before and after the Germall peaks. The maximum peak