258 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS CHEMICAL ANALYSIS IN THE COSMETIC INDUSTRY S. J. BUSH, F.R.I.C.* Based on a lecture delivered before the Society on 14th November 1988 The problems and functions oi the non-routine analyst in the cosmetic industry are briefly discussed and some of the methods at his disposal are indicated with examples. TRE DICTIONARY defines analysis as "a resolving or separating of a thing into its elements or components", a definition which is sound enough except that analysis in the technical sense often stops short of this ideal. It does, however, provide a starting point for a rough classification of analysis into two main divisions according to the purpose for which it is undertaken. The first kind of analysis fits squarely into our definition. The analyst does not know the composition of the sample and he sets out to resolve it into its components--rather like the small boy who takes the clock to pieces to see what makes it go. The second type of analysis is that in which the analyst knows what the composition of the sample should be and he is concerned only with checking the composition, wholly or in part. Here he behaves more like the little boy's father who takes the clock to pieces to make sure that all the parts are there. The second class of analysis, often referred to as "quality control", is, of course, of the utmost importance in the cosmetic or any other industry, but the main purpose of this paper is to deal with non-routine analysis and the examination of unknowns. The analysis of unknowns, whatever their source, involves all the usual techniques of analysis and often some unusual ones, the employment of thought processes of a somewhat specialized--one might almost say tortuous ---kind, and the ability to adapt and modi[y a plan as the analysis unfolds. It also involves a considerable amount of research into methods. Each sample is a problem in its own right and there is no hard and fast scheme or set of rules which can be followed and which will with certainty lead one to the identity of every ingredient. In the case of strictly competitive samples the analyst will have special- ized knowledge which will enable him to formulate a scheme which will bring to light, fairly rapidly, the most likely components and will at the * County Laboratories Ltd., Startmore, Middx.

CHEMICAL ANALYSIS IN THE COSMETIC INDUSTRY 259 same time indicate the presence of any unusual materials. The identification and subsequent extraction or determination of these unusual substances will, however, constitute a separate problem to be dealt with after the "basic analysis" has been done. With products which are not strictly competitive or which are outside the analyst's normal field a good deal of preliminary thought and reading may have to be devoted to planning a likely approach. In such cases an adequate patent survey of the subject is often of great assistance. Much of the work of the non-routine analyst consists of research into methods of analysis and the application or modification of general methods to suit particular problems. The determination of individual components of a mixture is usually required at some stage, and new methods and new techniques are constantly being devised to make the process easier and quicker. Chromatography can no longer be described as a new technique and it now has applications in almost all branches of analysis. Paper chromato- graphy is a rapid and useful technique for the separation of certain closely similar materials from a few micrograms of sample. Glycerol can be separated from other polyalcohols in this way, using water-saturated n-butanol as developer and ammoniacal silver nitrate as detector, the zones showing as black spots. The spots can be eluted with water and the glycerol determined by a modification of the periodate oxidation method •. Hexa- chlorophene and other antiseptics, and thioglycollic and thiolactic acids can also be detected by paper chromatography 2, while considerable use of this method has been made for the separation and identification of dyes and colouring matters. An ingenious method of constantly changing the composition of the developer has been described by Franks', who uses paper chromatography for anionic surface-active agents. The examination of mixtures of oils and fats as occur, for instance, in the oil phase of an emulsion has always been a difficult task if the mixture is at all complex. The determination of the usual constants is still a standard procedure of great utility, but it is particularly useful to be able to separate physically at least one fraction of the fats. This is possible by using column chromatography as described by Williamst when all components of the unsaponifiable matter, except hydrocarbons, are absorbed on the column and the hydrocarbons may be recovered quantitatively from the eluate. In many cases this method can be applied to fat mixtures without separating the unsaponifiable matter, though control tests with known mixtures should first be run. The details are as follows: Chromatographic separation of hydrocarbons. Prepare a column (about 8 cm long by 1 cm in diameter) of chromato-