370 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Stevenson, D. G. The Mechanism of Detergent Action (1951) (Ph.D. Thesis, London University) J. Textile Inst. 4,4, T12 (1953) Lawrence, A. S.C. Nature 183 1491 (1959) Faraday Soc. Discussions 25 51 (1958) Stevenson, D. G. J. Textile Inst. 4,2 T194 (1951) Stanley, J. J. Phys. Chem. 58 533 (1954) Kruyt, H.R. Colloid Science 1 Ch. 6 (1952) (Elsevier, London) McBain, J. W., Colloid Science 21 (1950) (Heath, Boston) Sawyer, W. M., and Fawkes, F.M. J. Phys. Chem. 62 159 (1958) Niven, W.W. Fundamentals of Detergency 4 (1950) (Reinhold, New York) Wark, E. E., and Wark I.W. Nature 14,3 856 (1939) Stevenson, D. G. J. Soc. Dyers Colourists 68 57 (1952) GAS-LIQUID CHROMATOGRAPHY AND THE PERFUMER D. HOLNESS, B.A.* A lecture delivered before the Society on 2$rd February 1961. Gas-liqukl chromatogral•hy is an efficient sel•aration technique which can simlflibj the l•er•umer's stmlies of coml•lex raw materials. Its alrea•ly numerous al•l•lications are liste•l, anal the nee•l for careful choice of working con•li•ions is stresse•l. Examlfles are given of quantitative analyses aml of klen•ifications of essential oils of similar tyl•es. THE TERM "chromatography" covers a group of closely related separation techniques, all based on partition between two phases, one fixed and one moving. Chromatographic methods are outstanding in efficiency, and have the additional merit of working under conditions which permit the safe handling of many relatively unstable compounds. Gas-liquid chroma- tography, distinguished by having a gas as mobile phase and a liquid as stationary phase, is applicable to substances with appreciable vapour pressures at moderate temperatures. Perfumers frequently work with mixtures of uncertain composition (notably the essential oils) and their raw materials have odours, a property which implies some degree of volatility. Consequently chromatography has obvious applications in this field, with gas-liquid chromatography as the method of choice. The value of gas-liquid chromatography to the perfumer lies mainly in its ability to simplify his studies of mixtures. It is by no means the answer to all his problems, nor is it a sort of "artificial *Proprietary Perfumes, Ltd., London, S.E.1.

GAS-LIQUID CHROMATOGRAPHY AND THE PERFUMER 371 nose" as some fanciful writers have claimed. The trained nose is a detector of a far higher degree of organization than any known gas-liquid chroma- tography detector. If geraniol, for instance, is fed into a gas-liquid chromatography detector, the response tells only that some material is there. By contrast, the perfumer's nose yields the identification "geraniol", indi- cating the structure down to stereochemical details! Likewise, the per- fumer can name the constituents of simple mixtures which the gas-liquid chromatography detector cannot by itself show to be mixtures. Even the best nose, however, has its limitations. It can identify only compounds of which it has had previous experience. It cannot, like the gas-liquid chromatography column, resolve mixtures into separate lots, each composed of molecules of a single kind, for examination independently of each other. It grows less sure as the complexity of the mixture increases and it is hampered by the existence of blends--so much sought after in creative perfumery--with unified odours. In quantitative evaluations the nose is an inferior performer. Furthermore, the perfumer's assessment of a material is subjective, and is therefore unjustly regarded by unskilled observers as a mere opinion which they are entitled to dispute in the absence of supporting evidence. Perfumers have long looked for help from techniques like distillation and chemical analysis, and it is hardly surprising that nowadays many of them welcome the aid of gas-liquid chromatography, both on the analytical scale and on the preparative scale in combination with other modern instru- ments like the infra-red and mass spectrometers. The applications of gas-liquid chromatography to perfumery have already become so numerous that it would take too long to describe them all fully. I therefore propose only to list the ones I know of, and then to discuss in greater detail a few subjects selected to illustrate both the advantages and the limitations of this method. Gas-liquid chromatography can be used to help perfumers (a) In quality control for identification of essential oils by comparing their chromatograms with standard trace-patterns for comparisons of the proportions of isomers in "mixed" synthetics such as the ionones for checking the impurities present in synthetics and isolates for seeking evidence of suspected admixture or adulteration for checking compounded perfumes for investigating the causes of observed odour differences and odour changes in all kinds of raw materials for direct quantitative determinations of selected single constituents of essential oils and other raw materials.