j. Soc. Cosmet. Chem., 33,407-420 (December 1982) Cosmetic analytical chemistry--coming of age IRA E. ROSENBERG, Clairol Incorporated, 2 Blachley Road, Stamj•rd, CT 06922. Received October 28, 1982. INTRODUCTION The last 10 years have seen a rapid growth in both the activity and the importance of the analytical laboratories in the cosmetic industry. Two factors seem to have spurred this change. The first has its base in the increased types of raw materials available to cosmetic chemists. The fact that the 3rd Edition of the C.T.F.A. Ingredient Dictionary now contains 3,400 entries is a poignant reminder of progress in this area. The second has roots in the diversity of the analytical tools with which cosmetic laboratories are equipped nowadays. Advanced instrumentation coupled with microprocessor technol- ogy has allowed the researcher to probe more critically into the quality of supplied raw materials and formulated finished products. Techniques such as nuclear magnetic resonance spectroscopy (NMR), high pressure liquid chromatography (HPLC), mass spectroscopy (MS), and capillary gas chromatography (CGC) are standard equipment in many cosmetic laboratories. The influx of computers has given the analytical chemist greater flexibility in data acquisition and their evaluation and interpretation. Raw data can be stored and manipulated at will, yielding more extensive information per experimental run. Introduction of these instruments has also brought an increase in analytical sensitivity. Ten years ago, routine analysis or structure elucidation required milligram to gram quantities of sample. Today, nanogram to microgram quantities are needed to obtain the same information. There has been a visible impact on the more traditional analytical tools, such as ultraviolet, visible, and infrared spectroscopy. Data stations now interface with these spectrometers, supplying computer assisted interpretation of data. Libraries of spectra are available which can be interfaced with the instruments and recalled at will for comparison with freshly generated spectra. A transformation of cosmetic analytical chemistry is emerging in all areas of the industry, from basic research to quality control. The purpose of this review is to elaborate on the current trends in the use of advanced instrumentation and on the analysis of important cosmetic raw materials such as surfactants, cosmetic preservatives, fragrances, etc. 4O7

408 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS INSTRUMENTATION For cosmetic chemists, packed column gas chromatography remains one of the most useful and quantitatively reproducible techniques for the separation and identification of volatile components in complex mixtures. Automatic injectors which are controlled by microprocessors can be interfaced at the front end of the gas chromatograph, and computing integrators with data storage capabilities can be interfaced at the back end. Dedicated systems of this configuration provide rapid and reliable results for routine quality control. Recently, capillary column gas chromatography has greatly improved the resolution over that obtained from packed columns. This technology has had the greatest impact in the area of fragrance analysis. Unlike most analytical techniques which are developed in academia and utilized in industry, high pressure liquid chromatography found its origin and growth in industrial problem-solving. The majority of raw materials used in the cosmetic industry are non-volatile, and HPLC has proven to be of particular value in the analysis of these materials. The technique has the ability to separate mixtures of components, but instead of the moving phase being a gas, the moving phase is a liquid. Chromato- graphic separation occurs by interaction between sample molecules and the stationary phase residing in a metal column. These interactions are essentially absent in the moving phase of GC, but they are present in the liquid phase of HPLC, thus providing an additional variable for controlling and improving separation. Also, chromatographic separation is generally enhanced as the temperature is lowered because intermolecular interaction becomes more effective. A greater variety of fundamentally different stationary phases allows separation using a number of hydrophobic and hydrophilic solvents. Another advantage of high pressure liquid chromatography is the relative ease of sample recovery. Separated fractions are collected in open vessels. Recovery is quantitative, and the isolated fraction can then be analyzed by ancillary techniques such as infrared or mass spectroscopy. An array of direct detecting techniques such as visible and ultra violet absorption, refractive index, electrochemical, and fluorescent detection allows for greater specificity in sample analysis. Recent advances in column technology in which the column packing is radially compressed has increased both efficiency and resolution of HPLC separation. An excellent treatise on HPLC can be found in Introduction to &lodern Liquid Chromatography by Snyder and Kirkland (1). Nuclear magnetic resonance spectroscopy has been useful in the analysis of cosmetic raw materials, especially in the area of surfactants. The spectrum can show many absorption peaks whose relative positions can yield detailed information about the molecular structure. The number of signals gives information on the number of different kinds of protons in the molecule. The position of the signal gives information about the electronic environment of each kind of proton. The intensity of the signal tells how many protons of each kind there are and the splitting of the signal into several peaks can tell us about the environment of a proton with respect to other, nearby protons. NMR has therefore found utility in structure elucidation and fingerprinting of organic compounds. Considering its ultimate and absolute potential, it is not surprising that the mass spectrometer is rapidly becoming the most universal detector. The need for quality analysis in response to competitive and regulatory pressure has been a motivating force in bringing this technique into the cosmetic industry. The introduction of quadrapole mass spectrometers, which have a lower price tag than the more conventional magnetic