INSTRUMENTATION IN THE COSMETIC LABORATORY 32.t (19) Nagel, W., and Mertens, W., Bet., 69, 2050 (1936). (20) Boeseken, J., and Meulenhoff, J., Proc. Acad. Sci. Amsterdam, 27, 174 (1924). (21) "Shellac," private publication, Angel() Bros., Cossipore (Calcutta). (22) Bhattacharya, R., and Gidvani, B. S., I,ondon Shellac Research Bureau, Technical Paper No. 15 (1938). INSTRUMENTATION IN THE COSMETIC LABORATORY By G. M. LEt(m and A. P. KENT* Presented May 12, 1961, New York City A•:rHOUGI-t the spatula continues to be a useful instrument, more astute apparatus has become an essential part of the modern cosmetic laboratory. The term instrumentation in this instance is applied generi- cally to the spectral and chromatographic facilities which in less than twenty years have become basic tools of the industry. Many did not even exist twenty years ago. Instrumentation as applied to analysis, control, elucidation of structure, product development and cosmetic research is an essential adjunct to the laboratory. The wide variety of raw materials and the complexity of formulations typical of the cosmetic industry today make rapid, precise and specific means of analysis mandatory. Spectral and chromatographic instrumenta- tion fulfills this requirement in increasing variety and utilization is now, in many instances, routine. After much early work in paper and columnar chromatography, gas-liquid partition chromatography finds a wide range of application from the assay of raw materials to the determination of extremely low concentrations of a specific ingredient in a finished formula- tion. In many cases samples need not be altered, or only a minute amount may be necessary for analysis. For repetitive work enormous savings of time may be achieved, and in research instruments lead the way to more revealing methods and frequently to basic discoveries. The following examples will demonstrate the scope and versatility of these instrumental techniques. Stearic acid or most fatty acids or their triglycerides can be rapidly and accurately assayed by means of gas chromatography. The methyl ester is prepared, perhaps by the boron trifluoride method, and injected into the instrument. From the resulting chromatogram, the type and con- centration of the impurities can be determined in addition to the assay of the acid. Figure l shows a typical chromatogram of a stearic acid * Colgate. Palmolive Co., Jersey City 2, N.J.

324 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS sample. Calculations based on peak areas indicate this commercial sam- pie to contain 86 per cent stearic acid and also to contain 13 per cent palmitic acid and I per cent oleic acid. Acid and saponification values would be more time consuming and still not give as complete information as can be obtained from one gas chromatogram. Acid or saponifica- tion values represent the average composition of the sample whereas a gas chromatographic analysis will give specific information 'as to the fatty acid distribution. STEARIC ACID TEMP 185 øC. 14 lbs. psio. HELIUM 90 CC/min ' COLUMN 5FT. 25 % dl - ETHYLENE GLYCOL SUCCINATE ON CHROMOSORB W PALMITIC ACID 1:5% Figure 1. STEARIC ACID 86% C ACID I% The gas chromatographic technique can also be utilized in the quality control of flavors and perfumes or for the quantitative determination of single component in a finished product. An example of this is the deter- mination of menthol in shaving cream preparations. The concentration of menthol in these products is less than 1 per cent but, as is indicated in Fig. 2, the peak obtained for menthol is more than adequate to insure satisfactory analytical precision. In this procedure, a calibration curve for menthol is prepared based on peak area and after suitable preparation of the sample, the peak area obtained from the chromatogram is readily translated to per cent menthol. Ultraviolet and visible spectrophotometry have found widespread applicability in the cosmetic industry. Visible spectrophotometry can be employed for the standardization of colors of the labels, package or the product itself. Once the spectrum of a color standard is obtained, it constitutes a permanent record and is available for comparison with future samples. Visual comparison of colors, no matter how discerning the eye, cannot compare with the spectrophotometric technique for accuracy and reproducibility. If the color of the standard sample happens to degenerate with time, the spectrum of the sample will still be a representation of its original state. Figure 3 demonstrates a typical application of this tech- niq ue.