INSTRUMENTATION IN THE COSMETIC I,ABORATORY 327 of hexachlorophene. The total time required to analyze three samples in this manner is approximately thirty minutes whereas if this analysis were attempted by chemical means, separation and isolation steps would be required and the time requirement would be at best, several hours. In Fig. 4 is shown the differential ultraviolet spectrum of pure hexachloro- phene, a normal spectrum of a sample containing hexachlorophene with interfering adsorptions and the differential spectrum of this same sample. Another tool which can replace many tedious chemica! analyses is in- frared spectrophotometry. A qualitative spectrum compared to a stand- ard sample, and in some cases complemented by quantitative determina- tions, form a portion of the basis for acceptance or rejection of a shipment. / bJ oo :Do •[n,- 0 _1_o ._In,' I•. n" ..• 0o O- o I-'0 Z m Z © INFRARED ABSORPTIONS REDISTILLED PEPPERMINT OIL NaCL PRISM WAVELENGTH IN MICRONS Figure 5. One example of infrared spectrophotometry replacing tedious chemical analyses is the monitoring of peppermint oil purchases. A complete spectrum of peppermint oil is run and compared to previous shipments to observe if any gross differences are evidenced. Then the four major components of peppermint oil (menthol, menthyl acetate, menrhone and mentholutah) are quantitatively determined by infrared. In Fig. 5 is shown a gross spectrum of peppermint oil and the spectral regions that are utilized in the analysis of the major components of the oil. Quantitative measurements are made using the "base line" method. The quantitative absorption peak used for the determination of menrhone

328 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS is 5.8 microns for menthyl acetate, 8.05 microns for menthol, 10.9 microns and menthofuran is determined at 13.6 microns. Alkanolamides which are fatty acid amides derived from monoethanol- amine, diethanolamine or monoisopropanolamine are used to enhance foaming characteristics or as emulsification agents. It is frequently necessary to distinguish among these types in product isolates or in the product itself. Figure 6 which shows the infrared spectra of these three amides demonstrates that this technique is ideally suited for this work. It is observed that all three compounds exhibit hydroxyl absorption in the 2.9-3.1 micron region, amide and methylene chain absorption at 6.1-6.2 and 13.9 microns, respectively, and INFRARED SPECTRA OF ALKANOLAMIDES L-M DIETHANOLAMIOE L-M ISOPROPANOLAMIDE COCO MONOETHANOLAMIDE WAVELENGTH IN MICRONS Figure 6. a trace of ester at 5.7-5.8 mi- crons. The monoethanolamide and the diethanolamide have ab- sorption peaks in the 9.2-9.6 mi- cron region which is characteristic of primary alcohols whereas the isopropanolamide shows secondary alcohol absorption at 8.7-9.0 microns. Therefore, at this point, the primary alcohol amides can be differentiated from secondary alcohol amides. The mono- and diethanolamide can be distin- guished from one another at 6.4 and 3.25 microns which are char- acteristic of the carbonyl and N-H vibration regions, respectively. The application of the infrared technique as a means of identification of isolated components in cosmetic products is invaluable. There are occasions where it is necessary to control or distinguish the type of gum that is being used in a product. The spcctra in Fig. 7 demonstrate the specificity of infrared spectrometry. Here are seen the spectra of three widely used gums carboxymethylcellulose, Veegum and Irish moss. Examination of these three spectra will show that if one of these gums is isolated from a product, its identification can easily be made bv merely comparing its infrared spectrum to the three standard curves. Irish moss exhibits characteristic peaks at 8.08, 10.77 and 11.85 microns which distinguish it from the other two gums. Veegum is an inorganic substance which is composed primarily of SiO2. The infrared spectrum of Veegum exhibits a broad absorption band at 9.25 to 10.25 microns which is characteristic of SiO2. Veegum, being inorganic, shows no absorption in the 3.3-3.5 micron region which would denote the presence of CH2 and