ANALYSIS OF NITROSAMINES 315 • 1 oo ppb . • Jj ••._ 40 ppb i • 12 16 20 TIME (m•nules) Figure 22. HPLC-UV chromatograms of derivatized N-nitrosomethyldodecylamine standards on PRP-1 with 16.5:83.5 (v/v) acetonitrile-water with 0.008 M tetrabutylammonium hydroxide. Flow rate: 1.5 ml/min. Detection: 490 nm at 0.001 AUFS. Concentration of standards: O, 20, 40, 60, 80, and 100 ppb (nitrosamine derivative peaks arrowed).

316 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ! ! ! ! 4 I• 12 16 TIME (minutes) Figure 23. HPLC-UV chromatogram of derivatized nitrosamines in a model cosmetic matrix on PRP-1 with 16.5:83.5 (v/v) acetonitrile-water with 0.008 M tetrabutylammonium hydroxide. Flow rate: 1.5 ml/min. Detection: 490 nm at 0.001 AUFS (nitrosamine derivative peak afrowed). Under a contract from the Cosmetic, Toiletry, and Fragrance Association, Derse and Schroeder (34) have developed a colorimetric procedure for the determination of total nitrosamines in various model cosmetic matrices. This procedure utilizes the Griess reaction, followed by HPLC separation and quantitation of the dye species. The con- centration of the dye is directly proportional to the nitrosamine content of the sample (Figures 22 and 23). Note the full-scale absorbance of 0.001 AUFS, which requires very stable UV detectors with high signal-to-noise ratios to do the analysis at the ppb level. As mentioned earlier, a thorough study of matrix interferences is required when using colorimetric procedures for nitrosamine analyses. To date, several commonly used raw materials, including cellulose and cellulose derivatives, reducing sugars, methylisothia- zolinone, methylchloroisothiazolinone, castor oil, and other natural oils, have been shown to interfere in this system (34). SUMMARY Selected experimental data for the analysis of cosmetic, toiletry, and raw material ma- trices are shown in Tables XIV-XIX. The thermal energy analyzer is considered the