286 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS CH2OH CHOH HO OH -3- N203 --- CH2OH CHOH ø T + 2NO + H20 (lO) Table II Inhibition of Nitrosamine Formation Matrix Nitrosamine inhibitor Reference Foodstuffs Sausage, canned meat products, Vitamin E, thiamin, riboflavin, 295, 296, 300, nitrite-cured products nicotinamide, ascorbic acid, extract 301 of black tea leaves Industrial chemicals Dinitroanilines, herbicides, amine oxides, lubricants, antifreeze, hydraulic oil Sulfonyl halides, hydrogen peroxide, ascorbic acid, carbon dioxide 297, 298, 299, 302, 303 Other matrices Pharmaceuticals, cosmetics Primary & secondary amines, aromatic 302, 304 sulfonic acids Nitrosamines are relatively stable compounds and therefore difficult to destroy once formed. They are stable in neutral and strongly basic media in the absence of light. When exposed to ultraviolet light, they decompose to form either aldehydes, nitrogen, and nitrous oxide, or amine and nitrous acid (eq 11). The nature of the decomposition products is dependent on the wavelength of ultraviolet light used. In acidic media, decomposition via denitrosation occurs slowly. However, in the presence of nucleo- philes (e.g. iodide, thiocyanate, bromide, or chloride), denitrosation becomes rapid. A commonly used reagent for decomposing nitrosamines is hydrobromic acid in glacial acetic acid. Nitrosamines can also be reduced to the corresponding hydrazines by a variety of reducing agents (eq 12).

ANALYSIS OF NITROSAMINES 287 ! RCH2NNO hl• •' RCH + R'CH + N2 o o ! I LiA 1H 4 RCH2• RCH2NNO & R' / NNH2 (11) (12) ANALYTICAL METHODS AND APPLICATIONS The remainder of this paper will present an overview of the technology available for the analysis of nitrosamines in cosmetic matrices. For analytical purposes, nitrosamines are generally divided into two major groups: vola- tile nitrosamines (such as N-nitrosodimethylamine, N-nitrosodiethylamine, and N-ni- trosodipropylamine) and nonvolatile nitrosamines (including polar and low polarity ni- trosamines, such as N-nitrosodiethanolamine and N-nitrosomethylstearylamine). Non- volatile nitrosamines have occurred more frequently in cosmetics and cosmetic raw materials. The specific types of nitrosamines that may be formed are dependent on the types of precursors present. Many cosmetic products are formulated using a variety of nitrogen-containing compounds, many of which contain small amounts of amines as by-products or impurities. Hence, the corresponding N-nitroso compounds can poten- tially be formed through a variety of nitrosation reactions. The most commonly used amines in cosmetic products include di- and triethanolamine, both of which can yield the most frequently detected nitrosamine, N-nitrosodiethanolamine (NDELA). Table III describes some common cosmetic ingredients and their corresponding nitrosa- mine(s). SAMPLE PREPARATION The determination of trace contaminants such as nitrosamines requires the isolation and subsequent concentration of the analyte from the sample matrix in order to achieve the lowest possible detection limit for the particular technique. Sample cleanup is also required for removing potential matrix interferences. The importance of monitoring all possible sources of errors when handling analytes at these extremely low levels cannot be overemphasized (12-15). Thus, the development of trace analytical sample preparation procedures requires the use of a minimum number of processing steps, blank sample analysis to monitor matrix interferences, and recovery studies. Sample preparation procedures for cosmetic and cosmetic raw material matrices have been developed predominantly for the nonvolatile nitrosamine species such as N-nitro- sodiethanolamine. These isolation and concentration procedures are common to any subsequent analytical methodologies. Several common approaches have been utilized in the sample preparation of both fin- ished product and raw material matrices. Finished product matrices are complex mix- tures containing numerous raw material types. Each ingredient contributes as a diluent for the trace amount of nitrosamines that may be present. In addition, each constituent may also act as a potential interferent (e.g., when chromatographed, these constituents