Characterization of nitrosation products in cosmetics raw material samples has been accomplished by three liquid chromatography/mass spectrometry (LC/MS) techniques. Two of the techniques involved conventional methodologies of LC/MS and LCltandem mass spectrometry, both of which can be used to detect and identify products formed under extreme-nitrosation conditions. The third technique utilized an on-lime coupling of a photolysis reactor with the LC/MS, and it may be used as a rapid and specilk means of screening for the presence of known and unknown N-nitrosamines, which may be carcinogenic.
The detection and identification of N-nitrosamines in cosmetics and their raw materials is important because of the relatively small amount of information available regarding identity and concentration of a large number of N-nitrosamines in these products.' Researchers have estimated that the known N-nitrosamines (e.g., N-nitrosodimethylamine, N-nitrosopiperdine, etc.) account for only 10% of the apparent total N-nitrosamines.'
Previous studies on N-nitrosamine determination have utilized conventional analytical methods such as gas chromatography (GC) or liquid chromatography (LC) coupled with a thermal energy analyzer (TEA)." The disadvantage of such techniques, however, has been that subsequent mass spectral confirmation is needed to minimize false-positive response.5r6 Techniques such as GUMS and, in some cases, LC/MS offer a means for separating, detecting and confirming N-nitrosamine presence.
Determination by GUMS has been restricted to lowmolecular-weight (i.e., volatile and semi-volatile) N-nitrosamines, whereas investigations involving highmolecular-weight N-nitrosamines have not received much attention because of their low volatility. Derivatization procedures, however, make them sufficiently volatile for GC.7
Current LC/MS methods have become an attractive alternative to GUMS since they require no derivatization and can handle a wide volatility range of compounds. However, most LC/MS methods yield only the protonated molecualr ion. Collision-induced dissociation (CID) in the source region of the mass spectrometer has been utilized as a means of producing structurally significant ions for a wise variety of compounds.' For N-nitrosamines, however, CID has yielded relatively complicated fragmentation patterns.' CID of N-nitrosamines does not produce easily identifiable fragment ions, making it particuarly restrictive in a regulatory environment when trying to analyze a large number of samples where both known and unknown Nnitrosamines may be present.