Monitoring N-Nitrosamines in Cosmetic Thermal Waters: Analytical Method Development, Validation, and Market Analysis in Brazil

The cosmetics industry is expanding, with growing demand for natural and green products, including “cosmetic thermal water”. Brazil, the fourth largest cosmetic market of the world, has seen increased availability of these products, which may contain ingredients such as natural extracts, moisturizers, and preservatives, which can be potential sources of contamination with carcinogenic N-nitrosamines. This study aimed to map cosmetic thermal waters in Brazil, assess their composition and risk of N-nitrosamines formation, and develop and validate an analytical method for detecting N-nitrosamines in these products. A bidimensional liquid chromatography coupled with tandem mass spectrometry method was developed and validated for the precise quantification of N-nitrosodiethanolamine, N-nitrosodimethylamine, N-nitrosomorpholine, and N-nitrosodiethylamine in cosmetic thermal waters. The method was effective for most of the commercial samples analyzed. For accurate detection in the case of samples with more complex matrices, an offline solid phase extraction preparation method was also developed, ensuring reliable quantification for a variety of formulations. No detectable levels of the four N-nitrosamines were found in the 12 samples evaluated. The findings demonstrated the effectiveness of the method for monitoring contamination with N-nitrosamines in cosmetic thermal waters and indicated the need for ongoing surveillance and detailed analysis of formulations to ensure product safety.