N-nitrosamines are genotoxic impurities that have become the focus of the pharmaceutical industry in recent years. This doctoral thesis comprehensively addresses N-nitrosamine-related challenges in medicines, food supplements and cosmetics. The comprehensive analytical methodology for the simultaneous determination of multiple N-nitrosamines was developed, combining advanced sample preparation with liquid chromatography coupled to high resolution mass spectrometry. Four innovative state-of-the-art analytical approaches with high sensitivity, selectivity, robustness, and accuracy were established for the determination of the largest number of regulated low-molecular-weight N-nitrosamines reported to date in medicines and cosmetics, as well as emerging N-nitrosamine drug substance-related impurities (NDSRIs) in medicines and food supplements. Analytical methods were further applied to 215 different products (51 medicines, 53 cosmetics, 111 food supplements) on the Slovenian market. Our findings show that N-nitrosamines are present in these products, with limited occurrence in medicines complying with current regulatory requirements, whereas N-nitrosamines were detected in 30% of cosmetics, with 15% exceeding the regulatory limit by up to threefold. NDSRIs were detected in 43% of food supplements, with three products exceeding the regulatory limit applicable to medicines. Special attention was paid to investigating the factors contributing to N-nitrosamine occurrence in cosmetics and food supplements. Structural characteristics, the content of precursors and nitrites were identified as key factors in N nitrosamine formation during storage. Furthermore, the emerging N-ethyl-N-(2-hydroxyethyl) nitrosamine was identified in these products for the first time. In the final part of the thesis, a comprehensive assessment of daily N-nitrosamine exposure from multiple sources was performed for the first time, combining a systematic literature review with our own data on N-nitrosamine occurrence and considering their genotoxic potential. It was demonstrated that tobacco products are the predominant source of exposure (68%), followed by food (16%) and cosmetics (12%), whereas medicines, food supplements and drinking water made only a negligible contribution to total exposure.
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