Re-assessing the Formation of N-nitrosamines during Chloramination of Various Nitrogenous Compounds using Specific and Total N-nitrosamines Analysis

N-nitrosamines (NOAs) are potent carcinogenic and mutagenic compounds that can be present in water, biological fluids, food, consumer products and cigarette smoke. Several studies have shown that the formation of NOAs in water can arise from the reactions of amine precursors with chemical oxidants such as chloramines, chlorine or ozone.1–3 So far most of the studies published on NOAs in water have focused on only nine specific NOAs selected by the US-Environmental Protection Agency (EPA). However several recent studies have shown that the NOAs selected by the US-EPA might account only for ~5-15% of the total NOAs concentration (TONO) in wastewater.2,4 Therefore, quantifying the TONO is necessary to assess the overall risk associated with the presence of NOAs in water. Many tertiary and quaternary amines present in consumer products (e.g., pharmaceuticals, personal care and household products) are known to be N nitrosodimethylamine (NDMA) precursors during chloramination, but the formation of other NOAs has been rarely studied.5 In this study we have re-evaluated the NOAs formation potential (FP) of various nitrogen-containing micropollutants (chlorhexidine, metformin, benzalkonium chloride and cetyltrimethylammonium chloride) and tertiary and quaternary model amines (trimethyl amine, N,N dimethylbutyl amine, N,N dimethylbenzyl amine and tetramethyl ammonium) using specific NOAs and TONO analysis. All the studied nitrogenous micropollutants displayed quantifiable TONO FP, with molar yields ranging from 0.04 to 11.92%. However, the observed TONO pools constituted mostly of uncharacterized species, not included in US-EPA 8270 NOAs standard mix. Only the benzalkonium chloride showed quantifiable NDMA FP (0.56% molar yield), however, explaining only a minor fraction of the observed TONO FP. The studied model amines showed molar NDMA yields from 0.10% to 5.05%, very similar to the molar TONO yields. LC-qTOF screening of a list of proposed NOAs structures has enabled to identify a novel NOA (N-nitroso-N-methyldodecylamine) from the chloramination of benzalkonium chloride. This finding supports the hypothesis that different functional groups in quaternary amines can act as leaving groups during chloramination and form differing NOA structures at significant yield.