Colorimetric Detection of Aqueous N-Nitrosodimethylamine via Photonitrosation of a Naphtholsulfonate Indicator

Jessica C. Beard, Chi-Hsien Wang, Arun Sridharan, Robert G. Croy, John M. Essigmann, Timothy M. Swager

Link to Paper: https://doi.org/10.1021/acssensors.4c00927

N-Nitrosamines are contaminants found throughout the environment, including in drinking water, and many nitrosamines are likely potent carcinogens. Correspondingly, there is need for rapid and cost-effective in-field detection methods that can provide timely information about their contamination levels in water. This study details a colorimetric assay for detecting aqueous N-nitrosodimethylamine (NDMA) by photochemical nitrosation of a commercial naphtholsulfonate, to offer an attractive alternative to traditional laboratory-based analysis. The resulting naphthoqui-none-oxime coordinates to aqueous iron (II) ions to form a green complex, allowing for direct visual detection. Characterization via Mössbauer and electron paramagnetic resonance (EPR) spectroscopy, alongside single-crystal structure determination, provides comprehensive structure information of the iron indicator complex. Optimization of detection conditions, including UV irradiation and response times, led to an improved colorimetric detection method with a limit of detection of 0.66 ppm for NDMA. The practical applicability and selectivity of this colorimetric detection scheme make it a promising candidate for the development of field-deployable sensors for NDMA in environmental water samples.