Rapid method for monitoring N-nitrosodimethylamine in drinking water at the ng/L level without pre-concentration using high-performance liquid chromatography-chemiluminescence detection

• A method for the ultra-sensitive determination of NDMA was developed.
• The method detection limit for NDMA by the proposed HPLC system was 0.2 ng/L.
• A simple sample preparation procedure was developed for drinking water analysis.
• A long-term monitoring of NDMA were performed.

As a contaminant in drinking water, N-nitrosodimethylamine (NDMA) is of great concern because of its carcinogenicity; it has been limited to levels of ng/L by regulatory bodies worldwide. Consequently, a rapid and sensitive method for monitoring NDMA in drinking water is urgently required. In this study, we report an improvement of our previously proposed HPLC-based system for NDMA determination. The approach consists of the HPLC separation of NDMA, followed by NDMA photolysis to form peroxynitrite and detection with a luminol chemiluminescence reaction. The detection limit for the improved HPLC method was 0.2 ng/L, which is 10 times more sensitive than our previously reported system. For tap water measurements, only the addition of an ascorbic acid solution to eliminate residual chlorine and passage through an Oasis MAX solid-phase extraction cartridge are needed. The proposed NDMA determination method requires a sample volume of less than 2 mL and a complete analysis time of less than 15 min per sample. The method was utilized for the long-term monitoring of NDMA in tap water. The NDMA level measured in the municipal water survey was 4.9 ng/L, and a seasonal change of the NDMA concentration in tap water was confirmed. The proposed method should constitute a useful NDMA monitoring method for protecting drinking water quality.