Picogram determination of N-nitrosodimethylamine in water

Abstract

N-nitrosodimethylamine (NDMA) persistence within surface waters is a major concern for downstream communities exploiting these waters as drinking water supplies. The objective of this study is to develop a novel and efficient analytical method for NDMA via different technologies: pulsed splitless gas chromatography–nitrogen phosphorus detector (GC–NPD), large volume injection (LVI) gas chromatography–mass spectrometry (GC/MS) via programmable temperature vaporizer (PTV) inlet or PTV-gas chromatography– triple quadruple mass spectrometry (GC-MS/MS) and continuous liquid–liquid extraction. It was found that the sensitivity required for NDMA analysis by GC–NPD can only be achieved when the NPD bead is extremely clean. LVI via PTV can greatly improve GC-MS system sensitivity for analyzing NDMA. With the help of DB-624 (25 m × 200 μm × 1.12 μm) connected with DB-5MS (30 m × 250 μm × 0.25 μm) in series, PTV–GC/MS could overcome the matrix interference for the trace analysis of NDMA. Variable instrument conditions were studied in detail, with the optimized process being validated via precision and accuracy studies. PTV- triple quadruple GC-MS/MS system could efficiently remove the interference on a single DB-5MS (30 m × 250 μm × 0.25 μm) column with good sensitivity and selectivity. The developed methods have been successfully applied to test NDMA in different types of water samples with satisfactory results.