Salt-assisted liquid-liquid microextraction-programmed temperature vaporizer-gas chromatography-tandem Q-Exactive Orbitrap mass spectrometry for simultaneous analysis of sixteen nitrosamines in drinking water

The prevalence of carcinogenic N-nitrosamines formed as byproducts during water treatment was public health of significant concern. The salt-assisted liquid-liquid microextraction (SALLME) combined with gas chromatography-tandem Q-Exactive Orbitrap mass spectrometry, employing programmed temperature vaporization–large volume injection (PTV-LVI) was developed for the determination of sixteen N-nitrosamines. The Plackett-Burman Design and Response Surface Methodology were applied to optimize the PTV-LVI parameters and sample pretreatment procedures. The optimal SALLME conditions were 200 μL dichloromethane as extraction solvent, 30 % (w/v) sodium carbonate concentration, and 40 s extraction time. The optimized PTV-LVI injection volume of 5 μL demonstrated approximately one order of magnitude greater sensitivity compared to conventional 1 μL splitless injection. Under these optimized conditions, the proposed method exhibited linearity correlation coefficients between 0.9947 and 0.9998 for sixteen N-nitrosamines within the range of 0.2–100 μg/L, except for NDMA and NMEA, which showed corresponding correlation coefficients of 0.9937–0.9941 over a linear range of 0.5–100 μg/L. The method detection limits ranged from 1.6 to 4.6 ng/L. The relative recoveries for spiked tap water samples at concentrations of 20 ng/L, 50 ng/L and 100 ng/L ranged from 60.4 % to 113.4 %, with the relative standard deviation below 10 %. The proposed method offered a rapid, environmentally friendly and highly sensitive alternative analytical method for the determination of trace level of N-nitrosamines in drinking water.