A new method for quantifying N-nitrosamines in wastewater samples by gas chromatography—triple quadrupole mass spectrometry

We developed a methodology for the separation, identification, and quantification of eight N-nitrosamines. For a range of wastewater samples, including raw sewage and final-discharge wastewater, the methodology, which was based on solid-phase extraction (SPE) and a purification technique followed by analysis using a gas chromatograph equipped with a triple-quadrupole mass spectrometer, gave effective separation of the targeted compounds. The limits of detection of this method for N-nitrosamines in wastewaters ranged from 0.1 to 1.0 ng L−1 and the limits of quantification ranged from 0.4 to 3.3 ng L−1. As a result of preliminary recovery testing, we decided on a combination of two types of sorbent cartridges for SPE—one was aminoprophyl for sample purification and the other was activated charcoal for analyte concentration—that gave excellent recovery rates (98% to 152%) of three deuterided nitrosamines (surrogates). Using this combination of SPE, internal surrogates, and an injection surrogate, we obtained good recovery rates (80% to 131%) with low relative standard deviations (1% to 14%, n=3) for eight N-nitrosamines in all samples of influent, secondary effluent, and final discharge. We applied the newly developed pre-treatment method to an influent wastewater samples. All of the N-nitrosamines except two (NMEA and NDPA) were detected in the influent sample, at 1 to 1057 ng L−1.