Nitrosamines determination in drinking water using a new GC-­MS/MS method coupled with automated solid phase extraction

Abstract

A new sensitive, selective and accurate GC-MS/MS method with positive electron impact ionization coupled with an automated SPE extraction was developed to detect seven nitrosamines (NDMA, NDEA, NMEA, NPIP, NPYR, NDPA, and NDBA) from several drinking water sources in Romania. The method separated all seven nitrosamines using a Zebron Inferno ZB5HT column (60 m x 0.25 mm i.d. x 0.25 μm df) and He (6.0 purity) as carrier gas at 1.0 mL/min. A fast temperature gradient (15°C/min from 40 to 280°C) allowed efficient separation of the nitrosamines in 23 minutes. Optimization of all GC and MS parameters: injector, oven temperature program, collision energy, ionization source temperature, SRM transitions and others, generated low instrumental LOQ values ranging between 0.95 and 4.50 μg/L. Two MS/MS transitions were used, one for quantification (quantifier) and one for identification (qualifier) of the target compounds. Calibration curves were linear in the range 0.5 – 100 μg/L with R2 > 0.999 for all nitrosamines. Automated SPE using activated charcoal cartridges (2g, 6 mL) and dichloromethane (8 mL) were used to extract and concentrate nitrosamines from drinking water by a factor of 500. Overall method LOQs were situated in the range 2.3 – 11.2 ng/L. The SPE-GC-MS/MS method was fully validated with respect to specificity, linearity, precision, recovery, accuracy and LOQ, and provided good results. The obtained intraday and interday precision values (RSD%) were situated between 4.8 – 6.8% and 6.6 – 10.8%, respectively. Method accuracy was good with absolute recovery values between 77.5 and 93.6%. The developed SPEGCMS/ MS method was tested on several raw and treated water sources from Romania and found mainly NDMA, NDEA at concentrations ranging between 2.8 and 13.5 ng/L. These values are in accordance with previous studies performed in Europe and worldwide.