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

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.