AWWA WQTC59000

AWWA WQTC59000 Detection of N-Nitrosamines in Water Using Solid Phase Extraction Combined with GC/MSD Ammonia Positive Chemical Ionization
Conference Proceeding by American Water Works Association, 11/02/2003

Charrois, Jeffrey W.A.; Arend, Markus W.; Froese, Kenneth L.; Hrudey, Steve E.

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Detection of N-nitrosodimethylamine (NDMA) and other nitrosamines in water supplies is ofconcern because many nitrosamines are classified as probable human carcinogens. A number of analyticalmethods exist for detecting nitrosamines in water but they are supported by GC/MS electron ionization(EI) methods, which are not selective and can produce potentially non-distinctive fragmentation patterns.Positive chemical ionization (PCI) using ammonia reagent gas is selective for amine and nitrosaminegroups, which provides increased selectivity compared to EI. Development of a selective, sensitive andaffordable bench-top analytical method for nitrosamines, at relevant drinking water concentrations (lowng/L range) was the primary objective of this project. In order to evaluate our method, N-nitrosamine-freewater was spiked with a mixture of eight N-nitrosamines as well as isotopically labeled standards.Samples were passed through a combination of solid phase extraction materials (Ambersorb 572 andLiChrolutEN). The analytes of interest were eluted with dichloromethane and concentrated under astream of nitrogen. Concentrated extracts were injected into an Agilent GC (6890) coupled with an MSD(5973) (single quadrupole) system operating in PCI-NH3 mode. Nitrosamines were detected usingselected-ion-monitoring and quantified using an isotope dilution method. Using this approach, the methoddetection limit for NDMA was 1 ng/L (S/N). To further validate this method, real drinking water sampleswere collected from three different water treatment plants and/or distribution systems, extracted andanalyzed for nitrosamines. The highest concentration of NDMA detected was from a distribution systemsample (180 +/- 10 ng/L). Several sample concentrations were independently confirmed by anotherlaboratory using GC/HRMS, with good agreement between the two sets of results. This method could be used as an important tool for investigating low molecular weight, polar compounds in water. Includes 13 references, tables, figures, appendix.