Ultratrace analysis of nitrosodipropylamine in drinking water by Ice Concentration Linked with Extractive Stirrer gas-chromatography electron-ionization mass-spectrometry

Nitrosoamines (NAs), including nitrosodipropylamine (NDPA), are highly toxic drinking water contaminants with minimum reporting levels (MRLs) in the parts-per-trillion range (0.2-20 ng/L). The quantification of NAs at these concentrations is extremely difficult, requiring both sophisticated instrumentation and laborious sample preparation procedures. An advanced sample preparation technique, ICE Concentration Linked with Extractive Stirrer (ICECLES), coupled with gas-chromatography mass-spectrometry, was used to analyze NDPA (MRL = 7 ng/L). ICECLES allowed ultratrace analysis of NDPA, producing an LOD of 0.2 ng/L, will below the MRL, and a linear range of 2-50 ng/L (using NDPA-d14 as an internal standard). Both inter- and intraassay precisions were ≤13%RSD, while the method accuracy was 100 ± 17.5%. The ICECLES method was applied to screen for possible NA contamination in selected drinking water sources. The concentration of NDPA in one drinking water source was 2.38 ± 0.34 ng/L and was detected (i.e., concentrations ≥ LOD), but was not quantifiable, in the other samples.