Because nitrosamines are recognized as highly potent potential carcinogens, their presence in drinking water needs to be closely monitored. This led to the development of USEPA Method 521, Determination of Nitrosamines in Drinking Water by Solid Phase Extraction and Capillary Column Gas Chromatography with large volume injection and Chemical Ionization Tandem Mass Spectrometry (MS/MS).

Positive ion chemical ionization (PCI) can be utilized as an ionization technique for mass spectrometry.  Different reagent gases have differing proton efficiencies, and this affects the resultant spectra and ions.  Reagent gases were evaluated that would more closely match the proton affinities of the ionization agent and nitrosamines. Since there is concern that the dispersion of the ion current into adducts and primary ions may lead to reduced sensitivity in MSn modes of operation, reagent gas selection focused on a gas that would create primarily the [M+1]+. This ion would then be isolated for the MS/MS experiment.

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