Sensitive determination of volatile nitrosamines with ambient pressure ammonium-adduct ionization mass spectrometry

In recent years, the control of volatile N-nitrosamines (NAs) has been of interest in the pharmaceutical and food industries, as many of these compounds are probable human carcinogens. Thus, rapid and trace-level quantitative determination methods are in urgent demand. In this work, ambient pressure ammonium-adduct ionization mass spectrometry was proposed for the sensitive detection of volatile nitrosamines in various pharmaceutical headspaces. The ammonium ions produced through electrospray ionization acted as reactant ions for NAs to generate ammonium-NA adduct ions and underwent in-source collision-induced dissociation to produce protonated NAs, which were detected by mass spectrometry. The ionization selectivity and sensitivity for various volatile NAs were improved significantly using the developed method, which was demonstrated by the limit of quantification (LOQ) below 52 ng L^-1 for all NAs, and the quantitative performance was consequently improved. Different NAs exhibited almost equimolar response using NH₄⁺ as the reactant ion, with at least a twofold enhancement in intensity for the individual compounds relative to when using H⁺ as the reactant ion. The proposed method is a rapid, sensitive, and environmentally economical approach that uses few reagents.