No abstract

Detection of N-nitrosamines in water supplies is an environmental and public health issue because many N-nitrosamines are classified as probable human carcinogens. Some analytical methods are inadequate for detecting N-nitrosodimethylamine (NDMA) at low ng/L concentrations in water due to poor extraction efficiencies and nonselective and nondistinctive GC/MS electron ionization techniques. Development of a selective, sensitive, and affordable benchtop analytical method for eight N-nitrosamines, at relevant drinking water concentrations was the primary objective of this project. A solid-phase extraction method using Ambersorb 572 and LiChrolut EN was developed in conjunction with GC/MS ammonia positive chemical ionization (PCI). Ammonia PCI shows excellent sensitivity and selectivity for N-nitrosamines, which were quantified using both isotope dilution/surrogate standard and internal standard procedures. Method detection limits for all investigated N-nitrosamines ranged from 0.4 to 1.6 ng/L. Applying our extraction method to authentic drinking water samples with dissolved organic carbon concentrations of 9 mg/L, we were able to detect N-nitrosodimethylamine (2-180 ng/L) as well as N-nitrosopyrrolidine (2-4 ng/L) and N-nitrosomorpholine (1 ng/L), two N-nitrosamines that have not been reported in drinking water to date. With high recoveries of standards and analytes, the described internal standard method offers a valuable new approach for investigating several N-nitroso compounds at ultratrace levels in drinking water.

A challenging aspect of structural elucidation of carbohydrates is gaining unambiguous information for anomers, linkage, and position isomers. Such isomers with identical mass can't be easily distinguished in mass spectrometry and a separation step is required prior to mass spectrometry identification. In our laboratory, gas-phase separation and differentiation of anomers, linkage, and position isomers of disaccharides was achieved using High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS). The FAIMS method responds to changes in ion mobility at high field rather than absolute values of ion mobility, and was shown to provide efficient separation and identification of disaccharide isomers at high sensitivity. Separation of analyzed disaccharide isomers can be accomplished at low nM level in a matter of seconds without sample purification or fractionation. Capability for examining a large population of ionic species of disaccharides by this method allowed for correlating structural details of disaccharide isomers with their separation properties in FAIMS. Results for disaccharide isomers indicate that this method could be applied to a larger group of carbohydrates. ( Mass spectrometry has shown a unique ability to resolve certain structural ambiguities. Permethylation is a well developed but time-consuming GC-MS method in linkage analysis of oligosaccharides [1,2]. Other methods implementing the derivatization of saccharides have been used to obtain their structural information [3][4][5][6][7][8][9][10][11]. The soft mass spectrometry ionization techniques such as fast atom bombardment (FAB) [12][13][14][15][16], liquid secondary ionization mass spectrometry (LSIMS) [17,18], along with matrix-assisted laser desorption ionization (MALDI) [19 -23], and electrospray ionization (ESI) [24 -28] have gained attention as approaches to investigate underivatized oligosaccharides. Collision-induced dissociation (CID) offers the possibility to assign details of carbohydrate structure such as sugar sequence for linear oligosaccharides [12], linkage position [12,[15][16][17]29], and differentiation of anomers [25,30]. In addition to analyzing protonated or deprotonated molecular ions of saccharides in CID, alkali metal adduct ions have been used to promote fragmentation of ligand-carbohydrate complexes. In the positive ion mode, calcium and magnesium adducts of oligosaccharides were investigated for the elucidation of the linkage position of trisaccharides [26] and cobalt complexes have been used to differentiate the anomeric configuration of disaccharides [30]. In the negative ion mode, decomposition of chloride adducts was investigated for differentiation of the linkage position of disaccharides [31].Despite recent advances in tandem mass spectrometry of carbohydrates, the spectral differences for some isomers are very small and they do not provide unambiguous identification. This is especially true when a mixture of isomers with the same m/z has to be analyzed. In such applications a separation step is required ...

Since the 1974 discovery of trihalomethanes as disinfection by-products (DBPs) in drinking water, the regulatory and public health focus has been primarily directed at halogenated compounds, even though it is well established that chlorination and chloramination also produce non-halogenated DBPs. Specific halogenated DBPs that could reasonably explain the correlation of some adverse health outcomes with consumption of disinfected drinking water in a number of epidemiologic studies have yet to be identified. We therefore explored an emerging class of non-halogenated DBPs, N-nitrosamines, which warrant consideration given public health concerns regarding possible correlations of bladder cancer with exposure to chlorinated drinking water. We developed a dual media (Ambersorb® 572 and LiChrolut® EN), off-line, solid-phase extraction method that utilized a modified commercially-available extraction manifold combined with our previous GC–MS ammonia positive chemical ionization (PCI) quantitative method for analyzing N-nitrosamines in drinking water. We surveyed 20 Alberta municipal drinking-water distribution systems for the presence of N-nitrosodimethylamine (NDMA) and seven other N-nitrosamine species. Analytical results revealed the occurrence of NDMA (up to 100 ng/L) as well as two other N-nitrosamines (N-nitrosopyrrolidine and N-nitrosomorpholine) within select Alberta drinking water supplies.Key words: Alberta, chloramination, disinfection by-products, distribution system, drinking water, N-nitrosamines, NDMA, public health, survey.