About the Seminar:
Recent advancements in high-resolution mass spectrometry (HRMS) and its application to the field of environmental chemistry have for the first time made possible identification of emerging contaminants in complex environmental mixtures without a priori knowledge of contaminant identity or occurrence. Here, I present a strategy and series of novel analytical workflows based on liquid chromatography, high resolution tandem mass spectrometry (MS/MS), and new chemoinformatics tools (e.g. data processing, spectral library searching, and in silico MS/MS prediction) for identification of emerging environmental contaminants in ecological and indoor environmental samples. In this approach, high resolution (R>240,000) accurate mass (mass error < 1 ppm) analyses of environmental extracts are subjected to recursive peak assignment, adduct grouping, isotope pattern scoring, and molecular formula assignment. Molecular candidates are then subjected to confirmation criteria for tentative structural identification using rule-based in silico fragmentation, library searching, and comparisons to literature data.
I will discuss application of these methods to assess fate and occurrence of emerging contaminants in several environmental systems relevant to ecological and human exposure, including:
- Assessment of polar organic contaminant occurrence and fate in North Carolina drinking water sources. Our results revealed a complex mixture of natural and anthropogenic organic compounds in NC surface waters, with analytical signals detected for > 5,000 discrete compounds, and high-confidence tentative structural ID’s for > 300 of these. The tentatively identified compounds present at high relative intensity included markers of wastewater (e.g. sucralose, methylbenzotriazoles, and pharmaceuticals), stormwater (e.g. benzothiazole and substituted urea and guanidine vulcanization accelerants), and agrochemical input (e.g. simazine, atrazine, and fungicides such as carbendazim).
- Elucidation of chemical structures corresponding to novel halogenated azobenzene dyes in the indoor environment. We have tentatively identified > 30 disperse dyes in house dust, six of which were identified definitively in our extracts using authentic standards (representing 100% verification success for proposed tentative structures for these candidates). Prominent compounds identified in dust include the brominated dyes Disperse Blue 373, Disperse Violet 93, and Disperse Orange 61, along with several chlorinated analogs of these structures. Together, these compounds comprise the major components of one of the most commonly applied black dyes used for coloring synthetic fabrics. Quantitative measurements indicated that these dyes were present in house dust samples at levels up to 10 µg/g. Apart from their known mutagenicity, disperse azobenzene dyes are also implicated as contact allergens, thus their occurrence in the indoor environment is of concern with regard to human exposure potential.