Real-time Measurements in Real-world Samples: Fate and Distribution of Trace Organic Contaminants by Direct Mass Spectrometry

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This research program centres on the development and application of innovative real-time mass spectrometry (MS) techniques for the direct and continuous measurement of molecular determinants of environmental and human health. Direct MS is an extremely powerful analytical platform that enables high throughput, time-resolved, and in-situ measurements. These unique capabilities address several long-standing constraints to current understanding of the fate and distribution of contaminants of emerging concern by providing molecular level information in complex samples with applications in real-time monitoring and advanced spatiotemporal analysis. This research will 1) develop novel direct sampling methods for new contaminant classes, 2) study environmental chemical processes in complex media, and 3) mobilize MS for in-field measurements in air, water, and sediments. These goals are realized by developing sensitive and selective MS methods that are fast, simple, and robust. In the absence of chromatographic separation, direct MS relies on selectivity imparted by the sample introduction method, ionization mechanism, and the mass spectrometer. In membrane introduction methods, molecules permeate into an acceptor which is continuously infused into a mass spectrometer. Understanding factors that control mass transport allow us to improve selectivity and design novel membrane-based strategies using new materials, electrical gradients, and chemical modifiers. Field asymmetric waveform ion mobility spectrometry represents an ideal pairing with direct MS applications as it provides fast, orthogonal separation (based on differential mobility). It is readily paired with high resolution, lab-based instruments and lower cost, portable MS, providing the opportunity to develop methods for subsequent in-field applications. Time-resolved MS techniques provide unique insight into the mechanisms of chemical and physical processes that affect the transformation of contaminants in the environment. Membrane introduction MS techniques are employed to follow changes in the concentration of analytes in heterogeneous samples including sorption of trace contaminants on microplastics and photochemical degradation of naphthenic acids in oil sands process waters. Proton-transfer reaction MS provides continuous on-road measurements of volatile organic compounds that yields chemical concentrations mapped at the neighborhood scale and compositional information to `finger-print' sources and apportion contributions. The research described here opens important new territory in environmental chemical analysis by developing next-generation methods to provide real-time molecular level information in real-world samples. Providing chemical information `when' and `where' it is needed enables environmental assessment and forensics at unprecedented spatiotemporal resolution. As such, this research contributes directly to environmental protection and healthy communities.