Multiplexed Ion-Mobility Time-of-Flight Mass Spectrometry for the Study of Iron Biogeochemical Cycling in Seawater

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With support from the Biocomplexity in the Environment - Instrument Development for Environmental Activities (BE-IDEA) Program, Richard Zare in the Chemistry Department at Stanford University will develop instrumentation based on ion-mobility spectrometry - time-of-flight mass spectrometer (IMS-TOF-MS) to investigate poorly understood aspects of the iron biogeochemical cycle: (a) the role of iron in the photochemical reactivity of surface water Chromophoric Dissolved Organic Matter (CDOM); (b) the influence of iron complexation by tetrapyrroles in its role as a micronutrient in marine systems; and (c) study of the biochemical fate of iron associated with heme and iron-sulfur moieties in metallo-proteins. Two different Ion-Mobility (IM) drift tubes will be designed and built to be coupled to existing mass spectrometers: one employing Hadamard multiplexing at the Time of Flight (TOF) analyzer and another that uses Hadamard multiplexing at the IM drift tube. The goal is to improve sensitivity allowing for the analysis of very dilute seawater samples while simultaneously providing two- and three-dimensional information to identify unknown iron-binding chemical species. This project involves researchers at three institutions: Scripps Institute of Oceanography, Georgia Institute of Technology and Stanford University. These instruments will boost novel features allowing high sensitivity and high mass accuracy. The ion mobility spectrometry capability will provide conformation and isomeric information about iron-macromolecular complexes. Graduate and undergraduate students directly involved in the building stages of the project will be trained in instrument development and environmental activities. Results will also be valuable for companies seeking to develop mass spectrometry instrumentation focused on environmental analysis.