With this award, the Chemical Measurement and Imaging Program in the Division of Chemistry is supporting Professor Kaveh Jorabchi at Georgetown University to develop high-sensitivity detection and quantification techniques for halogenated organic compounds. These compounds, known as organohalogens, have broad applications as pharmaceuticals, pesticides, and fire retardants, and are also found among food contaminants. They are typically present at low concentrations but have significant environmental and health impacts. Therefore, it is vital to develop highly sensitive analytical methods to detect and quantify these compounds. The proposed research, if successful, will substantially enhance the efficiency of organohalogen characterization methods for many biological and environmental applications. The supported research will also strengthen collboration between Professor Jorabchi's group and an industrial partner and facilitate rapid translation of academic research into applied technologies. This research project will provide graduate students with interdisciplinary training opportunities. Professor Jorabchi will continue his outreach activities to local high school students,with particular effort to reach members of underrepresented groups and promote the pursuit of studies in STEM fields. <br/><br/>Halogen atoms can serve as intrinsic tags for absolute quantification of organohalogens by elemental mass spectrometry. However, existing elemental mass spectrometric methods suffer from low halogen detection sensitivity, limiting these methods for trace analysis of organohalogens. Professor Jorabchi's research aims to significantly improve elemental detection sensitivity for fluorine, chlorine, and bromine by developing a plasma-assisted reaction chemical ionization (PARCI)approach centered around efficient generation of negative ions. Specifically, Professor Jarobchi will (i) characterize electron capture ionization of halogens in GC (gas chromatography)-PARCI-MS (mass spectrometry) with a sufatron cavity,(ii) characterize proton transfer reactions for halogen ionization in GC-PARCI-MS, and (iii) study electron capture and proton transfer ionization in atmospheric-pressure PARCI-MS for analysis of compounds eluting from the LC (liquid chromatography). The successful conduct of the proposed work will enable online and high-sensitivity detection of organohalogens separated by liquid and gas chromatography, and could provide quantitative information without compound-specific standards, a critical analytical capability for characterizing degradation and metabolic products of organohalogens in environmental and biological samples.