Analysis of Brominated Compounds in the Atmosphere by the Photodetachment-Modulated Electron Capture Detector

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In recent years it has become increasingly recognized that brominated compounds (BrC's) in the atmosphere may play a significant role in stratospheric ozone depletion, especially in the Antarctic and Arctic regions. Most of the attention, to date, concerning stratospheric ozone depletion has centered on the role of chlorinated compounds (ClC's), due in part to their relatively high concentrations in the troposphere, now totaling well over a part per billion (mole ratio). One of the greatest challenges associated with atmospheric studies of the BrC's is related to their relatively low concentrations in the troposphere, typically in the low or sub parts per trillion range. The BrC's are therefore relatively difficult to detect and quantitatively analyze in atmospheric samples that invariably contain a large excess of other organic compounds, including the ClC's. In this research, a new instrument, will be applied to the analysis of BrC's in atmospheric samples. This instrument is called the SiF4-doped Photodetachment-Modulated Electron Capture Detector (SiF4-PDMECD) and has been shown to provide sensitive responses to BrC's, but does not respond to ClC's or other organic compounds. In this project, the SiF4-PDMECD will be evaluated specifically for the analysis of BrC's in the atmosphere and will thereby provide the field of atmospheric chemistry with an additional and very possibly a superior analysis capability for future investigations of the atmospheric chemistry of brominated compounds.