Student Research: Eric Coker

, Occupational & Environmental Exposure Sciences (OEES), 2009
Faculty Advisor: Michael G. Yost

Measurement of Gasses by UV-DOAS for a Reference Spectral Library


Abstract

Air monitoring of gases by Ultraviolet Differential Optical Absorption Spectroscopy has been shown to provide excellent sensitivity and specificity over long measurement path lengths. This spectroscopic detection method requires an accurate reference library of molecule specific absorption spectra in order to conduct field measurements. The present study created reference absorbance spectra for eight important air pollutants over a range of relevant ambient concentrations. The following compounds were the focus of this study: NO, NO2, SO2, Ammonia, Formaldehyde, Benzene, 1,3-Butadiene, o-xylene, and Dichloromethane. References from this study were compared with reference spectra downloaded from an online databas, the MPI-Mainz-UV-VIS Spectral Atlas. This compaarison was facilitated by converting absorbance (by wavelength) into absorbance cross-sections (cm2/molecule). Resultant cross-section references from the present study agree well with the Mainz reference spectra, except in the case of Dichloromethane. Additionally, a limit of detection for most of the compounds analyzed was determined using varying approaches. The limits of detection from this analysis were compared with the manufacturer specified limits of detection.