MATRIX-ISOLATION FOR TRACE ATMOSPHERIC GAS ANALYSIS
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Date
1999
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Ohio State University
Abstract
The aim of this work is to develop a reliable field method for trace atmospheric gas analysis using FTIR spectroscopy of carbon dioxide matrices. Calibration curves of the intensity of IR absorptions of a number of compounds isolated in $CO_{2}$ matrices at 77 K (liquid nitrogen temperature) over a range of concentrations were set up; linear responses were obtained and it was found that $NO_{2}$ could be detected at a minimum atmospheric concentration of ca. 33 ppb, $SO_{2}$ at a level about 10 times greater than this and the carbonyl compounds acetone, acetaldehyde, acetic acid and formic acid at levels of about 3.3 ppm. Various methods of separating these trace gases from atmospheric samples have been investigated; these include the use of traps held at different temperatures and of a range of adsorbent materials (activated carbon, alumina, kieselguhr and molecular sieve). Activated carbon gives the best separation of the methods studied: e.g. it can provide a quantitative separation of acetone/acetaldehyde from a mixture with $CO_{2}$. The method has been applied to field samples collected at two locations: (i) the car park of the Reading University Chemistry Department: (ii) Shinfield Road - a busy town street located just off the Reading University Campus. The results provide useful qualitative information, showing very clearly the build-up of carbonyl compounds between 5-6 a.m. when the first samples were taken and 8-9 a.m. as the morning traffic increases. With further calibration experiments it is possible that quantitative data could also be obtained from these experiments.
Description
Author Institution: Department of Chemistry, University of Reading