Enhancement of electron-capture detection of methyl bromide in air by iodination.
An instrumentally simple and cost-effective method for the direct analysis of methyl bromide in ambient air is described. The method is based on the separation of sample components by gas chromatography, the conversion of methyl bromide to methyl iodide by reaction with an inorganic iodide salt, and the detection of the methyl iodide thereby produced by an electron-capture detector. Of the 20 different inorganic salts investigated here for conversion of methyl bromide to methyl iodide, zinc iodide was found to provide the greatest conversion efficiency. In addition, zinc iodide was found to provide high conversion efficiency at a modest reaction temperature, thereby minimizing both the thermal decomposition of compounds within the reaction volume and the level of column bleed introduced to the detector. The reactions of several other brominated and chlorinated organic compounds with zinc iodide have also been characterized. The successful application of this instrument to the quantitative determination of methyl bromide in a local background air sample is then demonstrated.
Hughes
R A
RA
Department of Chemistry, Montana State University, Bozeman 59717, USA.
Knighton
W B
WB
Grimsrud
E P
EP
D000388:Air / Q000032:analysis*; D004583:Electrons; D006842:Hydrocarbons, Brominated / Q000032:analysis*; D007455:Iodine / Q000737:chemistry*
D006842:Hydrocarbons, Brominated; D007455:Iodine; C005218:methyl bromide