Optimizing nitrogen-phosphorus detector gas chromatography for pesticide analysis
1995
Draper, W.M.
The goal of this work was to improve the performance of the nitrogen-phosphorus detector gas chromatograph (NPD-GC) for multiresidue pesticide analysis. Severe tailing of phosphorus pesticides was found to be associated with the NPD (or thermionic ionization source) and not the column as demonstrated by matched separations using a flame photometric detector (FPD). The "source tailing" of phosphorus compounds in NPD increases as the source ages and can be reduced or eliminated by recoating the source with rubidium and alumina powder. Response to phosphorus pesticides increased 2-20-fold or more by rinsing the capillary column with organic solvents, but response factors for nitrogen-containing pesticides were unchanged by this treatment. Column tailing of polar pesticides (triadimefon, carboxin, norflurazon, bromacil, hexazinone, fenarimol, fluridone, and simazine) also was reduced by column cleaning. The fewest coelutions (for pesticides analyzed by U.S. EPA Method 507) were found with a methyl silicone capillary column.
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