Atomic emission detection for gas chromatographic analysis of nitrogen-containing herbicides in water

A gas chromatography-atomic emission detection (GC-AED) system was used to analyze nitrogen-containing herbicides. Two methods of sample preparation were used to demonstrate the system's applicability. Method 1 was U.S. Environmental Protection Agency (EPA) Method 507. Method 2 was a modification of EPA Method 507 using larger sample volumes and smaller extract volumes to yield compound detection levels 30 times lower than detection levels from method 1. Analysis of replicate reagent water spikes with method 1 gave analyte recoveries ranging from 82 to 107%, with standard deviations of recovery of not more than 6.7%. Method 2 gave recoveries ranging from 50 to 112%, with a standard deviation of recovery of not more than 33%. A loss in recovery and precision with method 2 compared with method 1 was attributed to loss of more volatile analytes during extract concentration. Selectivity was demonstrated with solvent spiked with fuel oil and atrazine. Response factors generated with the GC-AED system showed compound-independent elemental linearity for analytes. Relative standard deviations of not more than 5.34% were obtained for 3 elements tested: nitrogen, sulphur, and chlorine. An elemental calibration mixture was prepared to validate traditional methods of quantitation. Samples were analyzed for nitrogen-containing herbicides, which were quantitated with both an analyte calibration and an elemental calibration, and results were compared.