DETERMINATION OF TRIASULFURON IN SOIL - AFFINITY-CHROMATOGRAPHY AS A SOIL EXTRACT CLEANUP PROCEDURE

Triasulfuron forms one of the group of sulfonylurea herbicides. These are used widely for controlling weeds as they are effective at very lo w application rates. This effectiveness is responsible for the crop lo sses due to persistence of trace amounts of the herbicides (less than or equal to 100 pg/g) in the soil. The numerous immunoassays described have been constrained by the fact that the soil extract contains co e xtractants which interfere in the assays, so much so, that these assay s are useless at low levels of herbicide. We describe here the prepara tion and application of an immunoaffinity column which binds specifica lly to triasulfuron, thus cleaning up the soil extract. The experiment design is such that this also leads to concentration of the triasulfu ron, making it easier to assay reliably using ELISA. Six different soi l types were used to validate this procedure. In most cases, the herbi cide content could be detected at 100 pg/g (critical phytotoxic herbic ide level in soil) with a variation of +/- 20% in the readings.