DETERMINATION OF THIAZOPYR AND ITS METABOLITE IN FLORIDA GROUNDWATER USING GRAPHATIZED CARBON SOLID-PHASE EXTRACTION AND LIQUID-CHROMATOGRAPHIC DETERMINATION

A study comparing two liquid-solid extraction methods for the analysis of thiazopyr and its monoacid metabolite in groundwater is reported. Method A is a modification of a method developed by the Monsanto Co. w hich is based on liquid-solid extraction with silica-based octadecyl ( C-18) extraction disks followed by gas chromatographic (GC) determinat ion. Method B was developed in our laboratory and is based on liquid-s olid extraction with graphatized carbon black followed by highperforma nce liquid chromatographic determination. Using method B, the parent a nd acid metabolite of thiazopyr are analyzed simultaneously without th e need for metabolite derivatization. Subsequent GC confirmation and q uantification are achieved through solvent exchange and derivatization of acid metabolite using the same sample extract. Recovery studies at 1.0, 5.0, and 10.0 ppb indicated excellent percent recovery for thiaz opyr, 88 +/- 13, 95 +/- 3, and 92 +/- 5; and for thiazopyr monoacid, 1 04 +/- 10, 100 +/- 6, and 101 +/- 3, both respectively. Method detecti on for each compound is 1.0 ppb.