Evaluation of co-solvents with supercritical fluid extraction of atrazine from soil

Supercritical fluid extraction (SFE) with CO2 has been successfully applied to herbicide extractions from soil. The objectives of this work were to co mpare extraction efficiency of atrazine from soil using different types and quantities of co-solvent modifiers under a specified set of SFE instrument conditions and to determine the ruggedness of an optimized extraction prog ram and co-solvent on several soils with varying characteristics. The effec t of 18 co-solvents on atrazine extraction from Lufkin fine sandy loam was determined using a completely randomized design with six replications. Extr actions of Luflcin soil using the more nonpolar co-solvents had recovery si milar to extractions where no co-solvent was added. The co-solvents that sh owed high extraction efficiency, low incidences of restrictor plugging, and ease of cleaning extraction cells were acetone, acetone:water mixtures (wi th and without 1% triethylamine), and acetonitrile. The addition of 1% trie thylamine (TEA) did not increase recovery significantly. The 9:1 acetone:wa ter mixture with 1% TEA was used for the soil comparison because of the hig h atrazine recovery and low water content. No differences in atrazine recov ery were detected between extractions of the four representative soils when the same extraction conditions were employed. No cleanup steps were includ ed in the procedure, yet adequate chromatography results were obtained sugg esting some selectivity for this procedure. These data indicate that SFE wi th optimized conditions and appropriate co-solvents is a relatively robust method that can effectively be used in soil extractions of atrazine.