SUPERCRITICAL-FLUID EXTRACTION COUPLED WITH ENZYME-IMMUNOASSAY ANALYSIS OF SOIL HERBICIDES

Supercritical fluid extraction (SFE) was coupled with enzyme immunoass ay;analysis (EIA) for the analysis of the following herbicides, 2,4-ph enoxyacetic acid (2,4-D), 2-chloro-4,6-bis(ethylamino)-s-triazine (sim azine), 2-chloro-4-ethylamino-6-propylamino-s-triazine (atrazine) and -chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide (alachlor) in soil and compared with liquid vortex extraction (LVE), Five soils, ranging in texture from sandy;loam to silty clay were fortified with 500 ng g( -1) of herbicide, allowed to air dry, and extracted using supercritica l fluid or LVE, Atrazine and alachlor were also fortified at 50 ng g(- 1), Field-weathered soils, with incurred residues from field applicati on, were also extracted, EIA of herbicides using a microtitre plate fo rmat were in good agreement with GC and HPLC results (r(2) = 0.95), SF E was performed using a Dionex (Sunnyvale, CA, USA) Model 703 extracto r in the dynamic mode at 20.3 MPa and 66 degrees C for 3 min, followed by 34.4 MPa extraction for 17 min, SFE recoveries with unmodified CO2 were 7, 56, 57, and 83%, respectively, for 2,4-D, simazine, atr;azine and alachlor, Recoveries improved to 101, 79, 90, and 88% for 2,4-D, simazine, atrazine and alachlor, respectively, by adding 1.5 ml of tri ethylamine to a 100 ml acetone-water (9 + 1) modifier Collection of an alytes by SFE was improved by using C-18 solid-phase traps (90% recove ry) compared to liquid acetone collection results (65% recovery).