EVALUATION OF ATRAZINE SOIL EXTRACTION METHODS FOR THE DETERMINATION BY ENZYME-IMMUNOASSAY AND GAS-CHROMATOGRAPHY

Four soil extraction methods were evaluated for the determination of a trazine and other s-triazines by ELISA and GC, using both field-treate d and laboratory fortified samples. The most efficient recoveries for atrazine, simazine, and cyanazine from loam soil fortified at concentr ations from 0.01 ppm to 1 ppm were obtained by mechanical wrist-action shaker (1 h) using methanol:water and solid phase extraction (SPE) cl eanup (standard method). A handshaking extraction(1 min) with acetonit rile:water showed fairly good correlation with the standard extraction method and is suitable for field use with ELISA. Sonication using ace tonitrile:water and SPE cleanup was the most efficient extraction meth od for the dealkylated metabolites (deisopropyl and deethyl atrazine) with recoveries higher than 60%. In general, supercritical fluid extra ction (SFE) was as efficient as sonication and handshaking but was mor e variable. A guideline for validation of immunoassays and methods com parison is given. The sensitivity of the ELISA method was comparable t o the GC and was both accurate and precise. Comparison of ELISA and GC determinations of 120 field soil samples and 40 laboratory spiked soi l samples extracted with four different methods showed no false negati ves or positives with excellent correlations and showed not significan t differences (P>0.05). An evaluation of the cost for GC and ELISA met hods was also conducted.