DETERMINATION OF ABAMECTIN IN SOME FOREST MATRICES BY LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

A liquid chromatographic method was developed and validated for the de termination of abamectin B-1a residues in some terrestrial (balsam fir and oak foliage, sandy and clay loam soils and leaf litter) and aquat ic (stream water and sediment) forest matrices. The processed foliage, soil, litter, and sediment were fortified with abamectin and extracte d with ethylacetate. The fortified steam water was extracted with dich loromethane. Aliquots of crude extracts were cleaned with Florisil(R) column chromatography and the purified extracts were derivatized using 1-methylimidazole and trifluoroacetic anhydride. The derivatized abam ectin was analysed by reverse phase liquid chromatography, with a fluo rescence detector set at 232 nm excitation and 461 nm emission wavelen gths. A Spherisorb(R) ODS2, 5 mu m, 250 x 4 mm column was used. The sa mples were run isocratically using methanol-water as the mobile phase. Mean recoveries for the analyte ranged from 83.0 to 93.0%, with a coe fficient of variation from 6.3 to 12.4%. Limits of detection and limit s of quantitation for solid matrices ranged from 0.10 to 0.20 and from 0.30 to 0.60 ng/g, respectively, and for stream water the correspondi ng values were 0.003 and 0.009 ng/mL. The procedure provides a reliabl e and sensitive method for determining abamectin B-1a residues in fore st matrices.