Determination of abamectin in some forest matrices by liquid chromatography with fluorescence detection

A liquid chromatographic method was developed and validated for the determination of abamectin B 1a residues in some terrestrial (balsam fir and oak foliage, sandy and clay loam soils and leaf litter) and aquatic (stream water and sediment) forest matrices. The processed foliage, soil, litter, and sediment were fortified with abamectin and extracted with ethyl acetate. The fortified steam water was extracted with dichloromethane. Aliquots of crude extracts were cleaned with Florisil® column chromatography and the purified extracts were derivatized using 1-methylimidazole and trifluoroacetic anhydride. The derivatized abamectin was analysed by reverse phase liquid chromatography, with a fluorescence detector set at 232 nm excitation and 461 nm emission wavelengths. A Spherisorb® ODS2, 5μm, 250 × 4 mm column was used. The samples were run isocratically using methanol-water as the mobile phase. Mean recoveries for the analyte ranged from 83.0 to 93.0%, with a coefficient of variation from 6.3 to 12.4%. Limits of detection and limits 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 corresponding values were 0.003 and 0.009 ng/mL. The procedure provides a reliable and sensitive method for determining abamectin B 1a residues in forest matrices.