Determination of abamectin in soil samples using high-performance liquid chromatography with tandem mass spectrometry.

Abamectin, which is comprised of a mixture of avermectins B1a and B1b, is a natural pesticide used as an anti-parasitic agent in livestock, ornamental, and agricultural crops, which can potentially be transported to aquatic systems. These compounds are highly toxic to both aquatic vertebrates and invertebrates at low concentrations in water. This investigation developed high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) techniques to support automated extraction by an accelerated solvent extraction (ASE) system and chromatographic techniques to measure residues of avermectins in complex soil samples. HPLC along with atmospheric pressure chemical ionization (APCI) MS/MS was used for separation and determination of avermectin isomers in soil samples. Average method recovery for abamectin by UV was 91%, while detection by MS/MS resulted in a 68% recovery for abamectin. Individual method recoveries by MS/MS were 53.6% for avermectin B1a and 36.8% for avermectin B1b. The use of tandem technology eliminated matrix interferences and resulted in an approximately eight-fold increase in sensitivity.