Analysis of fire ant pesticides in water by solid-phase microextraction and gas chromatography/mass spectrometry or high-performance liquid chromatography/mass spectrometry

The analysis of four widely used fire ant pesticides (chlorpyrifos, fenoxyc arb, avermectin, and hydramethylnon) in water was accomplished by combining solid-phase microextraction (SPME) with either gas chromatography/quadrupl e ion trap mass spectrometry (GC/MS) or high-performance liquid chromatogra phy/quadruple ion trap MS (HPLC/MS). Solid-phase mi croextraction is a fast . selective, and solvent-free extraction technique that accomplishes both e xtraction and pre-concentration events in a single step. These features all owed the methods developed to be sensitive, with calculated LOD of 10ng/l f or chlorpyrifos, 80 ng/l for fenoxycarb. 100 ng/l for avermectin, and 1 mug /l for hydramethylnon, each obtained from only 10 min extractions from stan dards in water. These values represent an improvement of an order of magnit ude in detection limits for avermectin and hydramethylnon compared to those reported previously. The methods were shown to be linear in the range of 1 00 ng/l-100 mug/l for chlorpyrifos and fenoxycarb, 1 mug/l mg/l for avermec tin, and 10 mug/l(-1) mg/l for hydramethylnon. These methods were applied t o the analysis of water samples to which commercial fire ant bait preparati ons had been added and to runoff water collected from a lawn. Quantitative analyses were performed for chlorpyrifos, fenoxycarb, and avermectin, as th e pesticides in the water samples were monitored for similar to9 days to al most 2 months. However, due to poor precision of the method for hydramethyl non, only qualitative data were obtained. (C) 2001 Elsevier Science B.V. Al l rights reserved.