The development, validation and application of a GC-dual detector (NPD-ECD) multi-pesticide residue method for monitoring bee poisoning incidents.

A simple multiresidue method based on matrix solid phase dispersion (MSPD) combined with clean-up has been developed for the simultaneous screening of 153 pesticides in honeybees suspected of suffering from pesticide poisoning during field spraying. Extraction and clean-up were carried out in a glass column containing anhydrous sulphate, 2.0g of octadecyl (C18) and a 2.0-g sample of bees (23 insects on average) macerated with 4.0g of Florisil. An additional layer of anhydrous sodium sulphate was added, and acetonitrile was used as the elution solvent. This combination of clean-up steps ensured an efficient purification. A gas chromatograph with dual selective detectors for electron capture and nitrogen-phosphorous was used. The results presented in this paper demonstrate that matrix solid-phase dispersion (MSPD) with the one-step clean-up procedure is the most effective extraction technique. MSPD method recoveries ranged from 70 to 118%, with precision values expressed as a relative standard of <20%, except for 10 pesticides that had recoveries of 50-70% and two with 120-130%. Low limits of detection (0.003-0.04μg/g) and quantification (0.005-0.05μg/g) were readily achieved with this method for all tested pesticides. A "top down" empirical model was used to estimate the expanded uncertainty at 28% on average (coverage factor k=2, confidence level 95%). The MSPD method was successfully used on real bee samples to analyse four acaricides, 55 fungicides, 16 herbicides and 78 insecticides from various regions of Poland. A total of 33 honeybee samples from suspected pesticide poisoning incidents were analysed, in which 17 different pesticides were determined (14 insecticides and three fungicides). The pesticides most often found in honeybees were cypermethrin (in 51% of the samples, 0.008-0.563µg/bee), chlorpyrifos (27%, 0.001-51.5µg/bee) and biphentin (21%, 0.002-0.012µg/bee).