Establishment of analytical method and monitoring for determination of pesticide residues in collected honey samples

Three different analytical methods were used in this investigation to choose the suitable method with high recovery to validate an analytical method for pesticide residues in honey samples. The systems of GC/NPD and GC/ECD were used to measure recoveries from spiked samples. The honeybee samples free from residues were spiked at one level and the recoveries of pesticides were studied. Spiked level was settled according to the detectors sensitivity to test pesticides in the range of 0.05 – 1.0 μg/g. The three tested analytical methods gave relatively high recoveries for the tested pesticides (84.1-99.5%) with standard divisions varying from ± 8 to 10.7% for different pesticides. The percent mean recoveries of tested pesticides in the 1st, 2nd and 3rd analytical method were 92.3, 84.1 and 99.5%, with standard deviations ±10.7, 9.8 and 8.0%, respectively. In general, the recoveries obtained with the third analytical method were always higher than those obtained with the first and second analytical methods, with low standard deviations. All the collected honey samples during two years were free from any pesticides contamination except one sample was obtained at year 2005 from Ehnasia district of Bani Suwayf Governorate. This sample was contaminated with the insecticide chlorpyrifos -ethyl at concentration 0.02 μg/g (below the quantification limit 0.05 μg/g). The presence of residue of such compound in the samples analyzed may be attributed to intensive use of chlorpyrifos -ethyl in cotton fields in controlling the cotton leaf worms and cotton boll worms.