Screening of pesticide residues in honeybee wax comb by LC-ESI-MS/MS. A pilot study

A developed multi-residue method using microflow-LC-ESI-QqQ-MS provided a wide-scope analysis for medium-polar and polar pesticide residues (120 compounds including breakdown products). Honeybee wax comb samples were extracted using a generic QuEChERS based procedure. Acceptable recoveries at concentration levels of 5 and 50 μg kg−1 were within the 70–120% range with an associated precision RSD <20%. The LOQ values were mostly 5 μg kg−1 for almost all pesticides. Aprox. 31 of 120 LC-amenable pesticides tested (25.8%) were detected in a pilot study of 60 samples. Pesticide residues detected using the proposed method were the breakdown products of amitraz, DMPF and DMF, an acaricide used for Varroa mite control, with a range of concentration from 5 to 464 μg kg−1 (sum of DMPF + DMF), organophosphate insecticides from 1 to 464 μg kg−1, acaricides at concentrations > 9 μg kg−1; fungicides at concentrations ranging from 1 to 23 μg kg−1. The number of positive detections due to herbicides was lower as expected and at a lower level of concentration, from 1 to 5.9 μg kg−1. © 2016 Elsevier Ltd