Comprehensive analysis of insecticides in melliferous weeds and agricultural crops using a modified QuEChERS/LC-MS/MS protocol and of their potential risk to honey bees (Apis mellifera L.).

The risk of exposure of honey bees to the presence of insecticides in melliferous plants is higher than previously reported. Therefore, monitoring insecticide residues in these plants is of great importance to honey bee safety. A novelty of the present research was the development of an innovative procedure for determination of residues of 142 insecticides in weeds and agricultural crops among melliferous plants. Phacelia, buckwheat, rape, common dandelion, cornflower and clover were selected for testing. Samples were extracted via QuEChERS. Two single sorbents (Z-Sep and Chitosan) and two combinations of sorbents (PSA/C18/ENVI-Carb/MgSO₄, PSA/GCB/MgSO₄) were tested. The matrix effect was applied as the main criterion for assessment of the method's effectiveness. The best sorbent for preparation of: (i) common dandelion samples was PSA/GCB/MgSO₄, (ii) rape, cornflower and clover samples - PSA/C18/ENVI-Carb/MgSO₄ sorbent and (iii) phacelia and buckwheat samples - Z-Sep sorbent. The developed procedure was applied for quantification of insecticide residues in 41 melliferous plant samples to estimate exposure of honey bees to pesticides through calculation of the hazard quotient (HQ). In total, 12 different insecticides were detected. The presence of neonicotinoid insecticides was found 7 times. The residues most frequently identified in melliferous plants were deltamethrin, dimethoate, and its metabolite, omethoate. An increased insecticide risk to honey bees was found for 4.9% and 9.8% of samples, for the oral and contact dose, respectively. This is why the hazard of melliferous plant residues was considered elevated for honey bees. The results clearly demonstrated that the approach developed provides reliable, simple and rapid determination of insecticides in melliferous plants, which is of great importance to honey bee safety.