Trace level determination of pyrethroid and neonicotinoid insecticides in beebread using acetonitrile-based extraction followed by analysis with ultra-high-performance liquid chromatography-tandem mass spectrometry.

Beebread is among the matrices suspected of contaminating honeybee. To better understand this contamination, the study aimed to develop an efficient, sensitive and reliable analytical method for the trace analysis of pesticides in beebread. This study focuses specifically on the insecticides pyrethroids and neonicotinoids and some of their metabolites. It describes the development and validation of an original analytical approach that consists of one simple extraction method based on modified QuEChERS followed by a selective and sensitive analysis by UHPLC-MS/MS to determine the target compounds in beebread. The method was validated using a quadratic fit. RSD values below 20% were obtained, except for 5-hydroxy-imidacloprid and imidacloprid at 0.5 ng/g, which exhibited RSDs of 25% and 21%, respectively. The intra-day precision was less than 10% for many of the investigated compounds. The inter-day precision varied between 2% and 36%, depending on the compound and the concentration. The recoveries varied from 53% to 119%, with averages of 83, 81 and 77% for the extraction of beebread samples spiked at 0.5, 5 and 10 ng/g, respectively. The LOD values for all the substances were below ng/g, with the exception of 6-chloronicotinic acid (LOD=1.7 ng/g). The method was then applied to the analysis of 32 beebread samples and revealed the presence of 7 of the target substances. The most frequently detected pesticides belonged to the neonicotinoid family and were generally present at low concentrations, but in some cases exceeded 170 ng/g (acetamiprid and thiacloprid). Some pyrethroids were also detected (lambda-cyhalothrine and bifenthrine), but at very low levels.