Impact of dispersive solid-phase extraction on multi-residue pesticide analysis in honey bees

Abstract

The QuEChERS method is one of the most popular methods to analyse pesticides in food. In recent years, it was also established in the protection of bees, as plant protection products (PPPs) are still involved in bee poisoning incidents. An additional purification step using dispersive solid-phase extraction (dSPE) is often considered necessary to obtain sufficiently pure sample extracts and increase sensitivity. Our aim was to improve the existing QuEChERS method based on honey bees, using 273 active substances and to determine differences between purification with dSPE and without.

The results show that 271 substances can be detected using either dSPE, without purification, or both. Pentachlorophenol and dichlobenil were the only substances that were not detectable using both methods. Over 70% of the active substances achieved recoveries between 70 and 120%. However, it turned out that there were more substances that did not reach the limit of acceptable recovery after purification with dSPE.

The excellent sensitivity of both methods was demonstrated by the limit of detection and quantification (LOD, LOQ), which coincided in approximately 40% of cases. For the remaining 60% of active substances, LODs and LOQs differed by one calibration point up or down for both methods. Regardless of the method, the most frequent LOQ was 10 µg/kg for LC-MS/MS and the LOQ for GC-MS(/MS) was 100 µg/kg with dSPE and 200 µg/kg without dSPE.

We can conclude that by using the improved method further purification steps are not necessarily required to reliably determine the ingredients within our analytical spectrum.

In fact, it even turned out that for substances that are sometimes toxic to bees, it is better not to further purify analytical samples. This adapted method saves time and costs in routine laboratory work and can be easily adapted to other analytes or research questions.