Miniaturization of the SWIEET extraction method to assess the body burden of carbendazim in Chironomus riparius midges after metamorphosis

For the analysis of micropollutants in biota samples such as insects with aquatic life stages with inherently low body weight, miniaturization of common extraction methods is necessary. For QuEChERS extractions, miniaturization down to a few individual organisms was reported for invertebrates. For the investigation of interindividual differences in insects, even further miniaturization is necessary. Our salt-free SWIEET extraction method recently developed as an alternative to QuEChERS was originally optimized for a total volume of 5 mL. To enable the determination of carbendazim in midges, that weigh between 0.3 and 0.5 mg, the method required miniaturization. Using a model analyte mix, we investigated how reducing the total extraction volume affected analyte recoveries and investigated matrix effects using Chironomus riparius as model organisms. The miniaturized SWIEET extraction was then applied to the analysis of the pesticide carbendazim in adult midges of Chironomus riparius from an exposure experiment at the larval stage. Since matrix effects played a significant role in the extraction of carbendazim, particularly for samples from lower exposure concentrations, sample preparation and calibration modes had to be further optimized. With the final protocol, we were able to successfully extract carbendazim from single midges. The effects of pooling midges were investigated to better understand matrix effects and effects on robustness. With the optimized and miniaturized method, we achieved repeatable results, making it suitable for determining carbendazim loads in midges and correlating them to the exposure concentrations.