The first fully optimized and validated SPE-LC-MS/MS method for determination of the new-generation neonicotinoids in surface water samples

Abstract

Widespread use of the new generation neonicotinoids (NQs) results in their constant inflow to water bodies. Both their persistence in waters and mechanism of action similar to older compounds already banned in the EU raise concerns about potential ecotoxicological effects. Information about presence of the new NQs in the aquatic environment is still sparse, and the consequences for aquatic organisms remain mostly unknown, due to the lack of sensitive and selective analytical tools. Therefore, a method utilizing solid-phase extraction and liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) has been developed and optimized, enabling the monitoring of EU-approved NQs: acetamiprid (ACT), sulfoxaflor (SFX) and flupyradifurone (FLU), and common NQ metabolite 6-chloronicotinoic acid (6-CNA) in surface waters. To optimize their extraction from natural water samples, the response surface methodology (RSM) was used. An increase in pH value favored higher absolute recoveries (AR) of ACT, SFX and FLU, while the opposite effect was observed for 6-CNA. Increasing water sample volume had adverse effect on the extraction of all compounds. The optimal conditions for simultaneous extraction of all compounds included the use of Oasis HLB sorbent, 200 mL of a water sample at pH of 4.6, and application of 0.3% HCOOH in acetonitrile as an eluent, allowing to obtain AR values above 80% in most cases. Further increase in pH value had positive impact on extraction effectiveness of ACT, SFX and FLU. The method was subjected to full matrix-matched validation and was proven to be fully reliable for the analysis of ACT, SFX and FLU, while the successful isolation of 6-CNA depends on the matrix composition. Finally, the method was applied to the analysis of NQs in surface water samples, proving its sensitivity and selectivity. It can be easily adapted as a tool for trace analysis of NQs and for NQ-associated risk assessment in aquatic ecosystems.

Keywords: LC-MS/MS; Neonicotinoids; Response surface methodology; Solid phase extraction; Surface waters.