Simultaneous determination of neonicotinoid insecticides and metabolites in rice by dispersive solid-liquid microextraction based on an in situ acid-base effervescent reaction and solidification of a floating organic droplet.

A sensitive and rapid method named dispersive solid-liquid microextraction combining in situ acid-base reaction-based effervescence and solidification of a floating organic droplet was developed for the simultaneous determination of eight neonicotinoid insecticides and two metabolites in rice by ultra-performance liquid chromatography-tandem mass spectrometry. The samples were extracted with sodium citrate monobasic-modified acetonitrile by vortexing and purified by primary secondary amine, and then a mixture of 1-undecanol and sodium carbonate aqueous solution was rapidly injected. An acid-base reaction and carbon dioxide bubbles were generated in situ, which promoted the dispersion of 1-undecanol droplets and subsequent transfer of the analytes from the acidified acetonitrile extract to 1-undecanol. The 1-undecanol phase was easily retrieved by centrifugation and solidification in an ice bath. This novel dispersive solid-liquid microextraction fully utilized the advantages of the effervescent reaction and floating droplet solidification, which was carried out in a tube and did not require stepwise analysis for a solid matrix. Under the optimized conditions, the average recoveries of the analytes ranged from 77.8 to 97.1% with relative standard deviations less than 7.3. The limits of detection varied between 0.01 and 0.1 µg kg-1, and enrichment factors were 42-55. The proposed method provides a quantitative, sensitive, and convenient analytical tool applicable for routine monitoring of neonicotinoids in rice. Graphical abstract ᅟ.