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.