Zeolitic imidazolate framework-8 modified magnetic halloysite nanotube-based solid phase extraction for the analysis of carbamate pesticides by ultra-high performance liquid chromatography tandem mass spectrometry

Zeolitic imidazolate framework-8 modified magnetic halloysite nanotube (MHNTs@ZIF-8) composites were synthesized and evaluated for the first time as an efficient sorbent for the magnetic solid-phase extraction (mSPE) of carbamate pesticides (CPs) from water samples. MHNTs were prepared by coprecipitation, and MHNTs@ZIF-8 composites were assembled in situ at room temperature. After characterization, MHNTs@ZIF-8 was used to extract pirimicarb, propoxur, carbaryl, isoprocarb and fenobucarb via π-π stacking interaction and hydrophobic interaction between the imidazole skeleton of ZIF-8 and benzene rings or benzene-like rings in CPs, as well as the hydrogen bond formed between O in CPs and H in ZIF-8. The effects of the amount of sorbent, ionic strength, type and volume of desorption solvent and adsorption/desorption time were investigated. Under optimum conditions, good linearity was obtained for the analysis of CPs by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with R2 ≥ 0.9992. The limits of quantification range from 3 to 40 ng L-1 in water. Relative standard deviations (RSDs) were <7%, n = 5, within a batch and <9% among batches. The spiked recoveries were between 81 and 104%. The proposed method has been successfully applied to the determination of CPs in various water samples.