Magnetic Solid Phase Extraction Based on Ionic Liquid Coated Fe3O4-Grafted Multi-Walled Carbon Nanotubes for Determination of Sulfonamides in Environmental Water Samples

In combination with high performance liquid chromatography-photodiode array detector (HPLC-PDA), a vortex-assisted magnetic solid phase extraction method with the 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) ionic liquid coated Fe3O4-grafted multi-walled carbon nanotubes (IL-Fe3O4 @ MWCNTs) as the magnetic adsorbent was developed for the determination of four sulfonamides including sulfamethazine, sulfisoxazole, sulfadoxine, and sulfameter in environmental water samples. The optimal conditions for analysis were as follows: 20.0 mg of IL-Fe3O4 @ MWCNTs was dispersed into 200 mL of water sample under vortex for 15 min. Then, the IL-Fe3O4 @ MWCNTs carrying sulfonamides was separated from the water sample by an external magnetic field. Next, the sulfonamides were eluted from IL-Fe3O4 @ MWCNTs with 3.5 mL of 1.0% ammonium acetate methanol solution. Finally, the eluent was dried under a mild stream of nitrogen and reconstituted in 300 mu L of methanol for the subsequent HPLC-PDA analysis. Under the optimized conditions, an excellent linearity was observed in the range of 0.375 - 75.0 mu g/L for the four sulfonamides, with the correlation coefficients ranging from 0.9985 to 0.9996. The limits of detections (S/N = 3) ranged from 0.079 to 0.099 mu g/L. The mean recoveries at three spiked levels ranged from 80.60% to 99.99%. The relative standard deviations (RSDs) of intra-day and inter-day varied from 1.3% to 6.9% and from 1.2% to 2.9% (n = 3), respectively. The proposed method was demonstrated to be simple and feasible for the trace analysis of sulfonamides in environmental water samples.