Determination of Aflatoxin B₁ in Environmental Water by Ultra-High Performance Liquid Chromatography after Solid Phase Extraction with Composite Ionic Liquid Modified Silica Gel Nested Sponge Material

Composite ionic liquid prepared by functionalization of ionic liquids was used to modify silica gel nested sponge materials, and properties of the composite material were characterized by field emission scanning electron microscopy and Fourier transform infrared spectrometer. Composite materials were loaded into a disposable sterile syringes to prepare solid phase extraction column, adsorption capacity of which was investigated. After impurity removal and filtration of the water sample, 1.5 L of the continuation filtrate was taken and passed through the prepared solid phase extraction column at flow rate of 3 mL·min⁻¹. The column was rinsed by 5 mL of water and eluted by 3 mL of mixed solution of acetone and 2 mol·L⁻¹ hydrochloric acid solution at volume ratio of 1∶5. The eluate was collected and passed through a 0.45 μm organic filter membrane, and the filtrate was analyzed according to chromatographic conditions. Eclipse Plus C₁₈ chromatographic column was used as the stationary phase, and aflatoxin B₁ (AFB₁) was separated by isocratic elution with the mixed solution of water and acetonitrile-methanol solution (volume ratio of 1∶1) at volume ratio of 68∶32 as the mobile phase, and detected by the fluorescence detector. It was shown that the sponge skeleton with the six ring network structure and the silica gel large particle material modified with ionic liquids in the synthesized composite material nested together, forming a structure similar to reinforced concrete, which combined the good selectivity of ionic liquids and the mechanical flexibility of sponges. The prepared solid phase extraction column had an adsorption capacity of 26.48 mg·g⁻¹ for AFB₁, significantly higher than the aflatoxin adsorption capacity (0.460-4.289 mg·g⁻¹) of adsorption materials reported in literatures. Linear relationship between values of the mass concentration and the peak area of AFB₁ was kept in the range of 0.1-40 μg·L⁻¹, and the lower limit of determination was 0.2 ng·L⁻¹. Test for recovery was made according to the standard addition method, giving recoveries in the range of 75.2%-95.3%, and RSDs (n=6) of the determined values ranged from 6.9% to 8.4%.