Ultra-high performance liquid chromatography combined with mass spectrometry for determination of aflatoxins using dummy molecularly imprinted polymers deposited on silica-coated magnetic nanoparticles

This article describes a method for determination of four aflatoxins by a combination of ultra-high performance liquid chromatography and mass spectrometry (UHPLC-MS/MS). Magnetic dummy molecularly imprinted polymers (md-MIPs) are used for fairly selective preconcentration. The preparation of the md-MIP involves (a) coating of magnetic nanoparticles (with a typical diameter of 200 nm) with a shell of silica, (b) modifying the surface with methacryloxy groups, and (c) creating a MIP on the surface by graft imprinting in aqueous solutions using 5,7-dimethoxycoumarin as the dummy template, and methacrylic acid and 4-vinylpyridine as the functional monomers. After elution of the template, the md-MIPs can be used for fairly selective extraction of the aflatoxins B1, B2, G1 and G2. Following magnetic separation of the particles, the aflatoxins were eluted and quantified by UHPLC-MS/MS. The limit of detection is 0.05 mu g center dot kg(-1) for aflatoxins B2 and G2, and 0.1 mu g center dot kg(-1) for aflatoxins B1 and G1. False-positive samples were identified by UHPLC-MS/MS in the positive ionization mode with multiple reaction monitoring.