A dispersive solid phase extraction adsorbent based on aptamer modified chitosan nanofibers for zearalenone separation in corn, wheat, and beer samples

Highly selective separation of trace bio-toxins in food samples has long been a hot topic pursued by analytical chemists. In this paper, chitosan nanofibers prepared by freeze-drying were modified with aptamers for dispersive solid phase extraction (dSPE) of trace zearalenone. The morphology of achieved chitosan nanofibers was found to be uniform and continuous, and the length was at the micron level with about a 400 nm diameter. The immobilization capacity of the aptamer was as high as 10.1 μg on 5 mg chitosan nanofibers with good stability and repeatability, owing to the high specific surface area of nanofibers. The aptamer modified chitosan nanofibers (Apt-CNFs) showed specific selectivity to zearalenone with a selectivity coefficient of 2.65 compared to the scrambled oligonucleotide functionalized CNFs, and the selectivity factors over other analogs and reference compounds were from 1.57 to 50.0. After the optimization of extraction conditions, the Apt-CNF based dSPE was coupled with high-performance liquid chromatography for zearalenone monitoring, and a good linear range of 0.06-10.0 μg L-1 was achieved with a detection limit of 18.0 ng L-1. The spiking recoveries of 101-108%, 100-110%, and 98.3-101% were achieved for trace zearalenone in corn, wheat, and beer samples, respectively. The residual zearalenone was detected in corn and wheat with a content of 0.365 and 0.0775 μg g-1, respectively.