The article describes an aptamer affinity column for selective solid-phase extraction of aflatoxin B2 (AFB2). Amino-modified aptamer
against AFB2 was immobilized on CNBr-activated Sepharose through a covalent bond. The effects of oligosorbents based on 3′- or
5′-amino-modified sequences with a C6 or a C7 spacer arm were evaluated by UV spectroscopy at 260 nm. The extraction recovery
was evaluated by HPLC with fluorometric detection. The extraction of AFB2 was optimized. Under the optimum conditions, the
aptamer affinity column has a linear response to AFB2 in the range of 0.5–80 ng, with a capacity of 84.6 ng. Control supports without
immobilized aptamers and a nonspecific oligosorbent immobilized with a negative control oligonucleotide were studied in order to
demonstrate selectivity. The method was tested with spiked peanut sample (0.5–50 μg·kg−1 AFB2) and gave average recoveries of
80.9% and a mean relative standard deviation of 1.9%. The limit of detection is 25 pg·mL−1. This is much lower than the maximum
residue limits suggested by the European Union. The columns can be re-used up to five times without any loss of performance. The
oligosorbent was also applied to clean-up of AFB2 from peanut sample extracts before HPLC analysis. Results were further
confirmed by ultra-fast liquid chromatography with tandem mass spectrometry. Conceivably, the method may also be applied to
other samples, such as food, agricultural products, and traditional Chinese medicines.

• An oligosorbent-based aptamer affinity column for selective extraction of aflatoxin B2 prior to HPLC with fluorometric detection