Aptamer-targeted magnetic nanospheres as a solid-phase extraction sorbent for determination of ochratoxin A in food samples

► A sorbent based on aptamer for ochratoxin A and magnetic nanospheres were prepared. ► The oligosorbent was successfully applied to the clean-up of ochratoxin A from food samples. ► Performance of this oligosorbent was comparable to the C18 cartridge. ► Recovery results at spiking levels of 2.5–50 μg/kg were 67–90%. A sorbent based on the aptamer for ochratoxin A was immobilized onto magnetic nanospheres (MNS) and used to develop a magnetic solid-phase extraction procedure to clean up food samples in conjunction with high-performance liquid chromatography separation and fluorescence detection. Specific retention of ochratoxin A by the sorbent was demonstrated, and the capacity of the MNS–aptamer sorbent was determined. The efficacy of this new approach was successfully evaluated through comparison with solid-phase extraction on commercial C18 cartridge. Several different food samples fortified in the range of with 2.5–50 μg/kg yielded mean recoveries from 67% to 90%, respectively. Finally, this oligosorbent was applied to the selective extraction of ochratoxin A from unfortified food samples.