Development of an oligosorbent for detection of ochratoxin A

Ochratoxin A, a mycotoxin produced by the genera Aspergillus and Penicillium, is a contaminant of food products. One method for the detection of this toxin when it is present at low levels is based on the use of commercial immunoaffinity columns clean-up to concentrate the compound, followed by high-performance liquid chromatography with fluorescence detection. An alternative approach is to replace the antibodies with DNA aptamers. Accordingly, a DNA aptamer with high affinity and specificity for ochratoxin A was graft (DNA concentration 0.2 mg/ml) to cyanogen bromide-activated sepharose (35 mg) and used as sorbent for the preparation of solid phase extraction columns. This oligosorbent was optimised for the selective extraction of Ochratoxin A from beer samples. After the immobilisation of the aptamers on a solid support, the Ochratoxin A extraction procedure was performed. Spiked beer was degassed, then diluted and applied to the oligosorbent. The toxin was eluted from the oligosorbent and quantified using high-performance liquid chromatography with fluorescence detection. An average recovery of (96%) and a mean RSD of (2.2) for the spiked beer sample in the range of (1–3 ng/ml) were obtained. Aptamer solid phase extraction columns could be re-used more than three times without any loss of performance. This method allowed fast and reliable analysis of beer samples with an estimated limit of detection of 0.2 ng/ml from a sample volume of 200 μL