Ochratoxin A in dried vine fruit: method development and survey

A method is described for the determination of concentrations of the mycotoxin ochratoxin A in dried vine fruits (currants, raisins and sultanas) using acidic methanolic extraction, immunoaffinity chromatography clean-tip and HPLC determination. The limit of detection was estimated as 0.2 mu g/kg, and recoveries of 63-77% were achieved at 5 mu g/kg. HPLC-mass spectrometric confirmation of the identity of ochratoxin was obtained. Ochratoxin A and aflatoxins were determined in 60 samples of retail dried vine fruits purchased in the United Kingdom. Ochratoxin A was found in excess of 0.2 mu g/kg in 19 of 20 currant, 17 of 20 sultana and 17 of 20 raisin samples examined, an overall incidence of 88%. The maximum level found was 53.6 mu g/kg. No aflatoxin was found in any sample analysed, using a method with a detection limit of 0.2 mu g/kg for each of aflatoxin B-1, B-2, G(1) and G(2).