Determination of ochratoxin A in grapes, dried vine fruits, and winery byproducts by high-performance liquid chromatography with fluorometric detection (HPLC-FLD) and immunoaffinity cleanup.

A liquid chromatographic method for the determination of ochratoxin A in grapes, dried vine fruits, and winery byproducts was developed. A mixture of either acetonitrile/water or acetonitrile/water/methanol was used as an extraction solvent mixture. After immunoaffinity column cleanup, the final extract was analyzed by high-performance liquid chromatography (HPLC) with a fluorometric detector (FLD). Mean recoveries from grapes, grape pomace, and lees samples spiked in the range of 1-200 microg/kg were 78, 86, and 88%, respectively, with a detection limit of 0.1 microg/kg and within-laboratory repeatability ranging from 6 to 15%. Tested on naturally contaminated samples of grapes, grape pomace, and sultanas, the method showed better performances as compared to two other methods also based on immunoaffinity cleanup and HPLC/FLD determination. Ochratoxin A was detected in samples of grape pomace (levels ranging from 34.2 to 456.8 microg/kg) and lees (levels ranging from 48.3 to 602.5 microg/kg) derived from the wine making of red grapes of 2004 and 2005 vintages in southern Italy. After distillation of contaminated grape pomace in a pilot-scale equipment to produce grappa, the toxin remained unchanged in the exhausted pomace and was not detected in any of the distilled fractions (detection limit of 0.02 microg/L).