Determination of ochratoxin A in beer.

Because of concern about possible transmission of ochratoxin A (OA) from contaminated grain adjuncts, development of a sensitive method for its determination in beer was investigated. Solid phase extraction (SPE) on C-18 and silica gel columns in series and on an immunoaffinity column (OchraTest) were used to obtain extracts for quantitation by reverse phase liquid chromatography with fluorescence detection. The standard curve was linear in the range 2.5-50 pg OA injected and detection limits for both methods were of the order 0.05-0.1 ng/ml beer (signal to noise 3:1). Per cent recovery of OA from various beer samples spiked at a level of 1 ng/ml averaged 82-100% for three modifications of the SPE method and 97% for the immunoaffinity column method. Forty-one samples of Canadian and imported beers were analysed. Trace levels of OA (< or = 0.2 ng/ml) were detected in 26 samples by SPE and/or immunoaffinity column methods; there was generally good agreement between the methods. Identity of OA was confirmed by methyl ester formation in five samples cleaned up by the immunoaffinity column procedure.