Ochratoxin A in plasma of Norwegian swine determined by an HPLC column-switching method.

A method well suited for screening large numbers of plasma samples for ochratoxin A is presented. Proteins were precipitated with methanol and the supernatant diluted with 0.01 M phosphoric acid before 1 ml extract was injected into a high-performance liquid chromatograph (HPLC). The extract was further cleaned up and pre-concentrated on a polystyrene-divinylbenzene precolumn. After column-switching, the sample was chromatographed on a C18 analytical column, and ochratoxin A was detected with a fluorescence spectrophotometer, either directly or after postcolumn pH shift. The detection limit was 0.10 ng ochratoxin A/ml plasma. The method was used to determine the ochratoxin A concentration in 216 samples of swine plasma. They were collected from different herds in June 1991 from ten slaughterhouses, located in different parts of Norway. Eighty-two percent of the samples contained > or = 0.10 ng ochratoxin A/ml plasma while 0.9% contained > or = 5.0 ng/ml.