Survey of Canadian retail coffees for ochratoxin A.
One-hundred and one specimens of coffee were gathered from retail outlets across Canada and analysed for ochratoxin A. Seventy-one specimens were roasted beans or roasted ground coffee, and 30 were instant (or 'soluble') coffees.  All samples were extracted with methanol-sodium bicarbonate.  The extracts were cleaned up either by immunoaffinity column chromatography or by a combination of solid-phase extraction and immunoaffinity column chromatography.  Ochratoxin A was quantified by liquid chromatography (LC) with fluorescence detection.  The minimum quantifiable level was 0.1 ng g(-1).  Ochratoxin A was present, above the minimum quantifiable level, in 42 (59%) of 71 beans and ground coffee and in 20 (67%) of 30 instant coffees.  The mean ochratoxin A level in the positive samples of beans and ground coffee was 0.6 ng g(-1), and the mean level in the positive samples of instant coffee was 1.1 ng g(-1).