A COLLABORATIVE STUDY OF AN HPLC METHOD FOR DETERMINATION OF OCHRATOXIN-A IN WHEAT USING IMMUNOAFFINITY COLUMN CLEANUP

Thirteen laboratories within the United Kingdom participated in a coll aborative study to determine ochratoxin A in wheat using an HPLC metho d incorporating immunoaffinity column clean-up. Mean recovery of ochra toxin A from wheat spiked at a level of 5 mu g/kg was 91% for the meth od when using the OchraTest(TM) and 93% for the OCHRAPREP(R) brands of column. Four samples naturally contaminated with ochratoxin A consist ing of two blind duplicates containing concentrations of approximately 3 and 6 mu g/kg of ochratoxin A were examined using a specified metho d. The relative standard deviations obtained within laboratories (repe atability) ranged between 9.7 and 12.5%, there being no significant di fference between the two brands of immunoaffinity column. The relative standard deviations obtained between laboratories (reproducibility) w ere larger, ranging from 24.6 to 32.1% when wing the OchraTest(TM) col umn and 14.0 and 19.6% for the OCHRAPREP(R) column. Wizen results were corrected for recovery, the apparent difference in reproducibility be tween the two columns was much reduced, 14.0-17.3% for OchraTest(TM) a nd 10.4-17.5% for OCHRAPREP(R). Horrat values for reproducibility were between 0.4 and 0.7 before correcting results for recovery and were b etween 0.3 and 0.6 after correction. The performance of the immunoaffi nity column method tested compared very favourably with results of oth er published collaborative studies on mycotoxins.