Results of a Proficiency Test for multi-mycotoxin determination in maize by using methods based on LC-MS/(MS)

Introduction LC-MS/(MS) is routinely used for the simultaneous determination of mycotoxins in food and feed although official methods using this technique have not yet been adopted by CEN and AOAC International. Objective Conduct a proficiency test (PT) for the simultaneous determination of up to 11 mycotoxins [aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), ochratoxin A (OTA), deoxynivalenol (DON), T-2 toxin (T-2), HT-2 toxin (HT-2), zearalenone (ZEA), fumonisin B1 (FB1) and fumonisin B2 (FB2)] in maize using LC-MS/(MS) to benchmark laboratories currently using this technique and to obtain information on currently used methodologies and method-related performances. Methods Each participant received the following: instructions; a comprehensive questionnaire; a mixed mycotoxins calibration solution; a spiking solution (AFB1, AFB2, AFG1 and AFG2, OTA, DON, T-2, HT-2, ZEA, FB1 and FB2); two test materials, namely a contaminated maize sample and a blank maize sample to be spiked with a spiking solution containing 11 mycotoxins. Laboratory results were rated with z-scores. Results Of the 64 laboratories enrolled in the PT, 41 laboratories from 14 countries returned 43 sets of results for various combinations of analytes. The majority of laboratories (61%) reported results for all 11 mycotoxins whereas the remaining laboratories reported results for a restricted combination (from 2 to 10 analytes). For contaminated maize and spiked maize the percentage of satisfactory z-score values (|z| < 2) were: DON 55% and 49%, FB1 50% and 30%, FB2 52% and 38%, ZEA 68% and 64%, T-2+HT-2 toxins 82% and 85%, OTA 58% and 60%, AFB1 56% and 62%, AFG1 73% and 84%, AFB2 40% and 78%, AFG2 64% and 78%. The poorest performance (|z| > 3) was obtained for FB1 (31%), FB2 (32%), AFB1 (32%) and AFB2 (32%) in contaminated maize and for DON (35%), FB1 (63%) and FB2 (52%) in spiked maize. Mean recovery results were acceptable for all mycotoxins (74% to 109%), except for fumonisins, where these were unacceptably high (159% for FB1 and 163% for FB2). Conclusion A robust and reliable method for simultaneous determination of 11 mycotoxins in maize could not be identified from the results of this PT. Additional experimental work is necessary to set up a method suitable for interlaboratory validation. The results of this PT and the relevant method's details can be useful to identify methodology strengths and weaknesses.