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

Abstract

Liquid chromatography coupled with single or tandem mass spectrometry (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 the European Committee for Standardization and the Association of Analytical Communities. A proficiency test (PT) was conducted 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. 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); and 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. 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%, respectively. 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). 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 inter-laboratory validation. The results of this PT and the relevant method's details can be useful to identify methodology strengths and weaknesses.