Liquid chromatographic analysis of Alternaria toxins in carrots

A liquid chromatographic method for the analysis of Alternaria radicina and A. alternata toxins in carrots was developed. Toxins were extracted from carrot with an acidified mixture of water+methanol+acetonitrile. The filtered extract was divided in two parts that were purified by solid phase extraction on a C18 column for the analysis of radicinin (RAD), altertoxin-I (ATX-I), alternariol (AOH), and alternariol methyl ether (AME) and on a polymeric OasisÒ HLB column for tenuazonic acid (TeA), respectively. Toxins were quantified by reversed phase liquid chromatography with ultraviolet diode array detector by using two consecutive isocratic mixtures of acetonitrile-sodium dihydrogen phosphate solution. Mean recoveries of TeA, ATX-I, AME, RAD, and AOH from carrots spiked at levels between 0.5 and 3.0 µg/g were 69, 71, 90, 36, and 78%, with mean within laboratory repeatability of 14, 5, 4, 6, and 18%, respectively. The mean between laboratory reproducibility for the determination of TeA, ATX-I, AME, and RAD in spiked samples were 25, 22, 6, and 12%, respectively. Limits of detection (signal-to-noise ratio of 3) for RAD, TeA, ATX-I, AME, and AOH were 0.006, 0.02, 0.02, 0.01, and 0.005 µg/g, respectively. Radicinin was detected (0.16 – 13.9 µg/g) in 3 out of 266 carrot samples produced under organic conditions in three European locations, whereas A. alternata mycotoxins were not found in all tested samples.