A Dilute-and-Shoot UHPLC–MS/MS Isotope Dilution Method for Simultaneous Determination and Confirmation of 11 Mycotoxins in Dried Distiller’s Grains with Solubles

Abstract

Natural contamination with mycotoxins in dried distiller's grains with solubles (DDGS) as a mainstream animal feed ingredient poses a risk to animal health. A regulatory method was needed for the agency to simultaneously detect 11 mycotoxins of high regulatory priority in DDGS. A DDGS sample (10 g) was extracted twice with acetonitrile-water under mildly acidic condition. Two aliquots from the combined crude extract were taken and processed separately: (1) diluted 400-fold with solvent for analysis of deoxynivalenol and fumonisins B1 and B2; and (2) with the pH adjusted to 7.5, and then diluted 15.7-fold for analysis of aflatoxins B1, B2, G1, and G2, ochratoxin A, zearalenone, and T-2 and HT-2 toxins. Uniformly labeled 13C-isotopologues of these mycotoxins were added as internal standards to the diluted extracts for quantitative analysis by ultra-high-performance LC-tandem MS. The linear quantitation ranges (µg/kg) were: aflatoxins B1, B2, G1, and G2, 1.57-105; zearalenone, 16.3-1090; T-2 toxin, 3.14-208; HT-2 toxin, 48.2-3220; ochratoxin A, 0.47-31.4; deoxynivalenol, 240-16000; fumonisin B1 and B2, 320-21200. Accuracies for these analytes at each of three fortification levels ranged from 70.7 to 100%, with corresponding RSDs between 1.4 and 10.5%. True recoveries were all higher than 83%. This method was successfully validated to meet the agency's performance guidelines for regulatory methods. This method is easy, quick, and robust to simultaneously quantify and confirm the presence of 11 regulated mycotoxins in DDGS.