Improving the extraction efficiency on the determination of aflatoxin B1 and other mycotoxins in corn gluten feed - analysis by LC-ID-MS/MS.

Corn gluten feed (CGF) is a side-product from the manufacture of corn starch from maize grain by wet-milling. This process accumulates the mycotoxins in the CGF, moreover it gives an unique composition to CGF distinct from any other regular feed matrix for which mycotoxin analytical methods have been standardized. In this study, we report an optimised extraction medium for the determination of aflatoxin B1 (AFB1) and other mycotoxins in naturally contaminated CGF samples. Central composite experimental designs (CCDs) were utilised to find the appropriate extraction solution composition for the analysis of mycotoxins, which were quantified by liquid chromatography isotope dilution tandem mass spectrometry (LC-ID-MS/MS). The results highlighted that the acetonitrile percentage (AcN%) in the extraction solvent has the highest impact on the recovery, while the formic acid content (FA%) and the solvent-to-sample ratio (SSR) are not significant for AFB1. However, the FA% and the SSR are significant factors if a methanolic extraction is employed. The application of immunoaffinity clean-up (IAC) using MeOH-based extraction without acidification for such a complex matrix can result half of the concentrations compared to the concentrations we detected with AcN-based extraction. Non-acidified methanolic extraction medium do not totally precipiate the matrix constituents that bind the natural mycotoxins in CGF samples hindering their extraction. Therefore, the CGF samples need dedicated extraction conditions other than any cereal-based samples. The ideal extraction medium for AFB1 utilizing the dilute-and-shoot approach is AcN/water/FA, 72/26.6/1.4 (v/v/v). For the optimal co-extraction of all mycotoxins, QuEChERS should be executed using 50% AcN as the extraction solution.