Quantification of the Mycotoxin Deoxynivalenol (DON) in Sorghum Using GC-MS and a Stable Isotope Dilution Assay (SIDA)

Abstract

Sorghum has gained popularity with consumers as a grain source with its gluten-free and high protein dietary characteristics. Acreage has increased recently, in part due to the demand for an alternative feed source for poultry and swine. New information is needed about the level of mycotoxin contamination in sorghum accessions, and accurate and affordable analytical methods need to be developed and tested to quantify mycotoxins in sorghum. A traditional method (solid-phase extraction chromatography with C18, followed by GC-MS) to quantify the mycotoxin deoxynivalenol (DON) produced inconsistent DON values following controlled spiking and recovery experiments with different sorghum accessions. Consequently, we incorporated a stable isotope (d₁-DON) as an internal standard into a traditional GC-MS method. This method, stable isotope dilution assay (SIDA), was used to accurately determine DON levels in 196 sorghum samples representing 98 different accessions. Of the 98 accessions tested (two samples per accession), 76 of the accessions had DON levels that were greater than the limit of detection for both methods (0.20 μg g⁻¹). For a USA regulatory threshold of 1 μg g⁻¹, about one third of all the accessions (26/76) had at least 20% more DON using the SIDA method. For a regulatory threshold of 5 μg g⁻¹, about 7% of all the accessions (5/76) had at least 20% more DON using the SIDA method. Using SIDA, the amount of DON in a sorghum sample can be accurately and reliably quantitated by basing calculations on the recovery of d₁-DON, and this method may have future applications for quantifying DON from samples with complex matrices.