Fourier transform mid-infrared spectroscopy with attenuated total reflection (FT-IR/ATR) as a tool for the detection of Fusarium fungi on maize

Abstract

The application of Fourier transform mid-infrared spectroscopy with attenuated total reflection (ATR) for the detection of Fusarium graminearum as an indicator for the presence of the mycotoxin deoxynivalenol (DON) is described. This rapid screening method for the determination of Fusarium fungi, which produces DON as its main metabolite, could speed up analysis time, resulting in a higher sample throughput, as conventional determination is a time-consuming and tedious task. In this study the fungus itself was determined on maize by pressing the ground sample against a diamond ATR-crystal with 3 internal reflections and recording the mid-infrared absorption spectrum. Reference measurements were performed by determining ergosterol with HPLC-DAD. Obtained concentrations of ergosterol served as a parameter for the total fungal biomass contained in the sample. DON was determined with GC-ECD after extraction with acetonitrile and clean-up with Mycosep™ columns. Principal component analysis (PCA) was used to separate contaminated maize from blank samples using the first derivative of spectra. Results showed that, for concentrations greater than 8.23 mg/kg ergosterol and 0.13 mg/kg DON at least 75% of samples were correctly classified. Exceptions are due to inhomogeneities in the sample, which will be dealt with in future studies. The PCA score plots for the first two principal components illustrate the feasibility of this approach as a separation between the two sample sets can be clearly seen. Concentrations of ergosterol and DON in tested samples ranged from 0.79–947 mg/kg (ergosterol) and from 0.13–2.59 mg/kg (DON). For PCA these samples were always compared with a blank.