Determination of multi-mycotoxins in cereals and of total fumonisins in maize products using isotope labeled internal standard and liquid chromatography/tandem mass spectrometry with positive ionization

Abstract

Mycotoxins are secondary fungi metabolites present in foods that cause adverse effects in humans and animals. The aims of this work were to develop and validate a multi-mycotoxin method to determine the presence of aflatoxins, citreoviridin, deoxynivalenol, fumonisins ochratoxin A, zearalenone and some metabolites/derivatives in rice, maize-based products and wheat-based products, and a method to determine total fumonisins (free and bound/hidden forms) in maize-based products. The validated multi-mycotoxin method was based on extraction with acidified acetonitrile and LC-ESI⁺-MS/MS analysis, with LOQs ranging from 0.5 to 121μg/kg, and proved to be suitable for the multi-mycotoxin analysis in wheat, maize and rice products. Bound/hidden fumonisins were determined after extraction of the free forms using the multi-mycotoxin method, followed by a basic hydrolysis of the unextracted bound/hidden and solid-liquid extraction with low temperature purification (SLE-LTP). The hydrolysis efficiency of the bound/hidden extraction procedure was investigated by analyzing a maize reference material and showed recoveries ranging from 75% (HFB2) to 108% (HFB1). The use of isotope internal standards was crucial for mycotoxins quantification in maize meal and wheat flour, while for rice, external calibration and matrix matched curves gave satisfactory results. All 55 samples of wheat-based products analyzed were contaminated with at least one mycotoxin and 16% of 44 rice samples were also contaminated. The most prevalent mycotoxins were DON and ZON in wheat-based products.

Keywords: Bound fumonisins; Cereals; Isotope internal standard; LC–MS/MS; Mycotoxins.