Multimycotoxin detection and clean-up method for aflatoxins, ochratoxin and zearalenone in animal feed ingredients using high-performance liquid chromatography and gel permeation chromatography

The evolution of multiplex detection of mycotoxins using immunoassay platform technologies

Mycotoxins present serious threats not only for public health, but also for the economy and environment. The problems become more complex and serious due to co-contamination of multiple hazardous mycotoxins in commodities and environment. To mitigate against this issue, accurate, affordable, and rapid multiplex detection methods are required. This review presents an overview of emerging rapid immuno-based multiplex methods capable of detecting mycotoxins present in agricultural products and feed ingredients published within the past five years. The scientific principles, advantages, disadvantages, and assay performance of these rapid multiplex immunoassays, including lateral flow, fluorescence polarization, chemiluminescence, surface plasmon resonance, surface enhanced Raman scattering, electrochemical sensor, and nanoarray are discussed. From the recent literature landscape, it is predicted that the future trend of the detection methods for multiple mycotoxins will rely on the advance of various sensor technologies, a variety of enhancing and reporting signals based on nanomaterials, rapid and effective sample preparation, and capacity for quantitative analysis.

Aptamer-functionalized chitosan magnetic nanoparticles as a novel adsorbent for selective extraction of ochratoxin A

The preparation and application of aptamer-functionalized chitosan magnetic nanoparticles (Fe₃O₄@CTS@Apt nanoparticles) for selective extraction and determination ochratoxin A (OTA) were described in this study. Magnetic nanoparticle was synthesized by the coprecipitation method followed by coating with chitosan to improve its stability and biocompatibility. Further characterization was performed by scan electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and magnetic property measurement, and the results clearly indicated that the obtained magnetic chitosan nanoparticle was composed of magnetic core and chitosan coating layer. Aptamers specific to OTA were coupled onto the magnetic chitosan nanoparticles, and an extraction procedure was developed by optimization. When challenged with food samples fortified with OTA at 5 and 10 μg/kg, recoveries ranging from 91.3% to 99.1% with relative standard deviation (RSD) ≤ 4.2% were achieved by aptamer-functionalized magnetic extraction, which is very close to the results obtained by immunoaffinity chromatography extraction, indicating that this magnetic adsorbent could be hopefully used to achieve a fast and efficient extraction and detection of OTA in food samples.

Multiclass mycotoxin analysis in food, environmental and biological matrices with chromatography/mass spectrometry

Mold metabolites that can elicit deleterious effects on other organisms are classified as mycotoxins. Human exposure to mycotoxins occurs mostly through the intake of contaminated agricultural products or residues due to carry over or metabolite products in foods of animal origin such as milk and eggs, but can also occur by dermal contact and inhalation. Mycotoxins contained in moldy foods, but also in damp interiors, can cause diseases in humans and animals. Nephropathy, various types of cancer, alimentary toxic aleukia, hepatic diseases, various hemorrhagic syndromes, and immune and neurological disorders are the most common diseases that can be related to mycotoxicosis. The absence or presence of mold infestation and its propagation are seldom correlated with mycotoxin presence. Mycotoxins must be determined directly, and suitable analytical methods are necessary. Hundreds of mycotoxins have been recognized, but only for a few of them, and in a restricted number of utilities, a maximum acceptable level has been regulated by law. However, mycotoxins seldom develop alone; more often various types and/or classes form in the same substrate. The co-occurrence might render the individual mycotoxin tolerance dose irrelevant, and therefore the mere presence of multiple mycotoxins should be considered a risk factor. The advantage of chromatography/mass spectrometry (MS) is that many compounds can be determined and confirmed in one analysis. This review illustrates the state-of-the-art of mycotoxin MS-based analytical methods for multiclass, multianalyte determination in all the matrices in which they appear. A chapter is devoted to the history of the long-standing coexistence and interaction among humans, domestic animals and mycotoxicosis, and the history of the discovery of mycotoxins. Quality assurance, although this topic relates to analytical chemistry in general, has been also examined for mycotoxin analysis as a preliminary to the systematic literature excursus. Sample handling is a crucial step to devise a multiclass analytical method; so when possible, it has been treated separately for a better comparison before tackling the instrumental part of the whole analytical method. This structure has resulted sometimes in unavoidable redundancies, because it was also important to underline the interconnection. Most reviews do not deal with all the possible mycotoxin sources, including the environmental ones. The focus of this review is the analytical methods based on MS for multimycotoxin class determination. Because the final purpose to devise multimycotoxin analysis should be the assessment of the danger to health of exposition to multitoxicants of natural origin (and possibly also the interaction with anthropogenic contaminants), therefore also the analytical methods for environmental relevant mycotoxins have been thoroughly reviewed. Finally, because the best way to shed light on actual risk assessment could be the individuation of exposure biomarkers, the review covers also the scarce literature on biological fluids.

Methods of analysis for ochratoxin A

The mycotoxin ochratoxin A (OTA) is produced by the fungi Aspergillus alutaceus and Penicillium verrucosum and has carcinogenic, nephrotoxic, teratogenic and immunosuppressive properties. The levels of OTA in foodstuffs are regulated in several countries, so reliable and sensitive methods are necessary for its determination. Procedures for extraction of OTA from ground foods generally use an organic solvent in the presence of acid or an extraction solvent containing aqueous sodium bicarbonate. Cleanup procedures include partition into aqueous sodium bicarbonate, solid phase extraction (SPE) columns and immunoaffinity chromatography. The latter technique allows detection of sub-ppb levels of OTA in a wide variety of foods and in plasma. The most widely used determinative procedure is reversed phase liquid chromatography (LC) with detection by fluorescence (excitation 330-340 nm, emission 460-470 nm) or, more recently, by tandem mass spectrometry. ELISA methods are also available. Certified reference materials containing OTA have been prepared.

Effects of processing on zearalenone

Zearalenone (ZEN), a common contaminant of all major cereal grains worldwide, is produced by some plant pathogenic molds including Fusarium graminearum and F. culmorum. The biological activity of this mycotoxin is mainly attributed to its estrogenic activity that modulates/disrupts endocrine function in animals and possibly humans. Efforts have been made to reduce the level of ZEN by various chemical, physical, and biological processing methods. Some chemical treatments were shown to be effective in reducing zearalenone content in artificially or naturally contaminated foods. During physical processing, the fate of ZEN depended on its distribution in the food matrix and its chemical properties such as heat stability and solubility. For example, wet milling of contaminated corn resulted in starch that was essentially toxin-free. In contrast, animal feed fractions such as bran and germ, by-products of the wet milling process, tended to concentrate ZEN. Extrusion cooking, a complex process where food is subjected to heat, high pressures and shear stress, reduced ZEN levels in food as well as its estrogenic activity. Fermentation of foods with bacteria and yeast resulted in reduction in ZEN levels. However, fermentation can result in the conversion of ZEN to more potent derivatives such as cc-zearalenol. Further efforts are needed to identify effective methods for removing/detoxifying ZEN in foods.

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A method for the combined determination of the mycotoxins aflatoxin B1, G1, B2, G2, ochratoxin A and zearalenone in cereals and feed is described. After extraction with acetonitrile/water or methanol/water the cleaning takes place with new combined immunoaffinity clean-up column "AflaOchraZea" by VICAM. When the mycotoxins are determined in different cereals with this new type of clean-up column low detection limits and high recovery rates can be reached similar to those obtained by using separate immunoaffinity clean-up colums for the said mycotoxins.

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A method for the combined extraction of the mycotoxins aflatoxin B1, B2, G1, G2, ochratoxin A (OTA) und zearalenone (ZEA) in cereals is described. After extraction with acetonitril/water a clean-up for the mycotoxins was made using solid-phase columns (SiOH) or a combination of two immunoaffinity columns (aflaochra- and zearala-test-column from Vicam). The aflatoxins, ochratoxin A and zearalenone were detected after pre-column derivatization with trifluoroacetic acid in one HPLC run. The clean-up using two combined immunoaffinity columns is suitable because the detection and determination limits are low.

Determination of zearalenone in grains by high-performance liquid chromatography-tandem mass spectrometry after solid-phase extraction with RP-18 columns or immunoaffinity columns

In this paper a robust, sensitive and selective LC-MS-MS method for the determination of zearalenone (ZON) in several cereals is described. Sample preparation was performed by extraction of the commodities with a mixture of acetonitrile and water followed by solid-phase extraction with RP-18 columns or immunoaffinity columns. The selective determination of ZON was achieved with an atmospheric pressure chemical ionization interface. Using the negative ion mode a detection limit of 0.5 microg/kg and a determination limit of 1 microg/kg grain was achieved, which is by a factor of 100 more sensitive than the positive ion mode. Zearalanone (ZAN), which does not occur in nature, was used as internal standard for quantification. A linear working range from 1.0 microg/kg to 1000 microg/kg could be achieved in grains with a standard deviation of 4% and recovery rates around 100%. All these results were independent from the grain matrices (maize, barley, oats, wheat) when ZAN was used as internal standard. Sample preparation with RP-18 and immunoaffinity materials gave comparable results. In addition, the method was successfully used for the investigation of naturally contaminated maize samples in the course of an interlaboratory comparison test.

Derivatization reactions for the determination of aflatoxins by liquid chromatography with fluorescence detection

Various derivatization methods for the fluorometric detection of aflatoxins after separation by HPLC are reviewed. In normal-phase chromatography the sensitivity for aflatoxins B1 and B2 was improved by using special mobile phases or a flow cell packed with silica-gel particles. In the nowadays more popular reversed-phase methods, the fluorescence intensity of B1 and G1 can be increased by precolumn derivatization with trifluoroacetic acid or by postcolumn derivatization with iodine or bromine. Optimum conditions for the reactions are discussed. In terms of sensitivity, the three derivatization schemes give similar results. The methods are compared with respect to experimental convenience, selectivity, reproducibility and suitability for automation.