Mycotoxin analysis

The reliability of measurements plays a pivotal role in food and agricultural areas, particularly in the case of undesirable toxic compounds such as mycotoxins. Quality-control principles for mycotoxin analysis are common to other trace analyses, so good laboratory practices, such as EN 4500, represent the heart of quality assurance requirements. Harmonized Guidelines for Internal Quality Control in Analytical Chemistry Laboratories, published by IUPAC (23), also presents valuable guidelines for the determination of mycotoxins. 

The working group CEN TC 275/WG 5 searched for performance criteria to be used in mycotoxin analysis and came up with a document reporting the criteria for the selection of methods (26). The criteria deal with limits of detection, minimum performance characteristics, extraction solvents, and applicability. Criteria for analytical methods in mycotoxin analysis are also included in Directive 98/53/EC (18). 

Among the elements of quality control in mycotoxin analysis, proficiency tests, control materials (reference materials and certified reference materials), traceability in spiking, and recovery checks have been demonstrated to be particularly relevant. 

Analyzing control materials alongside the test samples greatly improves proficiency in mycotoxin analysis. Certified reference materials (CRMs) represent ideal control materials, due to their statement of uncertainty and traceability, and they should be routinely used as much as possible. Unfortunately, as outstanding as the improvements made in the last decade have been, even though the list of CRMs in the area of mycotoxins is rather long, it is still insufficient. A list of the available reference materials in the mycotoxins area is reported in Table 1 the issue has been reviewed by Boenke (27). 

An excellent review of methods in mycotoxin analysis was published by the FAO (29), and yearly updates on analytical methods are provided by the General Referee Report, Committee on Natural Toxins, published in the Journal of AO AC International. 

As far as the mycotoxin analysis based on HPLC techniques is concerned, most methods include the following steps. 

Determination. The last step in mycotoxin analysis includes an additional separation achieved by HPLC column, followed by detection and quantitative determination, performed on the basis of the physicochemical characteristics of the mycotoxin. 

Food and Agriculture Organization of the United Nations. Training in Mycotoxins Analysis. Manuals of food quality control, 1990. 

PM Scott, MW Trucksess. Application of immunoaffinity columns to mycotoxin analysis. J AOAC Int 80(5) 941-949, 1997. 

In many instances of mycotoxin analysis there is a great need for screening methods that can analyse large volumes of food and feed samples, most of which will be mycotoxin-free. It would also be extremely helpful if such methods could be used by relatively inexperienced operators and in situations where good laboratory facilities are not available (Table 11.5). 

With at least two different SRM-transitions available for the analysis of a compound, one transition can be used for quantification ( quantifier ) and the other one for result confirmation ( qualifier ). If the branching ratio of quantifier to qualifier is found outside pre-defined ranges of acceptance, it is typically tried to apply a reanalysis with a more extensive chromatographic separation in order to overcome co-elution of interfering compound and analyte. This quantifier-qualifier-principle is used extensively in GC-MS and is now often applied for quantitative LC-MS/MS application too—especially in legally strictly regulated environments as forensic toxicology or pesticide and mycotoxin analysis in feed and foodstuff [55], In contrast,... 

Chu FS Mycotoxin analysis in Jeon IJ, Ikins WG (eds) Analyzing Food for Nutrition Labeling and Hazardous Contaminants. New York, Dekker, 1995, pp 283-332. 

Chu, F. S. 1991. Immunoassays for trace chemical analysis Monitoring toxic chemicals in humans, food, and the environment. In "Current Immunochemical Methods for Mycotoxin Analysis" (M. Vanderlaan, L. H. Stanker, B. E. Watkins, and D. W. Roberts, eds.), pp. 140-157. American Chemical Society, Washington, DC. 

The fluorometric assay is an efficient quantitative method for mycotoxin analysis. To obtain accurate results it is very important to remove interferences before the... 

Rudolf K, Alexandra M (2007) Mycotoxin analysis state if the art and future trends. Anal Bioanal Chem 387 145-148... 

FAQ. FAQ Food and Nutrition Paper. (1990) Manuals offood quality control. 10. Training in mycotoxins analysis, 14, 1-113. 

Spanjer, M.C., Scholten, J.M., Kastrup, S., Jorissen, U., Schatzki, T.F. Toyofuku, N. (2006) Sample comminution for mycotoxin analysis dry milling or slurry mixing Food Addit. 

Uhlig S, Eriksen GS, Hofgaard IS, Krska R, Beltran E, Sulyok M. Faces of a changing climate semi-quantitative multi-mycotoxin analysis of grain grown in exceptional climatic conditions in Norway. Toxins 2013 5(10) 1682-97. 

Table 2. Initial and final results of fungi and yeast count and mycotoxin analysis after 90 days of storage - with and without preservative...

RychUk M, Asam S (2008) Stable Isotope Dilution Assay in Mycotoxin Analysis. Anal Bioanal Chem 390 617... 

Krska, R. MolineUi, A (2007), Mycotoxin analysis state-of-the art and the future trends. Analytical and Bwamdytical Chemistry, Vol. 387, No. 1,145-148, ISSN 1618-2650. 

The use of a mass spectrometer as a detector for LC analysis brings a number of benefits to mycotoxin analysis. There is no need for chromophores or fluorophores in the analytes so derivatization can be avoided. The chemical structure of the analytes can be confirmed from molecular mass and fragmentation information and the use of tandem MS (MS/MS) allows greater selectivity. Multiple reaction monitoring and selected ion monitoring modes mean that chromatographic separation of all analytes is not necessary, as differentiation is carried out by the different ion transitions measured, and many multiresidue mycotoxin LC-MS methods now exist. These data acquisition modes can also increase the sensitivity of the method as the background noise is often reduced. 

In the frame of mycotoxin analysis, it is worth remembering that immunoaffinity columns are used for enrichment of samples to be analyzed by solution chemistry or by liquid chromatography. The use of immunoaffinity in this case allows a one-step removal of possible interfering agents from the sample. 

Chu FS (1995) Mycotoxin analysis. In Analyzing Pood for nutrition Labeling and Hazardous Contaminants, pp. 283-331. New York Dekker. 

For GC the mycotoxins need to be sufficiently thermostable and volatile or be converted into volatile derivatives. The two most widely used detectors in mycotoxin analysis - flame ionization detectors (FIDs) and electron capture detectors (ECDs) - do not require that a compound show any fluorescence or UV absorption, and the group of mycotoxins for which GC was initially the most widely used was that of the trichothecenes. More recently another group of Fusarium mycotoxins, the fumonisins, which also lack the appropriate optical properties, have been analyzed successfully using GC. 

---