13C isotope-labeled Mycotoxin Standards for GC- and LC-MS-MS

By: Pat Myers, Reporter US Vol 28

Mycotoxins are a diverse group comprised of hundreds of secondary metabolic products of various fungal species. Many show at least some toxicity in one or more organisms. Several show marked toxicity in humans with the effects of high-level exposure including death, hepatic toxicity, renal toxicity, neurotoxicity, immunosupression, and cancer. The effects of long-term low-level exposure have not been studied well.

Contamination of the food supply with mycotoxins is increasingly prevalent. This is likely due to increasing environmental and economic stresses. Contamination with fungi can occur during growth, harvest, transportation, processing, or storage of the food product. Water stress (either too much, too little, or at the wrong time), temperature stress, or infestation with insects can all lead to fungal contamination. Improper storage and transportation conditions can also cause or exacerbate the problem.

Human exposure to mycotoxins can be either by direct consumption of contaminated food sources or indirectly by consumption of products from animals fed contaminated feed. Techniques to reduce mycotoxin concentration after contamination are expensive, unreliable and sometimes reversible. Prevention of contamination and removal of contaminated products from the food chain are the only viable means of eliminating human expose. Sensitive and accurate detection of very low levels of these compounds is critical to governmental efforts to eliminate contaminated food sources from the marketplace. Accredited local laboratories capable of running validated and certified analyses of mycotoxins are a necessary part of the regulatory system.

Figure 1.Fully 13C isotope-Labeled Mycotoxins

A common method used to ensure the traceability to SI units required for validation and certification is the use of a primary-ratio method of analysis. Double Isotope Dilution Mass Spectroscopy (dIDMS) is recognized by the Comité consultatif pour la quantité de matière (CCQM) of the Bureau International des Poids et Measures (BIPM) as a primary method of measurement.

Both fully 13C isotope-labeled analogs of the mycotoxins and corresponding natural composition standards are required for dIDMS. In dIDMS, the sample and the analytical standard are each spiked with the isotope-labeled analog. Either GC-MS-MS or LS-MS-MS is then used to determine isotope ratios in the sample and standard. The change in isotope ratios caused by the addition of a known amount of 13C isotope-labeled analyte analog is used to calculate the concentration of the analyte in the original sample. Additionally, because the 13C isotope-labeled analogs behave chemically identical to the natural composition analytes, variations in sample preparation have little impact on the uncertainty of the analyses.

Sigma-Aldrich now provides a full range of 13C isotopelabeled mycotoxin standards along with the required natural composition standards for use in dIDMS, the newest of which are listed below. Please visit sigma-aldrich.com/mycotoxins to view the entire line of mycotoxin standards.

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  1. Prichard, Elizabeth and Vicki Barwick. Quality Assurance in Analytical Chemistry. Cornwall: John Wiley & Sons, Ltd., 2007.
  2. Kaarls, Dr. R.. “ CCQM: Consultative Committee for Amount of Substance – Metrology in Chemistry “. Bureau International des Poids et Measures. 3/17/2010 <www.bipm.org >.
  3. Fernandes-Whaley, Maria. The role of organic chemical metrology in food safety for South Africa. Pretoria: National Metrology Institute of South Africa, 2009.

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