A stable isotope dilution assay and liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of 12 mycotoxins in milk-based infant formula, milk, milk powder, and baby yogurt.
Despite the high initial instrumentation cost, with more [13C]-IS becoming commercially available and cost-effective sensitive LC-MS systems, stable isotope dilution will be used for routine mycotoxin analysis in the future, said the researchers.
The mycotoxins were aflatoxins B1, B2, G1, G2, and M1, deoxynivalenol, fumonisins B1, B2, and B3, ochratoxin A, T-2 toxin, and zearalenone, in milk-based infant formula and foods.
Webinar presentation
Dr Kai Zhang, lead author of the study and a chemist at US Food and Drug Administration (FDA) presented the findings during a webinar yesterday by AB SCIEX and Romar Labs.
He said there was ongoing LC-MS based mycotoxin analysis at FDA and the Center for Food Safety and Applied Nutrition (CFSAN).
Mycotoxins are toxic metabolites generated by fungi growing in foods and animal feeds.
US FDA Compliance Policy Guidance, sets the max detected concentrations of aflatoxin M1 in milk are >0.5 μg/kg (ppb).
The European Union (EU) maximum levels of aflatoxin M1 are 0.05 μg/kg in milk and 0.025 μg/kg in infant formula.
Methods used
Researchers used the LC-MS systems 4000 quadruple linear ion trap (QTrap) and 6500 QTrap from AB SCIEX and found for the 12 mycotoxins, the 6500 QTrap outperforms the 4000 QTrap with 3−50 times better sensitivity and 1−2 orders of magnitude more in linear dynamic range.
Samples were fortified with 12 13C uniformly labeled mycotoxins ([13C]-mycotoxins) that correspond to the 12 target mycotoxins and prepared by dilution and filtration, followed by LC-MS/MS analysis.
Average recoveries in fortified milk, milk-based infant formula, milk powder, and baby yogurt of range from 89 to 126% with relative standard derivations (RSDs) of <20%.
Individual recoveries in the four fortified matrices range from 72% (fumonisin B3, 20 μg/kg, milk-based infant formula) to 136% (T-2 toxin, 20 μg/kg, milk powder), with RSDs ranging from 2 to 25%.
The limits of quantitation (LOQs) were from 0.01 μg/kg (aflatoxin M1) to 2 (fumonisin B1) μg/kg.
In 60 samples, aflatoxins B1 and B2 were detected in one milk powder sample. Aflatoxin M1 was detected in three imported samples (condensed milk, milk-based infant formula, and table cream), ranging from 0.10 to 0.40 μg/kg.
The test portions were dissolved or diluted 10× times using acetonitrile/water (50:50 v/v) and then centrifuged and filtered through membranes with molecular weight cutoff at 3 kDa.
A stable isotope dilution assay was used to correct for the effects of suppression.
Source: Journal of Agricultural and Food Chemistry
Online ahead of print, DOI: 10.1021/jf4018838
“Determination of Mycotoxins in Milk-Based Products and Infant Formula Using Stable Isotope Dilution Assay and Liquid Chromatography Tandem Mass Spectrometry”
Authors: Kai Zhang, Jon W. Wong, Douglas G. Hayward, Marta Vaclavikova, Chia-Ding Liao, and Mary W. Trucksess