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Reliability of mycotoxin assays--an update
W Horwitz1, R Albert, S Nesheim
1U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Washington, DC 20204.
Journal of AOAC International
|May 1, 1993
Summary
Recalculated mycotoxin assay precision shows most methods meet Horwitz equation predictions. Concentration is the main factor influencing results, with a 5 µg/kg limit for aflatoxin B1 in solid foods.
Area of Science:
- Analytical Chemistry
- Food Safety
- Mycotoxin Analysis
Background:
- Method performance data for mycotoxin analysis published before 1991 were compiled.
- International Union of Pure and Applied Chemistry (IUPAC) protocol was used for recalculation.
- Focus on precision parameters, specifically relative standard deviations among laboratories (RSDR).
Purpose of the Study:
- To re-evaluate the precision of mycotoxin analytical methods on a uniform basis.
- To compare the performance of different analytical techniques (TLC, LC, ELISA).
- To assess the influence of concentration, matrix, and analyte on method precision.
Main Methods:
- Recalculation of precision parameters from 793 published collaborative studies.
- Application of the Horwitz equation (RSDR = 2(1-0.5log10C)) for prediction.
- Comparison of RSDR values against predicted values for various methods and matrices.
Main Results:
- Approximately 80% of assays met or exceeded the precision predicted by the Horwitz equation.
- Thin-layer chromatography (TLC) and liquid chromatography (LC) showed similar precision, while ELISA was poorer.
- Concentration was the primary determinant of RSDR, outweighing analyte, method, matrix, and study age.
Conclusions:
- A quantitative limit of 5 µg/kg (ppb) for single analytes like aflatoxin B1 in solid foods is suggested based on the Horwitz curve.
- Enforcement of limits requires careful consideration of producer and consumer tolerance ranges.
- Existing data do not support a 0.05 µg/kg aflatoxin M1 limit in milk for interlaboratory enforcement.