Industry Sectors Introduction
On March 16, 2007, the FDA announced a massive recall of pet food, affecting 95 brands of both dog and cat foods. The foods appeared to be causing renal failure in some animals, leading to at least 15 confirmed deaths. The recall has since expanded to cover over 100 brands of both dry and wet food, and the anecdotal death total is in the hundreds.
Initial reports from a New York laboratory indicated the presence of aminopterin, a rat poison and experimental cancer drug. Later reports from FDA could not confirm this finding, although they did announce that they had found melamine, an industrial chemical used in the production of plastics and fertilizers, among other things.
In response to the initial reports, we have developed methods to analyze pet foods for melamine and aminopterin.
The melamine method is based upon LC-MS/MS and is sensitive to approximately 0.5 ug/g. The aminopterin method is also based on LC-MS/MS, and is sensitive to approximately 0.05 ug/g. We have successfully used both of these methods to analyze both dog and cat foods.
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Melamine
Melamine may have been used to increase the apparent protein assay of wheat gluten, a food additive. If so, melamine would have been added at relatively high levels (%).
On April 5, 2007, the FDA reported that melamine was found in 21 out of 400 samples tested. The FDA also posted methods used in testing based upon GCMS of TMS derivatives (screening test, not quantitative) and an HPLC-UV test. Neither of these methods are considered both specific and quantitative for melamine in complex samples like pet food.
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Aminopterin
Aminopterin is a cancer drug and rodenticide (rat poison). It was the toxin initially suspected in the March 2007 recall of pet foods. Use as a rat poison is banned in the US but not in China. The suspected origin is wheat gluten, a food additive.
Testing for Melamine and Aminopterin
Pet food samples are extracted into water. These water extracts are filtered, then analyzed by LC-MS/MS without further treatment.
Ionization is accomplished using an electrospray interface. MS/MS is carried out in the positive ion mode, monitoring various transitions from the molecular ions.
LC-MS/MS Chromatograms:
Melamine
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Aminopterin
