Melamine Testing

In response to many complaints from pet owners that their cats and dogs were sickened or died as a result of eating certain pet foods, the Food and Drug Administration (FDA), pet food manufacturers, state and university labs began a search for the causative agent. The FDA reported the first observation of melamine (CAS 108-78-1) in wheat gluten, pet foods, and in the kidneys and urine from sickened pets. Later this finding was extended to other ingredients including rice protein and corn gluten products. The compounds of interest also were expanded to include cyanuric acid (CAS 108-80-5), ammelide (CAS 645-93-2) and ammeline (CAS 645-92-1). Recently food production animals (swine, poultry) have become involved as result of having been fed contaminated feeds.

All contaminated products found to date can be traced back to ingredients purchased from China. Based on the level of contamination in some of the ingredients one of the hypotheses suggest that the compounds may have been deliberately added to the ingredients in order to increase their apparent protein content. Melamine by itself appears to contain in excess of 400% crude protein when analyzed by the accepted methods for determination of crude protein in foods, feeds and their ingredients.

The toxicological aspects of the melamine contamination are still under investigation. Recent findings indicate that mixtures of melamine and cyanuric acid form crystals similar to those observed in the kidneys of sick animals.

Shortly after learning about the problem the pet food industry undertook the largest recall of pet food in US history. The FDA followed up by giving its inspectors the power to detain without inspection all vegetable protein imports from China for use as animal or human foods if they suspect the products might contain melamine. They also intensified a sampling/testing regiment covering plant protein products from China currently in the US and further manufactured products. In a recent notice, the FDA stated that it had collected about 750 samples of wheat gluten and products made with wheat gluten. Of these 330 tested positive for melamine or melamine-related compounds. Of the 85 samples of rice protein concentrate and products made with the ingredient, 27 tested positive.

Analytes

The following compounds are among those covered by the current FDA GC-MS method:

• Melamine
• Cyanuric Acid
• Ammeline
• Ammelide

Test Method

Eurofins uses the FDA method published 4/25/07 on web. It involves the following steps:

• Homogenization of the sample by fine grinding
• Sample weight 0.5 – 1.0 g
• Extraction with 20% Diethylamine
• Filtration, addition of internal standard
• Aliquot dried and derivatized with BSTFA / 1% TMCS
• Derivatives analyzed by GC-MS

Quality Assurance

• Method cross validated within multiple Eurofins laboratories worldwide
• Use of a methylated melamine compound as an internal standard
• Recovery of the internal standard is monitored
• Use of blanks, and spikes for each sample type within an analytical batch
• Continuing calibration verification every 15 samples

References

• FDA published method for Melamine and related analogs.