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Melamine

Determining melamine in foodstuffs and animal feed using GC-MS

Melamine

Melamine (2,4,6-triamino-1,3,5-triazin or cyanuric acid triamide), a white powerder that is extremely soluble in hot water, is used in industry in the manufacture of synthetic resin, cleaning materials (dirt erasers) as well as upholstery materials. In 2006, melamine was detected in Chinese wheat gluten. Feeding led to the death of domestic pets through kidney failure. In September 2008, melamine was detected in Chinese milk powder and Chinese baby food. Six babies died and 294,000 children became ill. In Europe, there were isolated melamine findings in sweets and pastries of east Asian origin.

When using current analysis methods, melamine additives can result in the protein content appearing higher, due to the high nitrogen content in the molecules. From a toxicological point of view, melamine can be problemactic, as it can lead to the formation of crystals in urine and the kidneys, which can lead to renal failure.

Detection principle

Melamine and its associated components cyanuric acid, ammeline and ammelide, which can also be detected using this method, are extracted from the sample material using a DEA (diethylamine)/water/acetonitrile mixture. After derivatisation with BSTFA (N,O-Bis(trimethylsilyl)trifluoroacetamide) / trimethylchlorsilane (1%) and separation using GC, the melamine content is determined on the basic of the fragment ions characteristic of electron impact ionisation (EI). As part of this process, ion traces are measured using SIM (selected ion monitoring), method 3. One ion trace serves for quantifying (quantifier). The other two are used for calculating the intensity ratios as well a comparison of the retention times, which identifies the substance being examined. Quantification takes place with an isotype-marked melamine, which was added to the sample material to be extracted before extraction began. Futhermore, the derivatisation stage is controlled via a substance added before derivatisation occurred.

Fig 1: Standard solution (content represents 10 mg/kg sample): Quantifier (ion 327) and two qualifiers (ions 342 and 343)

Fig 2: Positive milk powder sample (content approx 10 mg/kg): Quantifier (ion 327) and two qualifiers (ions 342 and 343)

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