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Trace-Level Analysis of Melamine and Related Compounds by LC-MS/MS

Featured Application: Analysis of Melamine and Related Compounds on Raptor HILIC-Si

  • Improve productivity—analyze five potential food adulterants in just one injection.
  • Ensure accurate trace-level results with excellent sensitivity at 25 ppb.
  • Increase sample throughput with a fast, 3.5-minute separation.

Foods with a high protein content command a higher price on the market, which can result in the illegal practice of food adulteration using nitrogen-rich compounds to make the protein content appear higher than the actual value. The Kjeldahl and Dumas methods are often used to measure protein content, but both methods assess protein content indirectly by measuring nitrogen content. As long as protein content is not measured directly, food adulteration with nitrogen-rich compounds for economic gain may persist, and analytical methods to detect potential adulterants (nonprotein nitrogen sources) need to be kept current, as the chemical space for cheap nitrogen-rich compounds is vast.

Melamine is a nitrogen-rich compound that has been previously identified as a food adulterant in both pet food and infant formula. Melamine can also form in vivo as a metabolite of the insecticide cyromazine. The analysis of melamine and related compounds (cyanuric acid, ammelide, and ammeline) is required when exporting feed materials to the U.S. and EU due to concerns about potential toxicity. In addition, the FDA requires that at-risk pharmaceutical components (albumin, colloidal oatmeal, gelatin, lactose, etc.) be screened for melamine before they are released for use in manufacturing or preparation of drug products. The FDA has set the tolerable daily intake level at 0.2 mg/kg for adults with the additional requirement that a single food product may only contain a maximum concentration of 2.5 ppm (1 ppm for infant formula).

The LC-MS/MS method shown here allows the combined analysis of melamine and related compounds, which is much more efficient for labs screening for multiple potential adulterants. A Raptor HILIC-Si column was selected for this method because it provides good retention of these highly polar analytes that can be difficult to retain on other phases, allowing accurate identification and quantification. Using this method, labs can analyze melamine and related compounds at residual levels with a fast separation time of only 3.5 minutes and a complete cycle time of 8 minutes. This fast, multi-analyte method is recommended for high-throughput labs that need to test for multiple potential contaminants at trace levels with quick turnaround times.

PeakstR (min)Precursor IonProduct IonProduct IonPolarity
1.Cyanuric acid0.47127.884.942.1-
ColumnRaptor HILIC-Si (cat.# 9310A52)
Dimensions:50 mm x 2.1 mm ID
Particle Size:2.7 µm
Pore Size:90 Å
Temp.:30 °C
Diluent:5:95 Water:acetonitrile, 10 mM ammonium formate, 0.1% formic acid
Conc.:25 ng/mL
Inj. Vol.:5 µL
Mobile Phase
A:Water, 10 mM ammonium formate, 0.1% formic acid
B:5:95 Water:acetonitrile, 10 mM ammonium formate, 0.1% formic acid
Time (min)Flow (mL/min)%A%B
Ion Mode:ESI+/ESI-
Mode:Scheduled MRM