How is melamine detected in milk powder?

Melamine is a nitrogen-rich industrial chemical that has no legitimate place in food products. It became a global food safety concern after incidents of deliberate adulteration in dairy products, where melamine was added to inflate apparent protein content in quality tests. Because standard protein assays measure total nitrogen rather than actual protein, melamine passed undetected until targeted testing was introduced.

Why detection is difficult

Milk powder is a complex matrix. It contains proteins such as casein that are themselves nitrogen-rich. Any detector that responds broadly to organic compounds will see a large signal from the milk matrix itself, making it hard to pick out melamine at low concentrations.

This is where detector choice matters.

How the TEA detects melamine

The Ellutia 200 Series GC paired with the 800 Series TEA in nitrogen mode provides selective detection of nitrogen-containing compounds. In nitrogen mode, the TEA converts all nitrogen in the sample (except molecular N₂) to nitric oxide, which is then detected by chemiluminescence.

The selectivity is greater than 10⁷ gN/gC, meaning the detector responds ten million times more strongly to nitrogen compounds than to carbon compounds. In practice, this means the proteins and fats in the milk matrix produce negligible signal. Melamine, with its high nitrogen content, stands out clearly.

This selectivity removes the need for extensive sample cleanup that would be required with a less selective detector, simplifying the method and reducing preparation time.

Is this the same TEA used for nitrosamine testing?

Yes. The same 800 Series TEA is used, but in a different operating mode. Nitrosamine testing uses nitroso/nitro mode, which responds specifically to N-NO and N-NO₂ bonds. Melamine detection uses nitrogen mode, which responds to all nitrogen-containing compounds. The mode is selected based on the analytical question.

Want to discuss melamine testing or other nitrogen compound detection? Get in touch with the team.