How to detect melamine in China food products

Melamine, a chemical normally used to make plastics and glues, is added to simulate acceptable protein levels. The chemical is at the centre of the latest tainted food scandal in China. Toxic ingredients from China killed or sickened thousands of dogs and cats in the US last year, prompting a public outcry. The WHO has said that as of Sept. 25, more than 54,000 infants and children in China had been taken to hospitals and clinics for treatment of urinary problems — such as renal tube blockages and kidney stones — related to the presence of melamine in infant formula and other dairy products. More than 14,000 infants had been hospitalized after ingesting the contaminated formula, of which a little less than 13,000 remained in hospitals. Some health experts said more must be done to ensure accuracy and overall food safety.

It is likely that the tainted milk was first diluted with water to increase its volume, and then had melamine added to boost nitrogen content, an indirect indicator of protein content. The chemical is not a substance used in any facet of food production.

People have to grind and homogenise the food samples, and then put them through a series of steps with an organic solvent to extract, clean and concentrate them before they analyse them for melamine.

GC-MS, LC-MS/MS & HPLC

The European Commission had recommended that all EU member states use gas chromatography-mass spectrometry (GC-MS) to analyze imports of wheat gluten and other raw materials from developing countries — in particular China. The US Food and Drug Administration (FDA) used the method to test for melamine and similar compounds in wheat gluten and pet food ingredients from China.

The samples are then separated into their parts using a process called Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS).

Mass spectrometry, which can detect very low evels of a compound, is then used to analyse them. LC-MS/MS testing is capable of detecting melamine levels as low as 0.05 parts per million (ppm). LC-MS/MS is a more precise instrument than GC-MS. This method would be used to test for melamine in the raw materials imported for use in creamers, milk powder and baby formula.

The technique is 500 times more sensitive in detecting melamine than high-performance liquid chromatography (HPLC), which was previously favored by the health department.

But the method to test for melamine in other, finished products remained unclear.