Fig. 1 The chemical structure of Melamine
Melamine is a triazine nitrogen-containing heterocyclic organic compound. It is often used in chemical production. It is the main raw material for the manufacture of melamine-formaldehyde resin. It can also be used as an organic element analysis reagent. The main raw materials for the production of melamine are dicyandiamide and urea. Melamine itself is of low toxicity, but when used with cyanuric acid, it will form insoluble melamine cyanurate, causing serious kidney stones. It has been reported that during the digestion process of the human body, especially under the action of gastric acid, melamine itself may be partially converted into cyanuric acid and crystallized with the unconverted part. In 2007, the US pet food melamine contamination incident caused a large number of poisoned pets to die due to renal failure. In 2008, the melamine contamination of dairy products in China caused baby deformities and urinary system diseases.
Melamine is a chemical raw material and is not allowed to be used in food processing or food additives. However, some unscrupulous merchants mix melamine into dairy products to increase the nitrogen content level during protein content testing. China's dairy industry has suffered heavy losses due to the detection of a large amount of excessive melamine in products represented by Sanlu milk powder. Studies have shown that long-term intake of melamine may cause damage to reproductive capacity, bladder or kidney stones, and bladder cancer. The Codex Alimentarius Commission stipulates that the content of melamine per kilogram of liquid milk shall not exceed 0.15 mg. The International Agency for Research on Cancer of the World Health Organization has listed melamine as a 2B carcinogen. Melamine contamination of food is a food safety issue of concern all over the world, and it is necessary to monitor it. As a fast and sensitive detection method, ELISA is one of the best methods for monitoring melamine in food.
Indirect competitive ELISA