Melamine cyanurate explained

Melamine cyanurate, also known as melamine–cyanuric acid adduct or melamine–cyanuric acid complex, is a crystalline complex formed from a 1:1 mixture of melamine and cyanuric acid. The substance is not a salt despite its non-systematic name melamine cyanurate. The complex is held together by an extensive two-dimensional network of hydrogen bonds between the two compounds, reminiscent of the guanine–cytosine base pairs found in DNA.^[1] Melamine cyanurate forms spoke-like crystals from aqueous solutions ^[2] and has been implicated as a causative agent for toxicity seen in the Chinese protein export contamination and the 2007 pet food recall. This complex is cited as an example of supramolecular chemistry.^[3]

Uses

Melamine cyanurate is used as a flame retardant, most commonly in polybutylene terephthalate (PBT), polyamide 6 (nylon 6) and polyamide 6,6 (nylon 6:6).^[4] It is also used to fireproof in polyester fabrics.

Toxicity

It has been considered to be more toxic than either melamine or cyanuric acid alone.^[5]

in rats and mice (ingested):

• 4.1 g/kg – Melamine cyanurate
• 6.0 g/kg – Melamine
• 7.7 g/kg – Cyanuric acid

A toxicology study conducted after recent pet food recalls concluded that the combination of melamine and cyanuric acid in diet does lead to acute kidney injury in cats.^[6] A 2008 study produced similar experimental results in rats and characterized the melamine and cyanuric acid in contaminated pet food from the 2007 outbreak.^[7]

See also

• 1,3,5-Triazine
• Hydrogen bonding

Notes and References

1. Perdigão LM, Champness NR, Beton PH . 2006. Surface self-assembly of the cyanuric acid-melamine hydrogen bonded network. Chem. Commun.. 5. 538–540. 16432575. 10.1039/b514389f.
2. Lili He. Yang Liu. Mengshi Lin. Joseph Awika. David R Ledoux. Hao Li. Azlin Mustapha. 2008. A new approach to measure melamine, cyanuric acid, and melamine cyanurate using surface enhanced Raman spectroscopy coupled with gold nanosubstrates. Sens. & Instrumen. Food Qual.. 2. 66–71. 10.1007/s11694-008-9038-0. 93425738.
3. Book: Lehn, J. M. . Supramolecular Chemistry: Concepts and Perspectives . VCH . Weinheim . 1995 .
4. Gijsman . Pieter . Steenbakkers . Rieky . Fürst . Christian . Kersjes . Joyce . Differences in the flame retardant mechanism of melamine cyanurate in polyamide 6 and polyamide 66 . Polymer Degradation and Stability . 2002 . 78 . 2 . 219–224 . 10.1016/S0141-3910(02)00136-2.
5. A.A. Babayan, A.V.Aleksandryan, "Toxicological characteristics of melamine cyanurate, melamine and cyanuric acid", Zhurnal Eksperimental'noi i Klinicheskoi Meditsiny, Vol.25, 345-9 (1985). Original article in Russian.
6. Puschner et al. (November 2007). Assessment of melamine and cyanuric acid toxicity in cats. Journal of Veterinary Diagnostic Investigation. Retrieved on 2007-11-16.
7. Identification and characterization of toxicity of contaminants in pet food leading to an outbreak of renal toxicity in cats and dogs.. Dobson. Toxicological Sciences. August 2008 . 106. 1. 251–62. 10.1093/toxsci/kfn160. 18689873. etal. free.