Less than a year ago this blog reported on the melamine milk scandal and why chemical testing apparently is not that straightforward. There obviously is room for improvement and the first innovation in melamine testing is just in (DOI).
Ai, Liu and Lu of the Chinese Academy of Science @ Changchun combine cyanuric acid with gold particles in colloidal gold via a ethylene mercapto spacer. The color of this water solution is wine-red but when melamine is added it turn blue. The melamine forms the well-known melamine cyanurate complex through extensive hydrogen bonding as a result of which the gold particles aggregate and it is well known that the color of colloidal gold solutions depend strongly on gold particle size.
The great news is that the researchers report melamine detection at the 2.5 ppb level and that within one minute which is three times below the melamine safety limit. Issue to solve: detection of melamine in raw milk at the 2 ppm level still requires extensive sample preparation (extraction, filtration, centrifuging) because many other milk components would otherwise interfere.