Food Safety: Melamine test looks promising.
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The chemists at ETH Zurich (Renato Zenobi, Huanwen Chen, and colleagues) have developed a new mass spectrometric analysis method with which polluted milk can be detected reliably within 30 seconds.
Here is what they say about the test’s advantages over what currently is done to test for melamine.
”Explaining the advantages, Zenobi says, “Using ultrasound-assisted EESI-MS, we can analyse milk directly without any sample preparation steps. The method is fast and very accurate, and needs no more than one drop of milk.” Previously, an analysis required between twenty and sixty minutes to determine the concentration of melamine in a milk sample using standard methods. Zenobi’s group can do it in just 30 seconds. The current publication describes the analysis of milk, milk powder and wheat gluten, but, according to Zenobi, EESI-MS can, in principle, be used to determine the level of melamine in any foodstuff. The detection limit is 500 ppb (parts per billion) – which is five times less than the limit value allowed in foods in the USA and EU.”
See Chemical Communications by R. Graham Cooks from Purdue University for another method of testing. This seems to be the test with the most promise in terms of ease and quickness. I'll try to cover the R. Graham Cooks test in a later post.
”Portable EESI-MS for on-site analyses
A comparable analysis method for melamine was published in the same issue of “Chemical Communications” by one of Zenobi’s colleagues - R. Graham Cooks from Purdue University, USA. However, Cooks atomises and ionises his milk sample by bombarding it with a charged gas (low-temperature plasma; LTP). Zenobi is happy to say that, “Both methods are accurate, fast and robust. Our results are practically identical; the fact that they now appear in the same journal is an amusing coincidence. I really knew nothing of Graham’s melamine project until a short time ago.” At present, the chemist is unwilling to speculate as to whether one of the methods will ultimately become established, and if so, which one. In principle, both methods can be used by any laboratory equipped with an electrospray MS without significant additional expense. Nevertheless, Zenobi is not overly confident that the methods will gain immediate acceptance in foodstuffs testing laboratories: “Established methods usually persist for a very long time – it is hard for innovations to gain a foothold.”
His group is currently working to develop the method further for use in the field. The scientists have in mind a portable instrument that could be used to measure the melamine content directly when the milk is being processed, for example during bottling. Explaining the essential advantage of such an analysis instrument, Zenobi says, “The shorter analysis time is one thing, but the majority of the time - and therefore money - is lost during all the logistics connected with taking the sample.” He is still to receive a direct enquiry from China regarding application of the technology. However, easy-to-handle analysis instruments based on EESI-MS technology might one day contribute to preventing a food scandal such as the one in China at an early stage.”
References
Zhu L, Gamez G, Chen H, Chingin K, Zenobi R. Rapid detection of melamine in untreated milk and wheat gluten by ultrasound-assisted extractive electrospray ionization mass spectrometry (EESI-MS). Chem. Commun. 2009; Advanced online publication doi:10.1039/b818541g
Huang G, Ouyang Z, Cooks RG.High-throughput trace melamine analysis in complex mixtures. Chem. Commun. doi:10.1039/b818059h