You may remember the melamine scandal where in September this year over a thousand babies were made ill and four died as a result of producers putting melamine, or worse, melamine scrap  into milk to increase its apparent protein content as determined by standard analytical methods (basically nitrogen determination.)

A couple of days ago I came across an online article: Dairy detection: monitoring melamine in milk from which it appears that two groups, one that of Renate Zenobi of ETH Zürich [1] (‘home’ of Einstein and many other famous physicists), and that of Graham R. Cooks at Purdue University, West Lafayette, USA, [2] have worked out “quick and easy” ways of getting milk samples into mass spectrometers to detect tiny concentrations of melamine.

However, I do not expect our readers to be contented with what is only a recycled press release of their two forthcoming papers, so I wanted to find out more about the techniques they used.  In particular, how could what I regard as a relatively bulky apparatus, namely a mass spectrometer, be used for such a rapid-response analytical technique?

Well, John H. Callahan, Ph.D. of the Center for Food Safety and Applied Nutrition, U. S. Food and Drug Administration is very helpful in allowing online the PowerPoint presentation of Emerging Approaches for Rapid Analysis in Food Safety Problems.  Indeed, this article starts with melamine, though related to the contaminated pet food that turned up in the USA in 2007.  Mass spectroscopy, one can see, has moved on from the standard GC (gas chromatography) / MS that our chemistry graduates work with.

The Lafayette group are fortunate in having a friendly local analytical instrument company, namely Griffin Analytical Technologies LLC, West Lafayette, Indiana, USA, who combine the newer types of sample ionization with Tandem mass spectrometry,  also known as MS/MS, which involves multiple steps of mass spectrometry selection, with some form of fragmentation occurring in between the stages.  As an example of what they can do, there is a paper [3] where  they show separation of Cinnamon, Spearmint, Peppermint and Wintergreen in  Altoids:  the Original Celebrated Curiously Strong Mints

But both in Zürich and Lafayette, the clever part is in generating two different but effective ways of getting the melamine into the mass spectrometer in the first place, avoiding extensive sample preparation and taking the milk almost straight from the milkmaid’s bucket, as it were.

[1] Rapid detection of melamine in untreated milk and wheat gluten by ultrasound-assisted extractive electrospray ionization mass spectrometry (EESI-MS) Liang Zhu, Gerardo Gamez, Huanwen Chen, Konstantin Chingin and Renato Zenobi, Chem. Commun., 2009 DOI: 10.1039/b818541g

[2] High-throughput trace melamine analysis in complex mixtures Guangming Huang, Zheng Ouyang and R. Graham Cooks, Chem. Commun., 2009 DOI: 10.1039/b818059h

[3] Implementation of DART and DESI Ionization on a Fieldable Mass Spectrometer  J. Mitchell Wells, Michael J. Roth, Adam D. Keil, John W. Grossenbacher, Dina R. Justes, Garth E. Patterson and Dennis J. Barket Jr  Journal of the American Society for Mass Spectrometry Volume 19, Issue 10, October 2008, Pages 1419-1424 doi:10.1016/j.jasms.2008.06.028