A direct method for analysing complex samples, such as urine or milk, has been developed by researchers in the US.  

Graham Cooks' team at Purdue University conceived a sample introduction method for spectroscopic analysis that would avoid time consuming sample preparation.

Cooks' method collides a spray of sample with a spray of solvent under ambient conditions.  The colliding microdroplets react and any compounds of interest can be fed directly into the mass spectrometer for analysis.

This avoids a drawback of conventional mass spectrometry: the pre-analysis steps for samples like urine, milk and polluted water. Usually these mixtures will undergo several 'clean-up' steps, to dilute down and remove excess salts that tend to interfere with the technique.  

Cooks hopes that this technology will be used to analyse a variety of problematic samples. 'Screening of urine for metabolic abnormalities, for pharmacokinetics studies, and in drug development research is likely to become much faster as a result of this technology,' said Cooks. 'Applications to environmental sampling are also facilitated by the lack of sample preparation and the very high sensitivity of the method.'  

This would result in shorter times and lower costs, and would also enable a high through-put of samples.  In addition, the solvent can be customised to the sample being analysed, making the technique very versatile.  

'I have no doubt that this will become a widely used technique for which the community of analytical chemists will be grateful,' said John Fenn, who won the Nobel prize for chemistry in 2002 for the development of soft desorption ionisation methods for mass spectrometry, of Virginia Commonwealth University, Richmond, US.

Michele R Zgraggen