ETH Zürich: Instant analysis of chemicals on surfaces

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A group of researchers led by Renato Zenobi, Professor of Analytical Chemistry at the Organic Chemistry Laboratory of ETH Zürich, has developed an instant analysis technique based on quadruple time-of-flight (QTOF) mass spectrometry, for detecting chemicals on surfaces, including that of living organisms and skin.

The development represents a further advance on a method developed by the group in which the researchers used a similar approach to detect various substances in breath. Using the enhanced method, they claim they very precisely analyse substances on surfaces of any kind.

Both methods are based on standard QTOF mass spectrometry, where samples are normally presented in solution, which is then electro sprayed, with the additional aid of a desolation gas. The tiny droplets generate ions that are characteristic of the substances in the sample.

Instead of studying the substances in the solution, the ETH measured the substances present in the desolation gas. With the new method nitrogen is blown from a small nozzle onto a sample surface. As the gas strikes the surface it absorbs semi-volatile substances. The gas stream is then fed into the mass spectrometer where the absorbed substances are analysed.

Standard mass spectrometers can readily be modified to use the new technique. The new method increases the range of surfaces that can be analysed. “One particular strength of our approach is that even the surfaces of living organisms can be examined,” said Zenobi. It only takes a few seconds to measure a single sample, so large numbers of random samples can be routinely analysed.

For samples of meat the scientists were able to show that the sample material does not even need to be thawed, while traces of nicotine, coffee and explosives could be detected on skin.

According to Zenobi the great advantage is that the technique is fast and non-invasive, and needs no special sample preparation.