New mass spectrometry method could diagnose patient's health from breath

Swiss scientists have developed a rapid method of analysing breath to reveal our body’s biochemical processes. The technique, which uses commercially available equipment, might be used in the clinic to diagnose a patient’s health. 

Renato Zenobi and his colleagues from the Swiss Federal Institute of Technology, Zurich, have found a way to rapidly detect the heavier, non-volatile compounds present in our breath, which are signatures of our body’s metabolism. Before now, Zenobi explains, only relatively light vaporous compounds had ever been collected. ’But breath is not really a gas - it’s like an aerosol, with tiny droplets,’ he said. Dissolved in those droplets are heavier molecules, like sugars or ureas: our body’s metabolic products. 

The researchers used extractive electrospray ionisation (EESI) mass spectrometry to detect a wide range of breath compounds. The method uses a relatively cheap, commercially available mass spectrometer. 

Within a second of a patient breathing into the device, their ’breath fingerprint’ appears on a computer screen. This avoids the tedium of complicated sample collection and pre-treatment processes employed by competing techniques, Zenobi claims. 

To illustrate their technique, Zenobi’s team investigated the effect of drinking beer, smoking cigarettes, and eating garlic on metabolism. Their preliminary results showed it was possible to detect the body’s biochemical processes changing in real time: after smoking, for example, the conversion of nicotine to cotinine provided a biomarker that could be followed in the breath fingerprint. 

’The potential for obtaining biologically significant information from the involatiles in breath opens a significant new area of analytical chemistry,’ commented Graham Cooks, who works in mass spectrometry at Purdue University, Indiana, US. The mass spectrometry method, he said, was an elegant variant on desorption electrospray ionisation (DESI), a way of ionising bulk solid or liquid samples without preparation. 

The researchers were also able to selectively detect the sulphurous compounds released by garlic, using silver cations to help the molecules to ionise. In the long term, Zenobi said, breath analysis could be used for clinical diagnosis, or as a base for biomarker research. But the method could also be applied to study other aerosol-like vapours: to detect the ripening of fruit, for example, by analysing the air around the food. 

Richard Van Noorden