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New technology reveals unknown pollutants

Tomas Nikovini og Armin Wisthaler

From NILU’s Annual magazine: Senior scientist Armin Wisthaler and NILU’s new mass spectrometer can detect volatile contaminants at unprecedented speed including species that have never been detected before. It is now also possible to analyse for example organic pollutants in the atmosphere from an airplane at full speed, to study unknown chemical reactions in indoor air and to investigate a series of other dependencies of importance for environment and human health.

Tomas Nikovini og Armin Wisthaler
Armin Wisthaler (right) and Tomas Nikovini measure the exhaust from an ethanol bus using the PTR instrument. Photo: Lone Lohne, Aftenposten (Scanpix)

By Bjarne Røsjø

A traditional method for measuring air pollutants is to direct air through a filter or cartridge for several minutes or even hours and to later analyse in the laboratory what kind of compounds have been captured. But pollutants can vary on very short timescales (seconds) and traditional methods only give a single snap-shot from an extended period of time. Armin Wisthaler is one of Europe’s most experienced experts in using a new instrument called PTR-TOF-MS (Proton- Transfer-Reaction Time-of-Flight Mass Spectrometer), that is eliminating many of the old technologies’ weaknesses.

“The instrument can detect volatile organic compounds (VOC), both in indoor and outdoor air,” explains Armin Wisthaler. “In the past samples have been analysed offline in the laboratory, but this instrument analyses the air quality immediately. By this we can for example place the instrument on board of an airplane, analysing the air continuously from its start until landing, from ground level up to flight altitude,” explains Wisthaler.

Analysis as fast as lightning

In brief, the new instrument consists of a small reactor with negative pressure, which is continuously flushed with air to be analysed. In the reactor water vapour molecules that carry an extra proton (H3O+) react as fast as lightning with organic compounds. The organic compounds obtain a positive electric charge and can be analysed in a high resolution mass spectrometer, which gives immediate information about the atomic composition of the molecule.

“One of the advantages about this technology is that the analysis goes very fast while we are doing our field work. Another advantage is that we do not any longer need to treat the air samples before analysis. The new spectrometer has already detected many molecules that are usually so reactive that they are lost on filters or cartridges or during the traditional laboratory analysis. I believe that these compounds are very important, because due to their reactivity they may also cause a biologic response in humans, for example in the respiratory tract or the eyes. There is a theory that these compounds contribute to the increasing incidence of irritation symptoms, asthma and allergies in many parts of the world,” explains Wisthaler.

Required big environment

The PTR technology has been developed for air sampling at the University of Innsbruck in the 1990s where Wisthaler and a small group of physicists have been working for many years to further develop this technology so that it can also be used for atmospheric research. In November 2011 he came to NILU to fully exploit the potential of this technology in a big center for air research with colleagues that can stimulate each other and develop new ideas. “In Innsbruck we were a small and exotic group of scientists at an institute that was actually working with other things,” explains Wisthaler.

Indoor air environment is more important than you think

Armin Wisthaler is full of ideas of how the PTR-technology can be used for practical surveillance of the environment and for new research projects. “We can for example examine if there are any unknown compounds in the exhaust of busses driven by bioethanol. We can also analyse the air that you breathe in and out to find out what kind of organic molecules have been taken up from your body. I am in deed very much interested in looking closer at indoor air pollution, which is probably more important than many might think. We spend most of our time indoors and many common building materials release chemical compounds that we know only little about. In addition, many of these compounds undergo chemical transformations in the indoor environment – forming highly reactive species which we have overlooked in the past. If I turn on the instrument inside my office or at the lab, I can see immediately that the air contains at least 100 different substances we know nothing about. I believe it is very important to develop more knowledge about indoor air pollution,” declares Armin Wisthaler.