Researchers in Japan and the United States have developed an inexpensive miniaturized sulfur dioxide (SO₂) analyzer that can run on a 12-volt automotive battery. The new device could help developing countries monitor atmospheric SO₂ levels and can be easily deployed in the field to monitor SO₂ emissions from natural sources like volcanoes.

Although anthropogenic emissions of SO₂ have been regulated for several decades, many developing countries cannot afford control technologies and still burn fossil fuels with high sulfur content. Natural emissions of SO₂ also contribute to high levels of the respiratory irritant in the atmosphere.

Commercially available SO₂ analyzers are typically bulky and require large volumes of solution to absorb the collected gas. Such devices can take up to one hour to accumulate the gas into solution, and they require AC power supplies, which are not easy to find in the field. To overcome these limitations, Kei Toda of Kumamoto University in Japan, and colleagues developed a smaller, less costly SO₂ analyzer that does not require an AC power supply.

In the new device, SO₂diffuses through a porous polypropylene membrane and absorbs into 800 nanoliters of a dilute sulfuric acid solution containing 2-propanol and hydrogen peroxide. SO₂ is oxidized to sulfuric acid, and the resulting change in conductivity is measured by microfabricated electrodes integrated into the gas collection device.

Under optimized conditions, the new SO₂ analyzer can detect as little as 0.7–1.0 parts per billion (by volume) in about 1.5 minutes. Compared with commercial SO₂ analyzers, the new device offers better temporal resolution and therefore much more accurately measures quickly changing atmospheric concentrations. The researchers believe that this general approach could be used to monitor numerous other air pollutants. (Anal. Chem. 2002, 74, 5890–5896)