Detecting homemade peroxide explosives could become easier, according to US scientists who have developed an electrochemical sensing method.

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Peroxide-based explosives are easy to make from readily available starting materials, and have been used by terrorist groups, such as in the Madrid train bombings of March, 2004. However, their lack of metal atoms or a nitro group makes them challenging to detect.

Joseph Wang and his colleagues at the Arizona State University, Phoenix, have developed a method to detect these explosives using an electrode coated with Prussian blue, iron hexacyanoferrate. This selectively electrocatalyses the reduction of hydrogen peroxide, which forms when a sample containing peroxide-based explosives is irradiated. This can be detected as a change in current in the system. The method is very sensitive, and can detect nanomolar levels of peroxide explosives.

Jehuda Yinon, an expert in the detection of explosives, formerly of the Weizmann Institute of Science, Israel, said, 'The electrochemical assay described for trace screening shows great promise as a rapid field sensing device. If indeed this could be developed into disposable microsensors for single-use application, as suggested by Wang and his colleagues, it would mean a significant breakthrough in counter-terrorist explosives monitoring.'

'This route offers great promise for meeting the sensitivity, selectivity, portability, speed, cost and low-power demands of field detection,' Wang said. He now intends to design a miniaturized detection system and develop disposable sensor strips.

Susan Batten