New laser method helps detect hidden liquid explosives and disease

8 October 2007

A new and powerful technique that can detect hidden liquid explosives through common plastic containers and glass bottles has been demonstrated by scientists from the Rutherford Appleton Laboratory (RAL), in Oxfordshire, UK.

The technique, known as 'spatially offset Raman spectroscopy' (SORS) was originally developed for medical and pharmaceutical applications, but has now been demonstrated to work in security applications. The technique — which can be implemented using a hand-held ‘probe’ — produces chemical information on liquids contained in transparent and diffuse plastic containers, including those made from coloured materials.

In the Raman effect, laser light shone on tissue or a substance gives a spectral signature specific to each chemical present.

SORS enables safe, non-invasive analysis of human tissue in vivo or the analysis of chemicals at depths of several millimetres. This is at least an order of magnitude deeper than that possible with conventional Raman methods.

The technology also has potential applications in the detection of adulterated food products and beverages as well as in quality control in the food, pharmaceutical and chemical industries.

There is real concern about the use of liquid explosives by terrorists, which has led to the current restrictions in place at airports. Current methods for detecting potentially dangerous materials are time-consuming and not always practical. The difficulty in detecting these substances is also compounded by the wide variety of packaging used by air travellers in which these explosives can be readily concealed.

The new technique is reported in the September edition of Analytical Chemistry (1). "This work is a fine example of how fundamental scientific research can come up with solutions to practical problems that concern every one of us," says Professor Mike Dunne, the Director of the Central Laser Facility at the Rutherford Appleton Laboratory where the research has taken place.

Dr Pavel Matousek, the project team leader, commented, "As well as this exciting use in security, this technology is applicable to a wide range of problems. We are now planning to develop the technology commercially through a new spin-out company, LiteThru Ltd, which will address areas such as pharmaceutical manufacture, anti-counterfeiting and medical diagnosis as well".

1. C Eliasson, NA Macleod and P Matousek. Non-invasive Detection of Concealed Liquid Explosives using Raman Spectroscopy. Analytical Chemistry, September 2007.

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