The system produces a unique graphical fingerprint of the drugs in the form of a Raman spectrum.
Raman spectroscopy is a technique whereby laser photons are fired at a material and are scattered by the molecules in the material. The molecules lose, or gain, energy during this process, and the amount of energy lost or gained characterises, extremely accurately, the chemicals in the material. Together with other signals, this can provide a molecular signature – or unique ‘fingerprint’ of the molecule.
The breakthrough made by the developers of the new system overcomes problems caused by materials such as brick dust or talcum powder that are commonly used as bulking agents for diluting the drugs.
“The bulking agents can block out the data from the drugs with what is effectively a huge ‘flash’ of light that overwhelms the peaks identifying the drugs. A bit like a photograph that has been over-exposed with too much light flooding into the camera”, explains Professor Ewen Smith from the University of Strathclyde.
The new laser system effectively uses an extremely fast camera shutter speed, which allows data from the drugs to be collected before the blinding ‘flash’ from the bulking agents overwhelms the data from the drugs.
“Other methods of reducing the ‘fluorescence’, as this blinding flash is called, have been used in the past, but our technique – called Kerr gate fluorescence rejection Raman spectroscopy – has been shown to be very effective for many reasons”, explains Professor Tony Parker from the Central Laser Facility at RAL. “Apart from being non-destructive and non-invasive, the spectra produced are clearer and easier to interpret.”
Professor Dick Lacey from the Home Office Scientific Development Branch explains that although the results from this early research are extremely encouraging, a system for use at the scene of crime isn’t available yet.
“The equipment on which we have been testing the new technique needs a laboratory-based spectrometer which requires high power lasers and is very expensive. However, as the technology advances we expect that smaller units that are simple to operate will become available.”