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Keen Sense Of Smell

31.10.2003


A unique device has been designed by the Moscow scientists – specialists of the Institute of General Physics, Russian Academy of Sciences, supported by funding from the Russian Foundation for Basic Research. The device not only helps to discover in a few seconds the minute quantities of narcotics and explosives in the air, but to identify and even count every single molecule of these dangerous substances. For the first time has the man managed to approach the creation of device more sensitive than the dog’s nose, besides, it is impossible to either divert or frighten or distract the device from trace.



As a matter of fact, all known methods – and there are several of them – either need preliminary division of air samples (that decreases significantly the sensitivity, and increases the duration of analysis and complicates the detection process) or determine the structure of a substance by its fragments. If the structure of a compound is complicated, and if this is not the sole substance in the sample (this is a common case), then instrumental inspection methods fail the fulfil the task. The task is beyond their “sense of smell”. That is why specially trained dogs have to be involved as their sense of smell is several times more sensitive than that of a man (which is natural), and even of that of the most complicated devices. However, here occur other problems: for instance, a handful of pepper completely deprives a four-legged “smeller” of an opportunity to spot the required scent. Besides, the dog, like human beings, may be in low spirits, or may have blocked nose, the dog can be diverted or distracted from trace – the criminal world has invented a lot of means. Therefore, the device is needed – an unbiassed, reliable and at the same time highly sensitive and selective one. The Moscow researchers have managed to develop such a device.

The device is based on a completely new principle developed by the Institute of General Physics (Russian Academy of Sciences) jointly with the University of Montana, USA. The essence of the principle is as follows: molecules of the sought substances first “settle” – they are sorbed on a specially processed silicic surface and interact with it. Then the laser beam, figuratively speaking, knocks the molecules off the surface but in a slightly different form. They have become positive ions, which differ from the original molecules by one thing only – a hydrogen ion (proton) is either added to or removed from them.


Such ions are easy enough to analyze – with the help of the so-called time-of-flight mass-spectrometer. The ions are sped up in the mass-spectrometer, and their mass is determined by the time of flight towards the target – and they are respectively identified.

“I should note we are very lucky, says Sergey Nikiforov, Ph. D. (Physics and Mathematics), project manager. The most widespread narcotics and explosives, and the majority of poisonous substances are nitrogen-containing compounds, possessing one property in common – the ability to participate in the proton exchange reactions (metathesis). Thanks to that, these substances can be analyzed with the help of our method – to be sorbed on silicon and to be protonated (or deprotonated) by the laser beam. There is no complete understanding of the ionization process on the rough surface yet and we are carrying out intense basic research supported by the Russian Foundation for Basic Research. Nevertheless, we have managed to utilize the fact, practically the gift of fortune or nature.”

Preliminary, the developers had to solve two complicated tasks. Firstly, to secure that the majority of the sought molecules “get stuck” to the sorbent – i.e., silicon wafer. To this end, the researchers made the silicon wafer rough, having significantly increased thereby the surface area of silicon.

Seconly, the standard sample was required. It was needed to create extremely low concentrations of the sough substances or their analogues, strictly quantitatively – in minor amounts of molecules. It is impossible to achieve that by simple dilution – this is too inaccurate. The method offered by the developers is exceptionally witty. The researchers have applied a well-known principle – the so-called piezosensitive element. This is a quartz plate, but with a preliminary covering, the weight of which can be measured by the oscillation frequency of the plate. The scientists suggested that the standard sample substance should be introduced into this covering like in the matrix. The substance gets evaporated in the vacuum chamber, and the difference of weight – and accordingly, the quantity of the substance, which got into the bulk of the chamber, - can be precisely measured by the oscillation frequency of this piezoelement.

As a result, the scientists have succeeded not only in developing a fundamentally new method, which allows to detect (as well as dogs do) the explosives and narcotics by minute (track) quantities of their vapor in the air. The researchers have also managed to produce and standardize the first pre-production model of such analyzer. Now they need to optimize its parameters and to develop the software so that the device could operate automatically. According to the inventors, this can be done within a year subject to sufficient funding of the project.

Sergey Komarov | alfa

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