The Nose Is Good, but The Sensor Is Better, Or Chemists From Voronezh Are On Guard Of Health

Sensitive and durable sensors for determination of hydrogen sulfide concentration in the air were developed by chemists of the Voronezh State Technological Academy in collaboration with their colleagues from the Smolensk production association “Analitpribor”. Based on commercially available piesoelectric resonators, these sensors will reliably protect workers’ health by letting know that the poison concentration in the air has approached a dangerous boundary.

At first sight it seems that nature has provided for protection from the harmful gas. A human nose is able to catche hydrogen sulphide (according to the manual’s definition, the substance that strongly reeks) in absolutely tiny quantities when the gas concentration in the air is expressed in the thousandths of milligram per cubic meter. But the paradox is that this particular sensitivity of the nose can let us down: when the hydrogen sulphide concentration is approaching the maximum allowable value impending chronic desease of respiratory tract, blood, eyes, skin and digestive apparatus, the smell seems weaker to us. This is a kind of olfactory illusion.

The device developed by the Voronezh chemists will help to fight this illusion. It should be noted that researchers from the group under the guidance of Professor Yakov Kornman have learned to produce quite a variety of sensors based on microweighing of the air mixture analyte. They are based on the so-called piesoelectric resonators. These are devices the main component of which is a quartz plate covered by a special layer, vibrating at a strictly determined frequency under the influence of imressed voltage.

If we manage to find such a materiel for this covering that could efficiently and, most importantly, selectively sorb (extract and retain) molecules of a certain substance from the air, then a peculiar scales is obtained. The covering grows heavier due to analyte molecules “caught” from the air and begins to vibrate at a new frequency, the value of which depends on the quantity of analyzable compound accumulated in the coating material.
The task has to be solved anew for each new substance – the material should be found to selectively and efficiently extract a certain substance from the mixed gas. Every time the problem is successfully solved by the group under the guidance of Ya. I. Korenman and his colleague, Doctor of Science (Chemistry) Tatiana Kuchmenko. The problem was solved for hydrogen sulphide by development of an appropriate sensitive and selective sensor.

It is interesting to note that as a receptor covering – the layer on the surface of the quartz plate – the authors used various materials, including beeswax, which showed pretty good results. One of the best modifiers turned out to be the so-called apiezon wax – something like dense lubricant or resin. To make it adhere well to the quartz surface, the researchers suggest that it should be preliminarily processed by the polystyrene or starch solution.

Produced in strict compliance with such method, the sensors will be able to determine the hydrogen sulphide content in the air for 80 thousand times. Then the sensors can be replaced, and the old ones can be simply thrown away – this is an expandable and relatively low-cost material. The concept, its scientific and practical development is expensive. All that has been already done by the chemists. Now the production is pending – and them automatic devices will be constantly supervising the hydrogen sulphide concentration in workrooms, thus protecting the health of workers for whom, as Ford rightly remarked, no spare parts were provided for by nature.