Specialists of the Scientific Production Association “Khimavtomatika” (Moscow) have developed a series of devices to determine concentration of such hazardous substances as nitric oxides, ammonia, ozone, arsine and phosphine in the air. The device operation principle is based on the fact that interaction between ozone and some compounds is accompanied by release of light. The phenomenon itself is called chemiluminescence, and its utilization enables to create native gas-analytical devices.
The essence of the method is as follows. The reaction between molecules of ozone (ozone is the gas, which is felt in the air after a thunderstorm; in small quantities the gas produces a pleasant feeling of freshness, but it kills in large quantities) and nitric oxide resulted in formation of molecules of oxygen and nitrogen dioxide. The latter goes out of the reaction slightly “excited” – figuratively speaking, somewhat “overfilled with energy”. Transition to the usual, more stable condition is accompanied by light quantum radiation of a certain wave-length – a molecule as if “drops” redundant energy. Consequently, by measuring this irradiation, one can evaluate the quantity of gases involved in the reaction. In theory, everything seems simple.
In practice, as it often happens, it has turned out that theoretical calculations are not sufficient. Gases do not behave ‘ideally’ in life and the researchers had to carry out enormous work to discover the regularities unambiguously binding radiation intensity with concentration of definable substances. Along with that, the optimal device design and reaction conditions were found for each of toxicants. For example, when analyzing the gas mixture for ammonia content, ammonia was first oxidized to get nitric oxides, to determine the nitric oxide content and indirectly – to determine the ammonia concentration. If nitrogen dioxide is to be determined – it can be transferred (converted) into oxide to determine its concentration by reaction with ozone and then to calculate initial dioxide concentration. If it is necessary to determine ozone per se – nitric oxide can, vice versa, be used as a reagent. Such is a continuous chemical round of events. As for arsine č phosphine, such products, the formation of which was accompanied by luminescence occurred among products of interaction between these extremely toxic gases and ozone. As a matter of fact, luminescence is very brief, but it turned out sufficient for designing a sensitive gas-analyzer. However, extensive experimental work was needed to this end.
As a result, specialists of the Scientific Production Association “Khimavtomatika” managed to design gas analysis devices to determine a number of gases. The names of all devices sound romantic: nitric oxides, ammonia and ozone are determined by the devices called “Maple”, and the arsine and phosphine concentrations will be determined by the “Platan” devices. It should be noted that all these gas analysis devices belong to one of the first chemiluminescent devices designed in Russia. Their metrological characteristics do not yield to respective attributes of foreign analogues. As for ozone gas-analyzer, the authors even provided for the in-built generator of the main reagent – nitric oxide. So, one can do without the usual gas-cylinder with a compressed reagent gas to make the method even more convenient.
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