SU1758526A1 - Method of determination of content of components in liquid and gaseous media - Google Patents

Abstract

Usage: in warning devices for explosive vapor concentrations. SUMMARY OF THE INVENTION: Two elastic members with a specific surface area of 2–200 m / kg between each other are deformed by 10% between voltage sensors. The latter are included in the shoulders of the bridge circuit. The lengths of the elements are recorded and the presence of the analyte is determined by the difference in stresses in the deformed elements. 2 ill., 1 tab.

Description

The invention relates to methods for analyzing the atmosphere (gases) in order to detect vapors of organic liquids or to prevent explosions (fires) in mines, mine workings, chemical and oil refineries, and also to analyze the fuel for the presence of water or other liquids. The invention can be used in the production of simple indicators, alarms and analyzers designed for continuous or periodic monitoring of the composition of gas mixtures, atmosphere, water, fuel, etc.

There is a known method for the determination of vapors and gases, which includes passing the gas along the heat sinks of the heating element coated with a selective sorbent, and measuring the temperature of the element. During sorption of lars by the surface of the heating element, heat transfer decreases, and the vapor concentration is determined from the temperature of the heat sinks.

The method allows the indication of vapors of saturated hydrocarbons, gasoline, kerosene and other fuels and lubricants. However, it is energy intensive and complex.

The closest to the present invention is a method for determining water vapor, implemented in a film or hair hygrometer, the determination of water vapor content in gaseous media. This method is performed by measuring the deformation of an elastic element (human hair or hydrophilic membrane) under the simultaneous action of water vapor and mechanical tension Moreover, the mechanical stress is small, of secondary importance and necessary only for more accurate measurement of the length of flexible elements that change their shape (length) under the influence of water vapor dissolved in the hydrophilic material.

The disadvantage of this method is a limited range of substances (liquids), the vapors of which can be determined in the atmosphere. Only polar liquids causing swelling of the hair or hydrophilic membrane are subject to indications in a known manner. The sensitivity and selectivity of the method are small, and the determination or indication of fumes fuels is impossible.

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The purpose of the invention is to increase the sensitivity, speed and selectivity of the determination.

Delivered is achieved by the fact that according to the method of determining the content of components in liquid and gaseous media, which means that a sensitive element is placed in the analyzed medium, the change in its physicomechanical parameter, measured by the value of the analyzed component, is measured as the material a sensory body uses a polymer that is adsorbable to the component being analyzed; before measuring, the sensitive element is deformed and held in the absence of th component to a constant value of voltage, and as the measured parameter using voltage change in time.

The proposed method is based on the effect of accelerating the relaxation of stresses in elastic bodies under the action of surface-active and plasticizing agents in a liquid or gaseous state. In contrast to the known method, where a change in the length of an elastic element (hair) under constant voltage is measured, a decrease in stress in a element with a fixed length (deformation) is to be measured. The stress in an elastic element decreases faster under the action of surfactants than the length of a hair changes under the action of water. This is due to the increase in display speed. The surfactant effect of the substances on the elastic element is more selective than plasticizers, and this achieves the effect of increasing the selectivity of the proposed method. The condition for the predominance of the surface mechanism of voltage reduction in the elements is their high specific surface area.

FIG. Figure 1 shows a scheme for fixing and deforming a sensitive element between voltage sensors (strain gauges of the GDT type); in fig. Figure 2 shows the inclusion of mechanical voltage sensors in a bridge circuit.

FIG. 1 and 2 shows sensors 1-4. DC source 5 (voltage), DC amplifier 6 and actuation device 7.

Example 1. Gasoline B-70 vapor was measured in the air. A film of a trifluorochloroethylene and vinylidene fluoride copolymer (fluoronone F-3M) is chosen as the material of the sensitive element. Deformed two strips of the film forflon F-ZMS (5)

(10,100-0.1 mm) by 3% between strain gauges of type DGT included in the shoulders of the bridge circuit (Fig. 1). Withstand film sensitive elements under

voltage without contact with gasoline vapors for 15 minutes. After establishing a constant voltage level of 18 MPa in both film elements (specific surface area of 10 m / kg), one element is brought into contact with

B-70 gasoline vapor. A voltage drop of 10% is observed after 100 s. Determination of gasoline in a known manner is impossible.

Examples 2-5. Pairs are determined

n-pentane in air as in example 1, but fluoronone F-32L film of thickness 5 is used as the adsorption-active polymer; 20; 100; 500 microns or fiber of ftorlon F-2M. Vapor detection time

given in the table.

Examples 6 and 7. Water vapors are determined by known and proposed methods of example 1, using a film of polyamide 6 and cellophane with a thickness of 20 µm.

(specific surface 50 m / kg). The time for determining water vapor in a known manner is 2 minutes, the time for determining water according to the invention on a PA-6 film is 40 s, on a cellophane film 60 seconds.

Example The impurities of ethanol in water (3% solution) are determined by a known method and proposed in example 1 using a 100-µm-thick polyethylene terephthalate film as a sensitive element. One element is immersed in distilled water, the second - in a solution of ethanol. The display time of ethanol in water is 50 s. In a known manner, the indication of alcohol in water is not carried out (water does not differ from ethanol solution).

The examples confirm the higher sensitivity and selectivity of the proposed method, its speed and versatility.

Claims (1)

Claims of Invention A method for determining the content of components in liquid and gaseous media. that a sensitive element is placed in the analyzed medium, a change in its physicomechanical parameter is measured, the value of which determines the content of the analyzed component, differing in that. that, in order to increase the sensitivity, speed and selectivity of determinations, a polymer adsorption-active to the analyzed component is used as the material of the sensitive element; before measuring, the sensitive element is deformed and maintained in the absence of the analyzed component to a constant voltage values, and the change in voltage over time is used as the measured parameter. FIG L 2