RU1807371C - Sensitive element - Google Patents

Abstract

Purpose: the invention relates to instrumentation and can be used in the development and operation of devices for the determination of α-epichlorohydrin in air. SUMMARY OF THE INVENTION: A sensing element for detecting epichlorohydrin in air comprises a piezocrystal with two electrodes and a sorbent layer. The sorbent layer is made of a mixture of carbon black with vegetable oil in a mass ratio of 1: 0.5. 2 tab. 3 ill.

Description

The invention relates to analytical instrumentation and can be used in the development and operation of instruments for determining epichlorohydrin in air.

An object of the invention is to provide a sensor for detecting epichlorohydrin in air.

The goal is achieved in that in the sensing element for determining epichlorohydrin in air, comprising a piezocrystal with two electrodes and a sorbing layer, according to the invention, the sorbing layer is made of a mixture of carbon black with vegetable oil in a mass ratio of 1: 0.5,

In FIG. 1 shows a piezocrystalline sensing element, which consists of a piezoelectric quartz plate 1 with silver electrodes 2, to which

soldered down conductors 3. A sensitive layer 4, made of a mixture of carbon black (soot) with vegetable oil, is applied to the plate. A piezocrystalline sensing element, when incorporated into an electronic generator circuit, performs high-frequency oscillations. During sorption by a sensitive layer of 4 epichlorohydrin. From the air, the vibration frequency changes in proportion to the concentration of epichlorohydrin in the air.

The invention is illustrated in FIG. 1-3 and osu. as follows.

First, the piezocrystalline sensing element shown in FIG. 1. For this, a sensitive layer is carried out on a piezocrystalline sensing element, the mass of which must be 90 micrograms. To do this, prepare a mixture of carbon black (carbon black) with grow | 00

about

X |

with xi

oil (GOST 1129-73) in a mass ratio of 1: 0.5. This mixture is used as a sensitive layer, applied to a piezocrystalline sensitive element (a quartz wafer with an area of 1.0 cm2, an oscillation frequency of 900 kHz), which is used in further determinations.

Next, a calibration graph is obtained: A F f (Sehg), where A F - FV - F2 is the change in the oscillation frequency of the piezocrystalline sensitive element before and after absorption of epichlorohydrin, Hz; FI, Fa are the oscillation frequencies of the piezocrystalline absorption of epichlorohydrin, Hz; C is the concentration of epichlorohydrin in air, mg / m3. To this end, a plant is assembled, the circuit of which is illustrated in FIG. 2. The installation consists of a piezocrystalline sensing element 1, a fan 2, a measuring pipette 3, a power supply for the fan 4, an indicator 5, a measuring circuit 6, a power supply 7, a sealed measuring chamber 8, ground stoppers 9, 10, and a heating device 11. Then, in a sealed measuring chamber, pinning through a mer-. a new pipette and evaporation by heating the chamber to 60 ° C for 2.5 minutes create the desired concentration of epichlorohydrin; 0.05; 0.1; 0.15; 0.20; 0.25 mg / m3. After creating a given concentration of epichlorohydrin in the measuring chamber, after 5-10 seconds, the AF frequency of the electromechanical vibrations of the piezocrystalline sensitive element with the sensitive layer of a mixture of carbon black (soot) with vegetable oil is measured. Based on the data obtained, a calibration graph is constructed (see Fig. 3 ), with the help of which the concentration of epichlorohydrin in air is determined by placing

5

0

5

0

5

0

a crystalline sensing element with a sensitive layer of a mixture of technical soot and vegetable oil (1: 0.5), connected to the measuring circuit, into the analyzed air space and measuring the readings AF after 5-10 seconds. For example, it turned out that A F 550 Hz. Using the calibration graph shown in FIG. 3, we find that the indicated value corresponds to the concentration of epichlorohydrin in the air, equal to 0.27 mg / m3,

Similarly, the concentration of epichlorohydrin in other samples with different concentrations was determined. The results are shown in table. 1.

From the table it follows that the sensitivity of the proposed sensitive element is 2 times higher than the prototype. Table 2 presents comparative data for determining the content of epichlorohydrin in air using the sensor element proposed by the authors and the prototype. Table analysis 2 shows that in the proposed sensor element, in comparison with the prototype, the detection sensitivity is 2 times higher.

The method is simplified: the number of operations is reduced from 4 (in the prototype) to 1; the analysis time is reduced from 120-150 minutes (in the prototype) to 0.5-1.0 minutes with the proposed sensor element.

SUMMARY OF THE INVENTION

A sensing element comprising a piezocrystal with two electrodes and a sorbent layer, characterized in that, in order to determine epichlorohydrin in air, the sorbent layer is made of a mixture of carbon black with vegetable oil in a mass ratio

1.0-0.5.

i

Table 1

Experimental data for determining the content of epichlorohydrin in the air

51807371 6

Table.2 The number of operations and the duration of the analysis of air for epichlorohydrin

Name

Suggested sensing element

Number of analysis operations Analysis duration,

min

Prototype

1

0.5-1.0

120-150

, g

/ L

about or

C10

C o, Q iTii 0.17

/ T / 1

 sij