SU1749770A1 - Sensitive device for determining content of air ions - Google Patents

Abstract

Use: analytical instrumentation. The invention: a sensitive element is made in the form of a piezoquartz plate with electrodes, onto which a sensitive layer of a 20-25% aqueous solution of sucrose is applied, 1 or 1 table.

Description

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

It is known to determine the concentration of air ions in the air with natural and artificial ionization using air ion counters, which are based on various methods for measuring the characteristics of air ions: mass spectrometric, pulsed, alternating current, aspiration, which are used in special measurements and having. are of limited use. Mass spectrometry and alternating current methods are used primarily in laboratory studies, as well as in creating conditions for strong discharge, which causes a shift in chemical equilibria and changes in the concentrations of individual components, leading to a decrease in the sensitivity of the analysis.

The closest to the proposed technical entity is a sensitive element, made in the form of a piezo-quartz plate with electrodes, on which a layer of sorbent is applied. capable of absorbing a detectable substance. Absorption of a detectable substance by a layer applied to a resonator causes a change in the oscillation frequency of the quartz resonator, and this change is proportional to the concentration of the analyte.

The disadvantage of the known sensing element is low sensitivity to air ions.

The aim of the invention is to increase the sensitivity.

The drawing shows a diagram of the sensing element.

The sensing element for determining the content of air ions in the air is made in the form of a piezoquartz plate with electrodes on which a sensitive layer is applied from a 20-25% aqueous solution of sucrose.

High absorption capacity of the proposed sensitive layer.

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succinic acid oxidation. The sensing element consists of a piezoquartz plate. 1 with silver electrodes 2, to which current flows 3. A sensitive layer A, made of a 20-25% aqueous solution of sucrose, is applied to the plate.

The sensing element works as follows.

When an element is included in the circuit of an electronic generator, a piezoquartz plate 1 with electrodes 2 and a layer sensitive to air ions makes electromechanical vibrations with a high frequency determined by the plate thickness and the mass of the sensitive element. During sorption by the sensitive layer of 4 ions from the air, the mass of the sensitive element changes and the frequency of oscillations is proportional to the concentration of aero ions in the air. The content of azions is determined by the sorption-frequency characteristic of the sensitive element:

D (C aeroions),

where D F F2-Fi is the change in the oscillation frequency of the sensitive element, Hz;

Fi, FZ is the oscillation frequency of the sensitive element before and after the absorption of azroic ions by the sensitive layer, Hz;

C is the concentration of air ions in the air in terms of ozone and oxidants, µg / m,

 To obtain a characteristic, a given concentration of air ions is created in the air, irradiating the hermetically sealed air space of a known volume with an ionizing device for a certain time. Then, in this hermetically sealed air space with a strictly defined concentration of air ions, a piezo sensing element with the proposed sensitive layer, included in the electronic generator circuit, is introduced, and the frequency of electromechanical vibrations is measured. Thereafter, a sorbmon frequency response is constructed as the dependence of the oscillation frequency variation on the concentration of ions,

PRI me R. A 100 μg sensitive layer is made on a piezo sensing element. On analytical weights, 20 g of sucrose brand IC are weighed and loaded into a flask with a capacity of 150–200 ml, where 80 g of distilled water are also placed. The resulting aqueous solution of sucrose at a concentration of 20% is used to form the sensitive layer. Then take a quartz resonator {with a quartz plate area of 1.0 cm and with an oscillation frequency of 900 kHz), on both sides of the quartz plate of which a 20% aqueous solution of sucrose is applied, leaving the edge dry and taking precaution so that both sides of the quartz the plates did not have electrical contact through a 20% aqueous solution of sucrose. The sensitive layer is dried and the piezo sensitive element prepared in this way is used in further analysis, before performing

which builds its sorption-mastic characteristics:

D Fttf (C ions,.

. where D F Fi-F2 - change in the oscillation frequency of quartz, kHz;

FI and Fa are the oscillation frequency of quartz before and after the absorption of azroions, kHz;

C is the concentration of air ions in the air, µg / m3.

The construction of the sorption frequency characteristic is carried out as follows.

Create a given concentration of air ions in the air: 0.03; 0.06; 0.12; 0.30; 0.60; 0.90 and 1.20 µg / m3. For this, the sealed air space (in particular, a 6.5 dm3 desiccator) is irradiated with an ionizing device (for example, an air ionizer IVA. RIGA) for 0.5; 0.2; 0; 5.0; 10.0; 15.0 and 20.0 min

respectively. In order to eliminate the influence of moisture on the readings of the piezoelectric element, a Petri dish with water is placed in the bottom of the desiccator. Then a piezo-sensitive element is inserted into the desiccator, which is included in the circuit of the electronic ge-. nerator, and measure the oscillation frequency of the sensitive element. After that, the sorption-frequency characteristic of the piezo-sensitive element is built and analyzed.

The table shows the effect of the concentration of an aqueous solution of sucrose on the sensitivity of the assay.

From the data in the table, it can be seen that the optimum concentration range of the aqueous sucrose solution is 20-25%.

Claims (1)

Claim 0 A sensitive element for determining the content of aeroions in air, made in the form of a piezo-quartz plate, having an area of 1.0 cm2 and a frequency of 900 kHz with electrodes and a sensitive layer coated on the 5th surface of the plate, characterized in that, in order to increase the sensitivity, the layer is made of a 20-25% aqueous solution of sucrose. T7 -