RU2239183C1 - Method of determination of content of methyl ethylene ketone in air - Google Patents

Abstract

FIELD: analytical chemistry of organic compounds for detection of methyl ethylene ketone in air of working zones; paint-and-vanish industry, furniture industry and pharmaceutical industry.

SUBSTANCE: proposed method includes selection and preparation of sample and determination of content of methyl ethylene ketone. Method is based on use of piezo-quartz resonator which is preliminarily modified by acetone solution of sorbent of polyethylene glycol succinate at mass of 8-20 mkg; analytical signal is recorded 30 s after introducing the sample.

EFFECT: reduced time required for analysis; avoidance of chemical reagents for analysis.

2 tbl, 7 ex

Description

The invention relates to the analytical chemistry of organic compounds and can be used to determine methyl ethyl ketone in air emissions of paint and varnish, furniture industry enterprises, as well as in the manufacture of pharmaceutical preparations.

Of greatest relevance in modern gas analysis is the direction of creating sensor devices characterized by compactness, selectivity, low detection limits, reliability and ease of operation. About 40% of all sensor devices account for modified piezoelectric quartz resonators.

Photometric is used to determine methyl ethyl ketone in air / I.M.Korenman Photometric analysis. Methods for the determination of organic compounds. - M., Chemistry, 1970, 144 pp. / And gas chromatographic / Drugov Yu.S. Methods of analysis of air pollution. - M .: Chemistry, 1984. S.203 / methods.

The disadvantages of the known methods are lengthy sample preparation (photometry) and complex instrumentation (gas chromatography).

The closest in technical essence and the achieved result to the claimed solution is a method for determining methyl ethyl ketone in air by photometry [Methodological guidelines for the determination of harmful substances in the air. - M., CRIA "Morflot", 1981, 252 p.]. The definition is based on the interaction of methyl ethyl ketone with iodine in an alkaline solution. The resulting thin suspension of iodoform is photometric at 420 nm.

The disadvantage of the prototype is the duration of the analysis and a significant consumption of reagents.

An object of the invention is to reduce the detection limit of methyl ethyl ketone, increase expressivity, the exclusion of chemicals from the analysis.

The stated technical problem is achieved by the fact that in the method for determining methyl ethyl ketone in air, including sampling and preparing a sample, determination of methyl ethyl ketone, it is new that a piezoelectric crystal resonator pre-modified with an acetone solution of a polyethylene glycol succinate (PEGS) sorbent with a mass of 8-20 μg is used to determine methyl ethyl ketone , the registration of the analytical signal is carried out 30 s after the injection of the sample.

The positive effect of the proposed method is achieved due to the fact that the acetone solution of PEGS used as a modifier makes it possible to determine the amount of methyl ethyl ketone in the analyzed air sample. The optimal mass of the sorbent (8-20 μg) contribute to an increase in the sensitivity of the modified piezoelectric crystal and increase the accuracy of determination. The maximum permissible concentration of methyl ethyl ketone in the air is 200 mg / m ³ .

The method for determining methyl ethyl ketone in air is carried out according to the following procedure.

1) Sampling. Sample air containing methyl ethyl ketone is taken into the gas cell for 3 minutes at a rate of 250 cm ³ / min. Through a sealed shutter, 10 cm ^{3 of the} sample is introduced into the detection cell containing a modified piezoelectric crystal resonator on bulk acoustic waves.

2) Sensor preparation. On both sides of the aluminum electrode (diameter 5 mm, area 0.2 cm ² ) of the piezoelectric quartz resonator (AT slice, quartz density 2600 kg / m ³ ) with a natural frequency of 10 MHz, a solution of PEGS in acetone is applied with a syringe so that after evaporation of the solvent in the oven for 5 min at 60 ° C the film weight was 8-20 μg.

3) Determination of methyl ethyl ketone. The modified quartz resonator is placed in the detection cell with an injection injection of the sample. Hold for 3 min to establish a stable zero signal F °. Then, 10 cm ^{3 of} air containing methyl ethyl ketone are introduced into the detection cell with a syringe. The oscillation frequency of the piezoelectric quartz resonator F is fixed 30 s after the sample is introduced. From the difference F ° and F, the resonator response ΔF is calculated

ΔF = F ° -F.

The response of the modified piezoelectric crystal resonator and the equation of the calibration graph find the methyl ethyl ketone content in the analyzed air sample

ΔF = 1.95 · C _M ,

where ΔF is the response of the modified piezoelectric crystal resonator, Hz;

With _M is the concentration of methyl ethyl ketone in the air sample, mg / m ³ .

Examples of the method

Example 1

A solution of PEGS in acetone is applied with a syringe on both sides of the resonator electrode so that the film mass after removal of the solvent in an oven (5 min, 60 ° C) is 8 μg. After drying, the modified piezoelectric crystal is placed in the detection cell with the injection of the sample, the analyzed air sample is introduced, and the resonator response is recorded 1 min after the sample is introduced. The response of the modified piezoelectric crystal resonator and the equation of the calibration curve calculate the methyl ethyl ketone content in the air sample. The method is feasible, the results of the analysis are presented in table 1.

The maximum sensitivity of the modified resonator to methyl ethyl ketone is 1.9 Hz · m ³ / mg;

the detection limit of methyl ethyl ketone is 5 mg / m ³ ;

the duration of the analysis with sampling according to the full scheme with a preliminary modification of the electrodes is 30 min;

the number of analyzes without updating coatings on the electrodes ≈ 80;

the duration of the analysis with sampling on a modified piezoelectric crystal resonator with subsequent regeneration is 10-15 minutes.

Example 2

A solution of PEGS in acetone is applied with a syringe on both sides of the resonator electrode so that the mass of the film after removal of the solvent in an oven (5 min, 60 ° C) is 15 μg. Next, analyze, as indicated in example 1. The method is feasible. The results are shown in table 1.

Example 3

A solution of PEGS in acetone is applied with a syringe on both sides of the resonator electrode so that the film mass after removing the solvent in an oven (5 min, 60 ° C) is 20 μg. Next, analyze, as indicated in example 1. The method is feasible. The results are shown in table 1.

Example 4

A solution of PEGS in acetone is applied with a syringe on both sides of the resonator electrode so that the film mass after removal of the solvent in an oven (5 min, 60 ° C) is 3 μg. Next, analyze, as indicated in example 1. The method is not feasible, since the recorded response (F, kHz) is unstable, a large error of determination. The results are shown in table 1.

Example 5

A solution of PEGS in acetone is applied with a syringe on both sides of the resonator electrode so that the film mass after removal of the solvent in an oven (5 min, 60 ° C) is 30 μg. Next, analyze, as indicated in example 1. The method is not feasible, since a large mass of the film reduces the sensitivity of determining the content of methylethyl ketone in the air. The results are shown in table. 1.

Example 6

A solution of PEGS in chloroform is applied with a syringe on both sides of the resonator electrode so that the film mass after removal of the solvent in an oven (5 min, 60 ° C) is 16 μg. Next, analyze, as indicated in example 1. The method is not feasible. The results are shown in table 1.

Example 7

Another modifier is applied on both sides of the resonator electrode with a syringe — a solution of polyethylene glycol adipate in acetone so that the film mass after removal of the solvent in an oven (30 min, 60 ° C) is 12 μg. Next, analyze, as indicated in example 1. The method is not feasible. The results are shown in table 1.

Some characteristics of the proposed solution and prototype are compared in table.2.

From examples 1-7 and tables 1 and 2, it follows that the positive effect of the proposed method is achieved with a sorbent mass (PEGS) of 8-20 μg (examples 1-3). When reducing and increasing the mass of the sorbent (examples 4, 5), the sensitivity of the modified quartz resonator with respect to methyl ethyl ketone decreases, the error of determination increases. The use of a different solvent modifier (example 6) and a sorbent (example 7) does not allow the determination of methyl ethyl ketone in air.

Thus, the proposed method for the determination of methyl ethyl ketone in air in comparison with the prototype allows you to:

1) greatly simplify the analysis;

2) reduce the detection limits of methyl ethyl ketone by half (to 5 mg / m ³ );

3) reduce the analysis time from 90-60 minutes to 10-15 minutes;

4) to exclude the use of chemicals.

Claims (1)

A method for determining methyl ethyl ketone in air, including sampling and preparing a sample, determining methyl ethyl ketone, characterized in that a piezoelectric crystal is used to determine methyl ethyl ketone, pre-modified with an acetone solution of the sorbent polyethylene glycol succinate with a mass of 8-20 μg, the analytical signal is recorded 30 s after the injection of the sample .