SU1427260A1 - Method of quantitative analysis of formaldehyde in air - Google Patents

Abstract

The invention relates to analytical chemistry, in particular the quantitative determination of formaldehyde in various environmental objects. The analysis is conducted by introducing into the sample hydrochloric hydrazine (20-28 μg / ml), followed by treatment with a solution of disodium chromotropic acid and concentrated HjSO when heated to. The resulting solution is then photometrized. These conditions allow an increase in the sensitivity of the assay to 0.25 µg in a sample with better determination accuracy (relative error 2 against 10% in the known method). 3 tabl

Description

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The invention relates to analytical chemistry, and specifically to methods for determining formaldehyde in various environmental objects.

The purpose of the invention is to increase the sensitivity and accuracy of the method

The method is carried out as follows.

To 2.5 ml of a sample of the analyzed solution in a tube with a ground plug containing 2.00 µg of formaldehyde, 0.2 ml of a 0.1% solution of hydrazine hydrochloric acid (which is 24 µg / ml of sample) is poured, then 0, 5 ml of a 2% aqueous solution of dimeric salt of chromotropic acid and with stirring 5.0 ml of concentrated sulfuric acid (, 83). Hold the tube for 12 minutes in a boiling water bath, cool and measure the light absorption in a single-centimeter cuvette at 570 nm against a blank solution. 1.98 µg of formaldehyde in the sample. The relative error is%.

The determination of formaldehyde in a known manner under the same conditions (the quality and quantity of chemicals are the same) gives the results: the amount of formaldehyde is 1.75 µg, which corresponds to an error of determination of 12.5%

Under the same conditions, comparative experiments are carried out - for different formaldehyde content in samples from 0.25 to 8.00 µg

Table 1 shows the results of determining formaldehyde as a function of its concentration in a sample,

Table 2 shows the results of experiments on the effect of the amount of hydrazine on the accuracy of formaldehyde in a photocalorimetric method.

Maximum accuracy is achieved by adding hydrazine in the amount of 20-28 µg / ml of sample. .

The range of the amount of added hydrazine in the sample is 20-28 µg / ml;

than 20 µg / ml of hydrazine, the completeness of the binding of the impurities present is not achieved, and in the presence of hydrazine greater than 28 µg / ml, hydrochloric acid is formed, which destroys formaldehyde, reducing its concentration. In the range of 20-28 μg / ml of hydrazine, the results are almost identical.

B-tab. 3 shows the results of the determination of formaldehyde by known and proposed methods using clean and contaminated solutions of the chromotropic acid sodium salt.

From TabLo 3 it can be seen that the use of hydrazine repeatedly reduces the error in the determination of formaldehyde and allows, without any purification, to use even stale solutions from long-stored salt for analysis (salt was used for 33 years).

The proposed method for the quantitative determination of formaldehyde provides, in comparison with the known method, an increase in sensitivity up to 0.25 µg in the analyzed sample (by a known method of 1 µg in the analyzed sample) and an increase in accuracy by 2-10 times depending on the initial concentration of formaldehyde.

Claims (1)

Invention Formula The method of quantitative determination of formaldehyde by treating the sample being analyzed with a solution of chromotropic acid disodium salt and concentrated sulfuric acid when heated in a boiling water bath, followed by photometry of the solution obtained, is different from the fact that, in order to increase sensitivity determination, in the analyzed sample preliminarily introduced hydrochloric hydrazine in the amount of 20-28 µg) per 1 ml sample Table 1 0.25 Not detected. The method is not sensitive. 0.50 0.65 0.30 20 thirty 0.55 eleven table 2 The solution is made from purified coli. Table3