SU789709A1 - Method of quantitative determination of bis-(octafluoropentyl)-carbonate traces in air - Google Patents

Description

one

The present invention relates to analytical chemistry, namely, to methods for the quantitative determination of bis-octafluoropentyl carbonate in

the air.

A known method for the quantitative determination of esters by saponification of the sample being analyzed, followed by treatment with para-dimethylaminobenzaldegam and colorimetry the obtained colored solution lj.

The disadvantage of the method is the impossibility of determining the bis-octafluoropentyl carbonate in the air.

The closest to the described invention by its technical essence and the achieved result is a method for quantitatively determining trace impurities of bis-octafluoropentyl carbonate in the air by treating the sample being analyzed with a water-alcohol solution of potassium hydroxide, the excess of which is titrated with t2j acid.

The disadvantage of this method is low sensitivity and poor selectivity of determination; chlorides, nitriles and amides of various organic compounds interfere with the determination.

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

The goal is achieved by the described method of quantitative determination of bis-octafluoropentyl carbonate in air, which consists in preliminary absorption of the analyzed sample with ethyl alcohol and melting at 100-220 seconds in the presence of a 2-10% caustic soda solution and treating the resulting melt with water and hydrochloric acid to pH 1.2-1.4 and the thorium-arsenose complex, followed by spectrophotometry of the colored solution obtained.

The method is illustrated by the following example.

3 liters of air containing bis20 octafluoropentyl carbonate are drawn through two successively connected absorbing devices containing 3 ml of ethyl each.

25 each.

The contents of each absorbent instrument are analyzed separately. The colorimetric tubes with thin sections are drained of the contents of the absorber 3Q instruments. Devices wash 0.5 ml.

alcohol, which is poured into the same tubes. 0.3 ml of a 10% sodium hydroxide alcohol solution is poured into each tube. The tubes are shaken and placed in a boiling water bath until the alcohol has completely evaporated. Under the same conditions, a blank experiment is conducted.

After evaporation, the tubes are tightly closed with stoppers and placed in a sand bath, where they are fused at a temperature of 140 for 20 minutes.

After cooling, 5 ml of distilled water is poured into the tubes and shaken until the alloy is completely dissolved. For analysis, depending on the concentration, from 1 to 5 ml of the test solution is taken. Then 1 n hydrochloric acid is added to the tubes until the pH of the medium is 1.4. The amount of hydrochloric acid is established in the control experiment, the pH is monitored on a pH meter.

At the same time, a scale of standards for the determination of ion is prepared, for which, in a series of tubes, a standard solution of sodium fluoride (10 µg / ml) is poured in quantities corresponding to 0.5, 1.0, 3.0, 5.0, 7.0 and 10 µg of fluorine with an aliquot portion from each blank equal to the aliquot portion taken for analysis added to each tube

samples. 0.2 ml of a thorium nitrate solution and 0.2 ml of a 0.025% arsenazo solution are added to all test tubes of the scale and samples. The solution is stirred and after 5 minutes the sample colors are compared with the standard scale or the optical density of the solutions in the cuvette is measured with a layer thickness of 1.0 cm at 578 nm.

The concentration of bis-octafluoropentyl carbonate (X) in mg / m of air is calculated by the formula

x-i-bJL

. 1 IQ

5 where C is the amount of fluorine. Found in the analyzed volume (μg);

Y, is the total volume of the sample; K - sodium fluoride recalculation coefficient for bisooctafluoropentylcarbonate,. found experimentally

and equal to 5; Y is the sample volume taken for ana

liza, (ml);

Y is the volume of air (L) selected for analysis and reduced to normal conditions.

The results of the determination of bis-octa-fluoropentyl carbonate (BA-2) are presented in Table 1.

 Table

As can be seen from the table, the proposed method allows the determination of bis-octafluoropentyl carbonate with high accuracy, which is of great importance in the analysis of trace amounts of substances.

The sensitivity of the determination is 0.5 µg of fluorine in the determined volume of LM.

The method is specific in the presence of 55 nitriles and amyls of various acids,

Table 2 shows the results of the determination of the optical density of BC-2 at the boundary and optimal parameters of the regime.

As can be seen from the table, the boundary and optimal values of the parameters lie within the limits, the temperature is 100-220 ° C, the optimum is 140-180 ° C, the time is 20-40 min, the optimum is 30-40 min, the concentration of the alcoholic solution of NaOH is 1-10%, optimal - 2.0-10.0%.

Claims (2)

Invention Formula The method of quantitative determination of bis-octafluoropentyl carbonate trace impurities in air using an alkaline treatment, characterized in that, in order to increase the sensitivity and selectivity of the determination, analyze Table 2 my sample is pre-absorbed 25 with ethyl alcohol, fused at 1AO-220-C in the presence of 2-10% caustic soda alcohol solution and the resulting melt is treated with water and hydrochloric acid to pH 30 1.2-1.4 and a thorium-arsenose complex, followed by spectrophotometry of the obtained colored solution. Information sources, 35 taken into account in the examination, 1. E. Peregud. Chemical analysis of industrial enterprises air. Chemistry, 1, 1976, p., 187-189. 2. Kritchfield F. Analysis of the main 40 functional groups in organic compounds. M., Mir, 1965, p. 201-203, (prototype).