SU792118A1 - Method of quantitative determination of aniline vapour in air - Google Patents

Description

(54) METHOD FOR QUANTITATIVE DETERMINATION OF ANILINE VAPORS IN AIR The invention relates to the field of analytical chemistry, in particular, to methods for quantitative determination of microconcentrations of aniline vapor in the air. A known method for the quantitative determination of an analyte consists in treating the sample to be analyzed with hydrochloric acid, 4-dimethylaminoben-3 aldehyde and photometric measurement of the resulting flj solution. The disadvantage of this method is its complexity, since 4-dimethylamino benzaldehyde is a scarce and expensive reagent. The closest to the described invention by its technical essence and the achieved result is a method for quantitative determination of aniline vapor in air by passing the sample under analysis through a 4-8% solution of furfural in glacial acetic acid followed by photocolorimetry of the resulting f2j solution. The disadvantage of the method is that it does not have a detection sensitivity, an opening type of 0.0025 mg / ml. The aim of the invention is to increase the sensitivity. This goal is achieved by the described method of quantitative determination of aniline vapor in air by passing the sample under analysis through a 4-8% solution of furfural in glacial acetic acid, followed by additional treatment with 35-40% HL M solution of potassium hydroxide, and 4-8% a solution of furfural in glacial acetic acid and a 35–40% solution of caustic potash are taken in a volume ratio of 5–2.5: 1. The method is illustrated by the following examples. Example. A 15 ml 4% solution of furfural in glacial acetic acid is poured into an absorber with an accumulator and 10 dm of aniline-air mixture with a concentration of 0.5 mg / m of aniline is passed through. The concentrated Schiff base on the accumulator rot with the same sensitive liquid, immediately a 35% solution of caustic potassium is introduced into the absorption device and mixed. After 1520 minutes the solution is colorimetrated on a blue light filter and calculated

the co-nitration of aniline in air according to the formula

X -1000 Mt.D + Vcr

; i)

mg / m

V f

"R.p

X - aniline concentration in

solution according to the calibration graph of the photoelectric colorimeter;

V - the volume passed through

absorption device aniline air mixture;

f - correction factor;

Vj, is the volume of sensitive fluid in the absorption device;

V (. Is the volume of stabilizer introduced into the absorption device

In tab. 1 shows the results of studies of the dependence of Cd concentration of aniline in air on the volume ratio of a solution of furfural in acetic acid and a solution of potassium hydroxide.

Table 1

3.05: 1 0.193 0.47 P, 31

0.5

4.53.33: 1 0.190 0.4b 0.30

6.02.5: 1 0.180 0.410.25 The calibration of the photoelectric colorimeter is as follows. A 4% solution of freshly distilled furfural in glacial acetic acid, a 1% alcohol solution of chemically pure aniline, and a 35% solution of potassium hydroxide are prepared. In a 50 ml volumetric flask, pour in a 25 ml (accurately) sensitive solution with a pipette and

The optical density of the solution with the addition of 1% aniline solution and 10 ml of 35% KOH, ml

Table 2 is added respectively 0.05, 0.1, 0.15.0.2 and 0.25 ml of 1% aniline solution. After each addition of the aniline solution, immediately pour 10 ml of a 35% KOH solution into the flask and thoroughly mix the contents of the flasks. After 15-20 minutes The photoelectric colorimeter is calibrated in the usual way on a blue light filter. The results of the calibration of EC-M are given in table. 2

Taking into account that in 1 mp of 1% aniline solution contains 10.22 µg of aniline, a calibration graph for FEC-M is constructed.

The determination of the aniline vapor content in air is carried out as follows. A 25 ml (exactly) 6% solution of furfural is poured into the absorption device with a snooper and a 10 dm aniline air mixture in glacial acetic acid is passed (the volume of the missed analyzed mixture depends on the expected aniline concentration in the air). The resulting Schiff base concentrate is washed off with the same liquid with a rubber pear and 10 ml of a 35% KOH solution are immediately added, the contents are mixed and after the end of the reaction (after about 15-20 minutes) they are colorimetrated. The amount of aniline in 1 ml of the solution is determined from the calibration graph and the content of aniline vapor in the air is determined by formula (1). For example, if according to the calibration graph of Co 0.002 mg / mp, then the content of aniline vapor in the air will be

25 + 10

0,002-1000

Sl

 10-0.93 25 10-0.93 0.3 mg / m

A sensitive liquid is prepared consisting of a 4% solution of furfural in glacial acetic acid.

25 ml of a sensitive liquid are poured into the volumetric flasks and 0.02 and 0.25 ml of 1% aniline solution are added, respectively, and colorimetrated.

The same is done for the proposed method. The research results are summarized in table. 3

Table 3

Claims (1)

The claims 45 A method for the quantitative determination of aniline vapors in air by passing an analyzed sample through a 4-8% solution of furfural in glacial acetic acid followed by colorimetry of the resulting solution, characterized in that, in order to increase sensitivity, the resulting solution is additionally treated with 35-40% caustic soda solution potassium, and a 4–8% solution of furfural in glacial acetic acid and a 35–40% solution of caustic potassium are taken in a volume ratio of 5–2.5: 1.