SU1385047A1 - Method of determining indol in the air - Google Patents

Abstract

This invention relates to analytical chemistry, in particular to the determination of indole in air. The purpose of the invention is to increase the accuracy of sensitivity and selectivity of determination, reduce the analysis time and; its simplification. The determination of indole is carried out by absorbing it from an air sample with a mixture of acetic acid and 1-3% taken in a volume ratio of 4-1: 1. The resulting solution is heated in a boiling water bath for 10–15 min, followed by photometry of the resulting colored solution. The sensitivity of the method is 2 times higher, the maximum error does not exceed 20%. 6 tab. with S cl

Description

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The invention relates to analytical chemistry, in particular, to methods for determining the microcritical concentrations of indole in the air.

The aim of the invention is to improve the accuracy of sensitivity and selectivity of determination, to reduce the analysis time and simplify it.

The method is carried out as follows.

The analyzed air in the amount of 2 liters is aspirated through two successively connected absorption devices containing 6 ml of each mixture.

five

(acetic acid: diluted nitric acid 4: 1), at a rate of 0.15-0.20 l / min. For the analysis, 5 ml solution is taken in test tubes, the samples are placed for 10 min in a boiling water bath. The resulting pink-crimson solutions are photometrical in a cuvette with a layer thickness of 1 cm at 490-500.

IQ The content of indole in the sample is found on the calibration graph. To build the latter, one-stage solutions of indole in acetic acid with a content of 50 µg / ml are prepared (see

5 standards, Table 1).

Table 1

Standard number

ETENBIPEE

0.0 0.05 0.1 0.2 0.4 0.6 0.8 1.0

.

4,0 3-, 95 3,9 3,8 3,6 3,4 3,2 3,0

,

0.0 2.5 5.0 10.0 20.0 30.0 40.0 50.0

All tubes are added with 1 ml of 1% nitric acid and then proceed as in the determination of samples.

Table 2 presents the dependence.

Table 3 shows the dependence of optical density on the ratio of acetic and 1% nitric acid.

Table3

TableD

 Table 5 presents the dependence of the optical density on the heating time of the absorption solution. Table 5

Table 6 summarizes the results of the determination of the indole according to the proposed and known methods using standard solutions.

Table

above, the maximum error does not exceed 20%. Substances having a structure close to indole (pyrrole, dibenzpyrrole, as well as those that can be encountered under production conditions), naphthalene and its derivatives, fluorene, diphenylene oxide, thionaphthene, etc. do not form colored reaction products under the conditions suggested for the determination of indole, which allows the compound to be selectively determined.

The proposed method involves working with available reactants (acetic acid and nitric acid), eliminates a multistep, leading to the loss of a substance, and consequently, to lower accuracy and reproducible. ti.

The analysis time is significantly shortened.

Claims (1)

Formula izob. reteni The method of determining indole in air by treating an analyte with chemical reagents in an acetic acid medium followed by photometry of the obtained colored solution, which differs: with the aim of increasing the accuracy of sensitivity and selectivity of determination, reducing the time of analysis and its simplification, processing the wire the absorption of an analyte from an air sample with a mixture of acetic acid and 1-3% nitric acid, taken in a volume ratio of 4-1: 1 and obtained Before photometry, the thief is heated in a boiling water bath for 10–15 min.