RU2065598C1 - Method of determination of oxyderivatives of benzene in aqueous solutions - Google Patents

Abstract

FIELD: analytical chemistry. SUBSTANCE: method of determination of oxyderivatives of benzene in aqueous solution consists in treatment of analyzed sample with nitriding agent - 10% solution of potassium nitrate in concentrated sulfuric acid for not longer than 15 min. Volumetric ratio of analyzed solution and reagent amounts to 0.025-1:0.5. Then mixture is injected with 10% solution of sodium hydroxide to obtain alkaline reaction. Colored solution is scanned photometrically and content oxyderivatives of benzene is calculated. EFFECT: improved reliability of method. 4 tbl

Description

 The invention relates to analytical chemistry, and in particular to methods for the determination of oxybenzenes, and can be applied in the practice of the control and analytical service of chemical plants, when conducting sanitary-hygienic and chemical-toxicological studies. The method belongs to the mass.

A known method for the determination of oxybenzene (phenol), which consists in processing the analyte with 2,6-dibromoquinonechlorimine in an aqueous alkaline medium (pH 9.2), followed by photometry of the resulting colored solution [1]
The method is characterized by a relative execution time, insufficient stability of the colored product and low accuracy of determination.

A known method for the determination of oxybenzenes (phenols) by dissolving the analyzed sample in glacial acetic acid, treating with a mixture of concentrated sulfuric and nitric acids under heating at 100 ^° C, cooling the reaction mixture, followed by diluting it with water, alkalizing with ammonia solution, re-diluting with water and photographing the resulting stained solution [2]
The method is laborious and not high enough sensitivity.

The closest is a method for the determination of phenols (oxybenzenes) in water, which consists of adding dilute nitric acid to an aqueous solution of the analyte cooled to 13-15 ^° C for 30 minutes, keeping the reaction mixture for one hour, followed by adding an aqueous solution of ammonium hydroxide and by photometry of the resulting colored solution [3]
The method is characterized by a significant investment of time for analysis (more than 1.5 hours) and insufficiently high sensitivity (1 • 10 ^-5 mol / l).

 The objective of the invention is to reduce the duration of determination and increase sensitivity.

 The method is as follows.

 An aqueous solution of the analyte is treated with a 10% solution of potassium nitrate in concentrated sulfuric acid at a volume ratio of the analyzed solution and reagent 0.025 1: 0.5, a 10% sodium hydroxide solution is added to the reaction mixture until an alkaline reaction, and the resulting colored solution is photographed .

 The results of determining the optimal ratio of the volumes of the analyzed solution and the reagent in the reaction mixture are presented in table 1.

 The invention is illustrated by the following examples.

 Example 1

 Qualitative determination of oxybenzene.

1 ml of a 0.002% aqueous solution of oxybenzene and 0.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added to the test tube. In 1
For 2 minutes, 8 ml of a 10% sodium hydroxide solution are added to the contents of the tube. A yellow stain appears. The sensitivity of the reaction is 1 • 10 ^-6 mol / L.

 Quantitation.

 Construction of a calibration graph.

 In six volumetric flasks with a capacity of 50 ml, 0.25, 0.5, 1.0, 2.0, 3.0, 4.0 ml of a 0.004% aqueous solution of oxybenzene and, respectively, 4.75, 4.5, 4, 0, 3.0, 2.0 and 1.0 ml of water.

2.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added to each flask, and after 3 minutes the contents of the flasks are adjusted to the mark with a 10% sodium hydroxide solution. The resulting colored solutions are photometered on a KFK-2 instrument at a wavelength of 400 nm in a cuvette with a working layer thickness of 20 mm. The optical density measurements are carried out against the background of the solution obtained in the control experiment. Based on the measurement results, a calibration graph is built. The basic law of light absorption is observed in the concentration range 0.2 to 3.2 μg / ml. The least squares method calculates the equation of the calibration graph, which in this case has the form:
D 0.15101 • C + 0.0427,
where D is the optical density,
With the concentration of the analyte in the photometric solution, μg / ml.

 Method of determination.

 About 0.05 g (accurately weighed) of oxybenzene is dissolved in water in a 50 ml volumetric flask and the total volume is adjusted to the mark with water (solution A). 1 ml of solution A is transferred to a 50 ml volumetric flask and made up to the mark with water (solution B). 4 ml of solution B is added to a volumetric flask with a capacity of 50 ml, 1 ml of water, 2.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added and further operations are carried out according to the scheme described for constructing a calibration graph. The results of the determination and metrological characteristics are presented in table 2.

 Example 2

 Determination of 1,3-dioxibenzene.

 1. Qualitative definition.

1 ml of a 0.002% aqueous solution of 1,3-dioxibenzene and 0.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added to the test tube. After 1 2 minutes, 8 ml of a 10% sodium hydroxide solution are added to the contents of the tube. A yellow stain appears. The sensitivity of the reaction is 1 • 10 ^-6 mol / L.

 2. Quantification.

 Construction of a calibration graph.

In six volumetric flasks with a capacity of 50 ml, 0.25, 0.5, 1.0, 2.0, 3.0, 4.0 ml of a 0.004% aqueous solution of 1,3-dioxibenzene and, respectively, 4.75, 4 are added 5, 4.0, 3.0, 2.0 and 1.0 ml of water. 2.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added to each flask, and after 3 minutes the contents of the flasks are adjusted to the mark with a 10% sodium hydroxide solution. The resulting colored solutions are photographed on a KFK-2 instrument at a wavelength of 400 nm in a cuvette with a working layer thickness obtained in the control experiment. Based on the measurement results, a calibration graph is built. The basic law of light absorption is observed in the concentration range 0.2 to 3.2 μg / ml. The least squares method calculates the equation of the calibration graph, which in this case has the form:
D 0.11869 • C + 0.04621,
where D is the optical density,
With the concentration of the analyte in the photometric solution, μg / ml.

 Method of determination.

 About 0.05 g (accurately weighed) of 1,3-dioxibenzene is dissolved in water in a 50 ml volumetric flask and the total volume is adjusted to the mark with water (solution A). 1 ml of solution A is transferred to a 50 ml volumetric flask and made up to the mark with water (solution B). 4 ml of solution B is added to a volumetric flask with a capacity of 50 ml, 1 ml of water, 2.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added and further operations are carried out according to the scheme described for constructing a calibration graph. The results of the determination and metrological characteristics are presented in table 3.

 Example 3

 Determination of 2-hydroxybenzoic acid.

 1. Qualitative definition.

1 ml of a 0.002% aqueous solution of 2-hydroxybenzoic acid and 0.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added to the test tube. After 1 2 minutes, 8 ml of a 10% sodium hydroxide solution are added to the contents of the tube. A yellow stain appears. The sensitivity of the reaction is 1 • 10 ^-6 mol / L.

 2. Quantification.

 Construction of a calibration graph.

In five volumetric flasks with a capacity of 50 ml add 0.125, 0.25, 0.50, 1.0, 2.0 ml of 0.01% aqueous solution of 2-hydroxybenzoic acid and, accordingly, 2,375, 2.25, 2.0, 1.5 and 0.5 ml of water. 2.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added to each flask and after 15 minutes the contents of the flasks are adjusted to the mark with a 10% sodium hydroxide solution. The resulting colored solutions are photographed on a KFK-2 instrument at a wavelength of 400 nm in a cuvette with a working layer thickness of 20 mm. The optical density measurements are carried out against the background of the solution obtained in the control experiment. Based on the measurement results, a calibration graph is built. The basic law of light absorption is observed in the concentration range 0.25 to 4.0 mg / ml. The least squares method calculates the equation of the calibration graph, which in this case has the form:
D 0.11527 • C + 0.06933,
where D is the optical density,
C is the concentration of the analyte in the photometric solution.

 Method of determination.

 About 0.05 g (accurately weighed) of 2-hydroxybenzoic acid was dissolved in a 50 ml volumetric flask and the total volume was adjusted to the mark with water (solution A). 1.25 ml of solution A was transferred to a 25 ml volumetric flask and made up to the mark with water (solution B). 2 ml of solution B is added to a 50 ml volumetric flask, 0.5 ml of water, 2.5 ml of a 10% solution of potassium nitrate in concentrated sulfuric acid are added, and further operations are carried out according to the scheme described for constructing a calibration graph. The results of the determination and metrological characteristics are presented in table 4.

The method reduces the analysis time by 6–20 times (from 100–110 minutes to 5–18 minutes) and increases the detection sensitivity by a factor of 10 (the opening minimum decreases from 1 • 10 ^-5 mol / L to 1 • 10 ^-6 mol / L). TTT1 TTT2

Claims (1)

 A method for determining benzene oxy derivatives in aqueous solutions by treating the analyzed solution with a nitrating agent, followed by adding an inorganic base solution to an alkaline reaction of the medium and photometric the resulting colored solution, characterized in that a 10% solution of potassium nitrate in concentrated sulfuric acid is used as nitrating agent, treatment with a nitrating agent is carried out for no more than 15 minutes at a volume ratio of the analyzed solution and reagent 0.025 1: 0.5, and as a sol Inorganic base ora use a 10% sodium hydroxide solution.

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