RU2069352C1 - Method of determining hydroquinone and paraquinone dioxime - Google Patents

Abstract

FIELD: analytical chemistry. SUBSTANCE: sample solution is divided into two portions. To the first one, sodium acetate solution is added followed by measuring optical density of colored solution which value permits one to evaluate paraquinone dioxime content in sample. The second portion of sample is treated with sodium hydroxide solution followed by measuring optical density of solution and thereby estimating summary content of hydroquinone and paraquinone dioxime. EFFECT: achieved quantitative determination of both chemicals in one sample. 1 tbl

Description

 The invention relates to the field of analytical chemistry, and in particular to a method for the quantitative determination of hydroquinone (GC) and dioximparaquinone (DOC) in solutions with their joint presence.

 Known titrimetric methods for the determination of quinones using tetrabutylammonium as a titrant [1, p. 49] chromium salts [1, p. 499] The disadvantage of these methods is their non-specificity, low sensitivity, high resistance, deficiency and toxicity of the reagents used.

The closest in technical essence and the achieved result to the proposed one is a method for the total determination of hydroquinone and dioximparaquinone (oximes), which consists in adding a ferric salt to the sample solution, conducting the reduction of ferric iron with determined substances, adding a color reagent to ferrous iron to the resulting solution and register the optical density of the colored solution, the value of which is judged on the content of these substances in the sample [2, 1970, p. 243]
The method is unsuitable for separate determination of GC and DOC.

 The essence of the invention is that the sample solution is divided into two parts, a solution of sodium acetate is added to the first part of the sample, the optical density of the colored solution is measured and its value is used to determine the content of dioximparaquinone in the sample, sodium hydroxide solution is added to the sample, and the optical density is measured stained solution and its value judges the total content of hydroquinone and dioximparaquinone in the sample.

 Due to the fact that GC stains a solution of sodium hydroxide, but does not stain a solution of sodium acetate, while DOC stains both solutions, the content of DOC is calculated from the results of photometric measurements of the solution with sodium acetate, and the GC content of the difference between the results of photometric measurements of the solution with sodium hydroxide and its fractions, corresponding to the content of DOH.

Three calibration curves of dependence are preliminarily constructed:
a) the optical density of the solution from the content of GC treated with sodium hydroxide,
b) the optical density of the solution from the content of DOC treated with sodium hydroxide,
C) the optical density of the solution from the content of DOC treated with sodium acetate.

 The graph according to item “c” is used to calculate the content of DOC. Schedule "b" determines the proportion of optical density of the sample treated with sodium hydroxide, corresponding to the content of DOC. Graph "a" is used to calculate the content of GC by the difference in the optical density of the sample treated with an alkali solution and its fraction corresponding to the content of DOC.

 Determination of DOC and GC by treating one portion of the sample with a solution of sodium acetate, the other portion with a solution of sodium hydroxide followed by photometry of the colored solutions is a hallmark and are not found in similar technical solutions.

 The claimed technical solution allows to separately determine the DOC and GC in a solution of inhibitors in their joint presence. The good solubility of sodium acetic acid and sodium hydroxide not only in water but also in alcohol allows the analysis of many organic solvents by dissolving the sample in alcohol, eliminating the time-consuming extraction process.

 The presence of distinctive features confirms the novelty of the invention and inventive step.

 The simplicity of analysis, the rapidity, the availability of reagents and equipment used in the claimed method, as well as the need for a method for analytical control of the preparation unit of a styrene production inhibitor solution confirm its compliance with the criterion of "industrial applicability".

The invention is as follows:
In three volumetric flasks with a capacity of 50 cm ^3, 1 3 cm ^{3 of the} test sample containing 0.15 0.3 mg of GC and DOC is added, 25 cm ^{3 of a} solution of sodium acetate in alcohol with a concentration of 1 wt. and in another 25 cm ^{3 of a} solution of sodium hydroxide in alcohol with a concentration of 1% wt. the contents of both flasks are added to the mark with ethyl alcohol and optical densities are measured with a solution λ = 410 ± 10 nm ..

 The mass fraction of DOC in the test sample in percent is calculated using a calibration graph of the dependence of the optical density of the solution on the content of DOC treated with sodium acetate.

где Y_1, Y₂ объемы пробы, взятые на обработку с уксуснокислым натрием и гидроксидом натрия, соответственно;
C₁ количество ДОХ в фотометрируемом растворе, соответствующее оптической плотности пробы, обработанной уксуснокислым натрием.The mass fraction of GC in the test sample is calculated in the following sequence:
a) calculate C $\genfrac{}{}{0ex}{}{\text{doh}}{\text{2}}$ the amount of mg DOC contained in the sample volume Y ₂ taken for measurement with sodium hydroxide according to the formula:

where Y _1, Y ₂ sample volumes taken for processing with sodium acetate and sodium hydroxide, respectively;
C _{1 the} amount of DOC in the photometric solution, corresponding to the optical density of the sample treated with sodium acetate.

b) according to the calibration graph of the dependence of the optical density of the solution on the content of DOC treated with sodium hydroxide, determine the proportion of optical density D $\genfrac{}{}{0ex}{}{\text{doh}}{\text{2}}$ corresponding to the value of C $\genfrac{}{}{0ex}{}{\text{lj [}}{\text{2}}$ .

C) determine the proportion of optical density D $\genfrac{}{}{0ex}{}{\text{u [}}{\text{2}}$ corresponding to the content of GC in the sample taken for processing with sodium hydroxide:
D $\genfrac{}{}{0ex}{}{\text{u [}}{\text{2}}$ = D ₂ -D $\genfrac{}{}{0ex}{}{\text{lj [}}{\text{2}}$ ,
where D _{2 the} optical density of the sample treated with sodium hydroxide.

где C $\genfrac{}{}{0ex}{}{\text{гх}}{\text{2}}$ количество ГХ в фотометрируемом растворе, полученном обработкой пробы гидроксидом натрия, мг; m масса пробы, взятая на обработку с гидроксидом натрия, г.g) the mass fraction of GC in the test sample in percent is calculated by the formula:

where c $\genfrac{}{}{0ex}{}{\text{gh}}{\text{2}}$ the amount of GC in the photometric solution obtained by processing the sample with sodium hydroxide, mg; m is the mass of the sample taken for processing with sodium hydroxide, g

 The invention is illustrated by the following examples.

 Example 1

 Construction of a calibration graph of the dependence of optical density on DOC treated with sodium acetate.

The flasks with 50 cm ³ of making 0.5 1.0 1.5 2.0 - 2.5 3.0 cm ³ of a standard solution of DOX in an alcohol at a concentration of 0.3 mg / cm ³ and 25 cm ³ of poured acetate solution sodium with a concentration of 10 g / dm ³ , add up to the mark with alcohol, mix and measure the optical density of the solution with a blue filter in cuvettes with a layer thickness of 50 mm in relation to the solution of the control experiment, which is prepared in a similar way, but without a standard solution. According to the measurement results (0.09 0.2 0.3 0.38 0.47 0.54), a calibration curve is plotted by plotting the content of LC in the photometric solution in mg along the abscissa axis and the optical densities corresponding to them along the ordinate axis.

 Example 2

 Construction of a calibration graph of the dependence of optical density on DOC treated with sodium hydroxide.

The flasks with 50 cm ³ of making 0.1 0.2 0.4 0.6 - 0.8 1.0 cm ³ standard solution DOX in an alcohol at a concentration of 0.3 mg / cm ³ and 25 cm ³ of poured hydroxide solution sodium with a concentration of 10 g / dm ³ , add up to the mark with alcohol, mix and measure the optical density of the solutions with a blue filter in cuvettes with a layer thickness of 50 mm in relation to the solution of the control experiment, which is prepared under similar conditions, but without a standard solution. According to the measurement results (0.12 0.21 0.34 0.43 0.50 0.56), a calibration graph is constructed by plotting the DOC content in the photometer solution in mg on the abscissa axis and the optical densities corresponding to them on the ordinate axis.

 Example 3

 Construction of a calibration graph of the dependence of optical density on GC treated with sodium hydroxide.

The graph is constructed analogously to example 2, with the only difference being that instead of a standard solution of DOC, a standard solution of GC in alcohol with a concentration of 0.3 mg / cm ^{3 is used} . To plot, the measurement results (0.07 0.11 0.17 0.25 0.32 0.37) are plotted along the ordinate axis, and the corresponding quantities of DOC in the photometric solution in mg are plotted along the abscissa axis.

 Example 4

 An artificial mixture of the composition is analyzed: DOC 0.109 GC 0.219 in ethanol.

5.0 cm ^{3 of the} mixture is diluted to 50 cm ³ with ethanol and stirred.

In a volumetric flask with a capacity of 50 cm ³ (N 1), add 2.0 cm ^{3 of the} diluted mixture, add 25 cm ^{3 of a} solution of sodium acetate in alcohol with a concentration of 10 g / dm ³ , add ethyl alcohol to the mark, mix and photometer with respect to the solution control experiment (25 cm ³ sodium acetate is added to 50 cm ³ ethanol) in a cuvette with a layer thickness of 50 mm at λ = 410 ± 10 nm. The measurement result D = 0.19.

Into a volumetric flask with a capacity of 50 cm ³ (N 2) add 2.0 cm ^{3 of a} diluted sample, add 25 cm ^{3 of a} solution of sodium hydroxide in ethanol with a concentration of 10 g / dm ³ , add alcohol to the mark, mix and measure the optical density of the solution in a cuvette with a layer thickness of 50 mm at λ = 410 ± 10 nm with respect to the control solution (25 cm ³ of sodium hydroxide solution is added to 50 cm ³ with ethanol). The measurement result is D = 0.515.

 The calculations.

2. Рассчитывают содержание ДОХ в объеме, взятом на обработку гидроксидом натрия, мг:

3. По графику из примера 2 находят долю оптической плотности Д_дох, соответствующую содержанию ДОХ; Д=0,29.1. According to the graph from example 1, find the amount of DOC in the photometric solution (C = 0.23 mg) and calculate the content of DOC in the sample:

2. Calculate the content of DOC in the volume taken for treatment with sodium hydroxide, mg:

3. According to the graph from example 2, find the fraction of optical density D _dox corresponding to the content of DOC; D = 0.29.

4. Calculate the optical density corresponding to the content of GC:
D _r = 0.515 0.29 0.225
5. According to the graph from example 3, the amount of C _gh in mg corresponding to the optical density D _{gh is found} . C _gx = 0.165 mg.

Пример 5.6. Calculate the content of GC in the test sample:

Example 5

 The production solution of the inhibitors used in the production of propylene oxide with styrene is analyzed.

2.5 g of sample are diluted to 50 cm ³ with ethanol. 3.0 cm ^{3 of} diluted sample is added to a volumetric flask N 1 with a capacity of 50 cm ³ , 25 cm ^{3 of} an alcoholic solution of sodium acetate with a concentration of 10 g / dm ³ are added, added to the mark with ethanol and the absorbance is measured as described in Example 4. Result measurement: D = 0.095.

In a volumetric flask N 2 with a capacity of 50 cm ³ add 1.0 cm ³ alcohol solution of sodium hydroxide, add ethanol to the mark and photometer, as described in example 4. The measurement result D = 0.3.

The calculations are carried out in the sequence described in example 4. Analysis results
DOH 0.063 wt.

 GC 0.165 wt.

 Example 6

среднее арифметическое значение результатов определений; S воспроизводимость метода (стандартное отклонение); X±tS доверительный интервал; W - относительное стандартное отклонение; n число определений; p доверительная вероятность.In order to determine the metrological characteristics of the methodology, five GC and DOC determinations are carried out in the same sample. The results of determinations and calculations for n = 5 and p = 0.95 are presented in the table, where

arithmetic mean value of the results of the determination; S reproducibility of the method (standard deviation); X ± tS confidence interval; W is the relative standard deviation; n number of definitions; p confidence probability.

Claims (1)

 A method for the photometric determination of hydroquinone and dioximparaquinone in solutions, characterized in that the sample solution is divided into two parts, sodium acetate solution is added to the first part of the sample, the optical density of the colored solution is measured and its value is used to determine the content of dioximparaquinone in the sample, add to the second part of the sample sodium hydroxide solution, the optical density of the colored solution is measured, and the total content of hydroquinone and dioximparaquinone in the sample is judged by its value.

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