Method of determination of the dihydroxybenzenes in the water solutions

FIELD: chemical industry; paint and varnish industry; photographic industry; methods of detection of the dihydroxybenzenes in the water solutions.

SUBSTANCE: the invention presents the method of control over the content of the dihydroxybenzenes in the purified waste waters of the enterprises of the paint and varnish industry and photographic industry. The method provides for detection and determination of the dihydroxybenzenes in the water solutions by the method of the reversed-phase microbore column highly effective liquid chromatography with the preliminary stage of the extractive concentrating at рН 2-3. At that the extractive concentrating of the dihydroxybenzenes is exercised by acetonitrile at the ratio of the equilibrium volumes of the water and organic phases 100:2 at the presence of the salting-out agent of the ammonium sulfate in amount of 36.5-40.0 mass % with respect to the mass of the sampling. The method ensures the increased degree of concentrating, reduction of the detection limits, the decreased consumption of the extractive reactants and the net cost of the analysis.

EFFECT: the invention ensures the increased degree of the concentrating, reduction of the detection limits, the decreased consumption of the extractive reactants and the net cost of the analysis.

2 tbl, 3 ex

 

The invention relates to analytical chemistry of organic compounds and can be recommended for analytical control of the content of chemical compounds in the effluents of enterprises in the paint and photographic industries.

The known method of determination of hydroquinone and metol in aqueous solutions (RU patent 2172952, BI No. 24 27.08.2001). The method assumes that the concentration of the hydroquinone of the analyzed water samples dioxane at a ratio of equilibrium volumes of the aqueous and organic phases and 10:1 in the presence of ammonium sulfate and subsequent determination of the voltammetric method.

The disadvantages of the method - the use of non-standard equipment (three-electrode cell for voltammetric detection), neselektivno, low degree of concentration.

The closest in technical essence and the achieved effect is the method of determination of hydroquinone and pyrocatechin in aqueous solutions (RU patent 2205398, BI No. 15 dated 27.05.2003), which includes the concentration of hydroquinone and pyrocatechin hexane solution trioctylphosphine (TOPO) and define them in separated organic phase by the method of reversed-phase microcolumn liquid chromatography.

The disadvantages of the method: the use of expensive and scarce reagent, TOFU; with whom is very useful for sample preparation (drying of the organic layer in a stream of nitrogen); low degree of concentration (the concentration factor of 10).

An object of the invention is to increase the degree of concentration, lower detection limits, simplifying detection method dihydroxybenzenes in aqueous solutions (by eliminating the stage of preparation of the organic phase), reducing consumption of solvent extraction reagents and cost analysis, as well as extending the scope of its application.

The goal of the project is achieved in that in the method of determining dihydroxybenzenes in aqueous solutions, including the definition of dihydroxybenzenes in aqueous solutions by the method of reversed-phase microcolumn high-performance liquid chromatography with pre-stage extraction concentration at pH 2-3, what's new is that extraction concentration of dihydroxybenzenes carry acetonitrile at a ratio of equilibrium volumes of aqueous and organic phases 100:2 in the presence of vicariates of ammonium sulfate in the amount of 36.5-40.0 wt.% with respect to the sample mass.

The technical result of the invention is to simplify the method by eliminating the stage of preparation of the organic phase (excluded from analysis scarce reagent, TOFU and stage of drying of the organic layer in a stream of nitrogen), the increased degree of con is interevene (the concentration factor of 50), the lower detection limits and flow extraction reagents.

Method of determining dihydroxybenzenes in aqueous solutions as follows.

To 100 cm3water samples containing hydroquinone, pyrocatechin and resorcinol, acidified to a pH of 2.5, add visivel of ammonium sulfate in the amount of 36.5-40.0 wt.% with respect to the sample mass and 2.5 cm3acetonitrile (Korenman YA, Ermolaeva, T.N., Mishina AV and other Triple-chart water - ammonium sulphate - hydrophilic solvent. Lipetsk, 1995. - Dept. In VINITI No. 295-In-95. - 10 C.), extracted on vibromaster 15 minutes After 15 minutes after separation of phases (the ratio of the equilibrium volumes of aqueous and organic phases 100:2) to separate the organic layer and analyze the chromatograph "milikhrom-4" with UV detector. The definition of dihydroxybenzenes carried out by the method of reversed-phase microcolumn high-performance liquid chromatography: column 80×2 mm; sorbent - silsor 18; the particle size of the sorbent 7 μm; mobile phase a mixture of acetonitrile: water in a volume ratio of 20:80; analytical wavelength of 272 nm; flow rate of mobile phase 10-4DM3/min; the volume of injected sample 5×10-6DM3; the analysis time of 15 minutes

The concentration of each dihydroxybenzenes in aqueous solution calculated by the formula:

C=(C0·100)/(R·r),

where the 0- concentration dihydroxybenzene (pyrocatechol, hydroquinone, resorcinol) in the extract, which is found by the method of absolute calibration, mg/DM3;

With the concentration of dihydroxybenzene in the original sample, mg/DM3;

r is the ratio of the equilibrium volumes of aqueous and organic phases;

R is the degree of extraction of dihydroxybenzene in the system acetonitrile - water-salt solution, %.

The degree of extraction of dihydroxybenzenes (R, %) was calculated by the formula:

R=E·100/D+r

where D is the distribution coefficient of dihydroxybenzenes in the system acetonitrile - water-salt solution; r is the ratio of the equilibrium volumes of aqueous and organic phases.

Way feasible. The degree of extraction of dihydroxybenzenes proposed method is 94-96%.

The method is illustrated by the following examples.

Example 1.

Solutions dihydroxybenzoic prepared from drugs qualification "h", purified by sublimation. The degree of purity of drugs controlled by the melting temperature. The original aqueous solutions with accurately known concentration is prepared by the method of dilution of the standard solutions.

To 100 cm3water samples containing hydroquinone, pyrocatechin and resorcinol, acidified to a pH of 2.5, add visivel of ammonium sulfate in the amount of 38.5 wt.% with respect to the sample mass and 2.5 cm3acetonitrile, shaken out on the and vibromaster 15 minutes 15 min after the separation of phases (the ratio of the equilibrium volumes of aqueous and organic phases 100:2) to separate the organic layer and analyze the chromatograph "milikhrom-4" with UV detector. The definition of dihydroxybenzenes carried out by the method of reversed-phase microcolumn high-performance liquid chromatography: column 80×2 mm; sorbent - silsor 18; the particle size of the sorbent 7 μm; mobile phase a mixture of acetonitrile: water in a volume ratio of 20:80; analytical wavelength of 272 nm; flow rate of mobile phase 10-4DM3/min; the volume of injected sample 5×10-6DM3; the analysis time of 15 minutes

The concentration of each dihydroxybenzenes in aqueous solution calculated by the formula:

C=(C0·100)/(R·r),

where C0- concentration dihydroxybenzene (pyrocatechol, hydroquinone, resorcinol) in the extract, which is found by the method of absolute calibration, mg/DM3;

With the concentration of dihydroxybenzene in the original sample, mg/DM3;

r is the ratio of the equilibrium volumes of aqueous and organic phases;

R is the degree of extraction of dihydroxybenzene in the system acetonitrile - water-salt solution, %.

The degree of extraction of dihydroxybenzenes (R, %) was calculated by the formula:

R=E·100/D+r

where D is the distribution coefficient of dihydroxybenzenes in the system acetonitrile - water-salt rest is R; r is the ratio of the equilibrium volumes of aqueous and organic phases.

The distribution coefficients of dihydroxybenzenes determined photometrically at fotoelektrokalorimetry KLF-3 by reaction with diazotized sulfanilic acid.

Way feasible. The degree of extraction of dihydroxybenzenes 94-96%. The data analysis is presented in table 1, 2.

As can be seen from the tables, the concentration factor of 50, which reduces the detection limit of 5 times, the error determination dihydroxybenzoic not exceed 10%.

Example 2.

To 100 cm3water samples containing hydroquinone, pyrocatechin and resorcinol, acidified to a pH of 2.5, add visivel of ammonium sulfate in the amount of 36.5 wt.% with respect to the sample mass and 2.5 cm3acetonitrile, shaken out on vibromaster 15 minutes Further analyze analogously to example 1. Way feasible. The data analysis are presented in table 1, 2.

As can be seen from the tables, the concentration factor of 50, the detection error does not exceed 10%.

Example 3.

To 100 cm3water samples containing hydroquinone, pyrocatechin and resorcinol, acidified to a pH of 2.5, add visivel of ammonium sulfate in the amount of 40.0 wt.% with respect to the sample mass and 2.5 cm3acetonitrile, shaken out on vibromaster 15 minutes Further analyze analogously to example 1. Way feasible. The data and what she presented in table 1, 2.

As can be seen from the tables, the concentration factor of 50, the detection error does not exceed 10%.

When reducing the number of vicariates (less of 36.5 wt.%) released extract contains significant amounts of water, which prevents further definition; the increase in the content of vicariates (more than 40.0 wt.%) leads to the separation of the salt crystals, which absorb dihydroxybenzene. The change in the ratio of the equilibrium quantities in the direction of increasing the organic phase leads to the decrease in the concentration, the decrease in the volume of the organic phase reduces the degree of extraction.

The correctness of the method is tested on model solutions dihydroxybenzoic method "introduced - found". The determination results are presented in table 1. The relative error of determination of pyrocatechin not exceed 10%.

Table 1

The definition of dihydroxybenzenes in aqueous solution (n=5, P=0,95)
Entered, mg/DM3HydroquinonePyrocatechinResorcinol
±σ, mg/DM3Sr±σ, mg/DM3Sr±σ, mg/DM3Sr
that 0 0,080,0780,080,0780,050,049
0,10,00850,0820,0170,160,0160,14

Table 2 shows the comparative characteristics of the proposed method and prototype.

Table 2
Assessment criteriaThe known methodThe proposed method
Easy analysisRequired sample preparation of the organic phase to the analysis (drying of the organic layer in a stream of nitrogen)Sample preparation the organic phase is missing
The coefficient of concentration1050
Defined concentration, mg/DM35,0; 0,51,0; 0,1
The objects of analysisHydroquinone, pyrocatechinHydroquinone, pyrocatechol, resorcinol

The proposed method allows the determination of dihydroxybenzene in aqueous solutions without the stage of preparation of the organic phase, to reduce the consumption of solvent extraction reagents, to increase the degree of concentration, to reduce the detection limit of 5 times, adesivi the b method, and also to widen the application to control the content of dihydroxybenzenes.

Method of determining dihydroxybenzenes in aqueous solutions by the method of reversed-phase microcolumn high-performance liquid chromatography with pre-stage extraction concentration at pH 2-3, characterized in that the extraction concentration of dihydroxybenzenes carry acetonitrile at a ratio of equilibrium volumes of aqueous and organic phases 100:2 in the presence of vicariates of ammonium sulfate in the amount of 36.5-40.0 wt.% with respect to the sample mass.



 

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