RU2549452C1 - Extraction-fluorimetric method of determining phenols in aqueous solutions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes using a demixing extraction system - water-antipyrine-acid, wherein antipyrine and naphthalene 2-sulphonic acid are taken in molar ratio of 1:1, heated to melting point of 97°C, 10.0 ml of the analysed aqueous solution is added to 1 ml of the obtained melt of the organic salt antipyrinum naphthalene-2-sulphonate, intensely shaken and held until demixing into an upper aqueous phase and a lower organic phase and the lower organic phase is analysed for fluorescence intensity.

EFFECT: high sensitivity and reliability of analysis.

1 ex, 3 tbl, 5 dwg

Description

The invention relates to the analytical chemistry of organic compounds and is intended for chemical control of drinking water, water objects, and can also be used in wastewater treatment from phenols.

Known methods for the determination of phenols recommended for water inspections, sanitary-epidemiological stations and wastewater treatment plants, based on the extraction of phenols from aqueous solutions with diethyl ether. The phenol content is determined by:

1. gravimetrically [1];

2. Bromometric with conversion to C ₆ H ₅ OH [2];

3. photometrically using 4-amino-antipyrine with conversion to C ₆ H ₅ OH [3];

4. chromatography in a thin layer (TLC) [4];

5. gas chromatography [4].

Methods 1-3 allow the determination of phenols in total, 4, 5 - individual derivatives of phenols after the stage of concentration on solid polysorbent, followed by elution. All of the above methods have certain disadvantages, the choice of methodology is associated with the tasks of chemical-analytical research of the chemical composition of the controlled object.

As an independent control of the PND standard F 14.1: 2: 4.34-95 [5], they recommend a fluorimetric method for measuring the mass concentration of phenols in samples of natural, drinking and waste water using the Fluorat-02 analyzer. The fluorimetric method is based on the extraction of phenols from water with butyl acetate, their re-extraction into an aqueous solution of sodium hydroxide, and the measurement of mass concentration by phenol fluorescence intensity (Table 1). To build a calibration graph, a number of mixtures are prepared in the concentration range 0.05-1.00 mg / dm ³ , Fig. 1. The disadvantages of the extraction-fluorimetric method (analog):

- firstly, the use of an organic solvent - butyl acetate;

- secondly, preliminary separation of oil products by hexane extraction and the stage of phenol reextraction with sodium hydroxide are necessarily required.

The use of hexane and butyl acetate as toxic organic solvents does not correspond to the methods of "green" analytical chemistry. Hexane and butyl acetate have a density less than water and concentrate the target product on top of the extractor.

We select a prototype — an extraction-photometric method for the determination of phenols using an exfoliating water – antipyrine-sulfosalicylic acid extraction system.

4.0 ml of the analyzed phenol solution (working solution prepared from GSO by the method of sequential dilution) are mixed with 1.0 g of antipyrine (pharmacopeia drug) and 0.5 g of sulfosalicylic acid (analytical grade) in a molar ratio of reactants 2: one. After mixing and delaminating the system into the upper aqueous and lower organic phases, the phenol concentrate in the hydrate-solvate of antipyrine sulfosalicylate is examined for the intensity of optical absorption [5].

To determine the optimal absorption wavelength of phenols, an exfoliating system is prepared in 3 graduated graduated tubes. Additives 12.5 are added to the system; 50.0; 100.0 μg / L of phenol working solution prepared from GSO phenol, respectively. After separation, the organic phase is separated from the aqueous phase. The transmission spectrum of RPs is recorded in the region from 333 to 714 nm (Specord UV - VIS) in a 20 mm thick quartz cuvette relative to the control organic phase without phenol additives (Fig. 2). The optimal absorption wavelength of phenols in the RP of the hydrate-solvate concentrate was chosen within 340 nm. To build a calibration graph, systems with the addition of a phenol working solution (GSO 7254-97) 5.00 were prepared; 10.00; 20.00; 50.00 μg / L, respectively. After delamination and separation of the RP from the water, the optical density of the extracts is measured photometrically (SF-46) at the selected wavelength, Fig. 3. The prototype disadvantages: registration of the analytical absorption signal in the near ultraviolet region of the spectrum (340 nm), the interfering effect of antipyrine compounds with nitrite anions (maximum absorption 365 nm, extinction coefficient 360-420 mol ^-1 · l · cm ^-1 [6], sulfosalicylate iron (III) [1].

The inventive extraction-fluorimetric method for the determination of phenols in aqueous solutions and registration of the analytical signal allows to reduce the detection limit of phenols.

Improving the reliability of the determination of phenols in aqueous solutions and recording the analytical phenol fluorescence signal at an angle of 90 degrees to the direction of the light incident on the measuring cuvette by the calibration graph with the subtraction of the control experiment signal, i.e., fluorescence of the organic phase of the water-antipyrine-naphthalene-2-sulfonic acid system additives of phenols.

Replacing sulfonic acid with naphthalene-2-sulfonic acid ensures the achievement of a new technical result.

SUMMARY OF THE INVENTION

The proposed extraction-fluorimetric method for the determination of phenols in aqueous solutions uses an exfoliating water-antipyrine-organic acid system, characterized by the replacement of one acid, sulfosalicylic acid (SC), with another, naphthalene 2-sulfonic acid (NSC), with a molar ratio of antipyrine and NSC (1: 1) heated to a melting point of 97 ° C, add 1 ml of a melt of the organic salt of naphthalene - 2 antipyrine sulfonate, add 10.0 ml of the analyzed aqueous solution, then shake vigorously and hold until delaminated tions at the top - and bottom aqueous - organic phase and analyzed for fluorescence intensity bottom - an organic phase.

The implementation of the invention

Example

Take 5 g of naphthalene 2-sulfonic acid (NSC) grade “h”, thoroughly clean with a mixture of distilled water and concentrated hydrochloric acid in a volume ratio of 1: 1 in a portion of 10 ml, then filter through mechanical impurities with a pore diameter of 0.1 μm. The filtrate was evaporated to remove traces of volatile phenols. After evaporation, the product is stored at room temperature. The purity of the NSC is very important, since microimpurities of phenolic compounds affect the value of the control experiment (background fluorescence signal of the organic phase of the system without the addition of phenols).

Model exfoliating systems are prepared by controlling the total volume within 11.0 ± 0.1 ml, as follows.

Weighed portions of Antipyrine Ant (0.94 g) and purified Naphthalene 2-sulfonic acid NSC (0.65 g) are placed in a 50 ml quartz cup, heated to a melting point of 97 ° C. As a result of chemical protolytic interaction, an organic salt of naphthalene - 2 antipyrine sulfonate - C ₁₁ H ₁₂ N ₂ O * C ₁₀ H ₇ SO ₃ H is obtained. Initially solid reagents: base (antipyrine, Ant) and acid (naphthalene-2-sulfonic acid NSC) are converted at a molar ratio of 1: 1 into an organic salt of antipyrine sulfonate - C ₁₁ H ₁₂ N ₂ O * C ₁₀ H ₇ SO ₃ H. At a temperature close to the boiling point of water, the salt is a low-melting melt - an analog of an ionic liquid, a light substance colorless, odorless with a density of about 2.3 g / ml, i.e. twice denser than pure water, with a solubility of 0.09 g / 10 g H ₂ O. In the molten state, the salt has a viscous structure and a yellowish color. The resulting melt is poured into a test tube, phenol is added with a working solution, previously prepared from the GSO standard, adjusted with water to a total volume of 11.0 ml. The lower phase in the control sample is a yellowish, fairly mobile liquid. In the presence of iron (III) in water, the organic phase turns red. The volume of the organic phase is within 0.70 ml. The optimal quantitative components providing delamination and volume of the lower phase (0.7 ml), 0.01 mol - 10 mmol of Antipyrine and 0.01 mol - 10 mmol of NSC, with a total volume of 11.0 ml. The delamination takes place in a wide range of concentrations of constituent substances: from 28 to 97 wt.% Water with a ratio by weight of antipyrine (Ant): naphthalene-2-sulfonic acid (NSC) from 25:75 to 70:30 according to [8].

The phenol content is determined by the calibration graph

Iph. = 1.10 + 0.12C [μg / L] (r = 0.981), Fig. 4.

As a control sample, use the organic phase (RP) of the exfoliating system without the addition of phenol. The mass concentration of phenols in the aqueous phase is calculated according to the calibration curve Iph. = 0.014 + 0.331Cph. [μg / L] (r = 0.987), Fig. 5.

A control sample is prepared using the aqueous phase of the model system without phenol addition.

In table 2, the phenol distribution between the aqueous (WF) and organic (RP) phases is observed, according to the results of fluorescence analysis. In table 3, presents the comparative results of the known and proposed methods. The higher phenol content in river water after extraction without an organic solvent is associated with the lower position of the concentrate in the system. The inventive system without an organic solvent is more efficient than butyl acetate, does not require reextraction. According to the reference data [9], the distribution coefficient of phenol in butyl acetate 48.5, in the present method reaches 70 ± 3 (table 2).

Quantitative extraction of phenol in the proposed method is provided by salting out, for example, sodium chloride, is also observed during a single extraction of phenol with a melt of naphthalene-2-sulfonate antipyrine from salt water.

In the inventive method, without an organic solvent, a single extraction is used, which ensures the transition of phenol to the lower phase by 80% and taking into account the average values of R increases (example 1, for salt waters). The RP system without an organic solvent forms a concentrate in the lower phase and also extracts phenols from suspensions (plankton). The RP concentrates iron (III), which can be analyzed photometrically in the same sample (the Fluorat analyzer allows you to obtain an optical density signal).

The inventive method is simple, it does not require preliminary distillation of volatile phenols, separation of petroleum products, the use of solid sorbents or an organic solvent. The lower phase concentrate is used to record the absorption signals of iron (III) and other ions in terms of optical density relative to the control experiment with distilled water.

Literature

1. Lurie Yu.Yu. Unified methods of water analysis // ed. “Chemistry”, M., 1971. 375 p.

2. Mazor L. Methods of organic analysis // M .: "World", 1986, 584 S.

3. Lurie Yu. Yu. Analytical chemistry of industrial and waste waters // M .: Chemistry, 1984, 448 p.

4. Fomin G.S. Water. Chemical, bacterial and radiation safety control according to international standards. Encyclopedic reference book. - 3rd ed., Revised. and add. - M., publishing house "Protector", 2000. - 848 p. S.465-470.

5. Uskova A.Yu., Temerev S.V. Features of the determination of phenols in natural surface waters // Bulletin of Altai State University. 2012.3 / 1 (75). S.207-209.

6. Noskova V.V., Temerev S.V. The use of an exfoliating water-antipyrine-sulfosalicylic acid system in chemical monitoring of nitrite ions // News of Altai State University. 2011.3 / 2 (71). S.148-153.

7. PND F 14.1: 2: 4.117-97 Methodology for measuring mass concentrations of phenols in samples of natural, drinking, and wastewater using the Fluorat-02 analyzer.

8. Petrov B.I., Denisova S.A., Lesnov A.E., Shestakova G.E. Interphase distribution of some elements in the water - antipyrine-naphthalene-2-sulfonic acid system // News of universities. Chemistry and chemical technology. 1999. Vol. 42, No. 1. S 21-23.

9. Korenman Ya.I. The distribution coefficients of organic compounds. - Voronezh: Publishing House of the Voronezh State University, 1992. - 336 p. S.153.

Table 1 No. p / p Sampling point The content of phenols μg / l Photometry, SF-46, λmax = 340 nm Fluorimetry, Fluorate 02-3M one 1 km below bus the bridge 20 ± 4 17 ± 7 2 Kulunda Delta 27 ± 3 30 ± 5 Big Yarovoye Lake 3 150 m west of the plant 47 ± 5 42 ± 3 four 5 km east of the plant 27 ± 7 22 ± 7 5 5 km south of the plant 27 ± 8 30 ± 6 27 ± 8 7 8 km south of the plant 42 ± 3 39 ± 3 The results of the determination of phenols in the Kulunda delta and lake. B. Yarovoye

table 2 No. V _century ml V _оf ml introduced phenol, mcg phenol found, mcg D ± ε (R ± ε),% <D> ± ε <R> ± ε in the water phase in org. phase one 10.0 0.7 1.05 0.36 0.79 33.25 ± 4.5 70 ± 2.7 47 ± 18 76 ± 6 0.33 0.80 0.34 0.79 2 2,50 0.45 2.12 69.9 ± 2.9 83 ± 1,5 0.44 2.18 0.43 2.18 3 5.00 1.29 4.03 42.0 ± 3.3 75 ± 2.7 1.29 3.71 1.30 3.70 four 7.35 1,54 5.69 53.4 ± 1.2 79 ± 3 Distribution of phenols in a water - antipyrine-naphthalene-2-sulfonic acid exfoliating system

Table 3 Sample number Butyl acetate Water - Ant - NSC The phenol content, μg / l one 8.55 ± 0.05 9.10 ± 0.07 2 8.26 ± 0.04 8.85 ± 0.02 3 8.11 ± 0.05 8.78 ± 0.03 The results of determination (n = 3) of phenols in the river. Barnaulka fluorescence method

Claims (1)

Extraction-fluorimetric method for the determination of phenols in aqueous solutions, including the use of a water-antipyrine-acid exfoliating extraction system, characterized in that they take antipyrine and naphthalene 2-sulfonic acid in a 1: 1 molar ratio, are heated to a melting point of 97 ° C, and added to 1 ml of the obtained melt of the organic salt of naphthalene - 2 antipyrine sulfonate 10.0 ml of the analyzed aqueous solution, vigorously shake and incubate until delamination into the upper - aqueous and lower - organic phases and studied the lower organic phase is blown for the fluorescence intensity.

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