SU1559284A1 - Method of separating determination of phenol and salicyclic acid in their mixture in aqueous solutions - Google Patents

Abstract

This invention relates to analytical chemistry, in particular to the separate quantitative determination of phenol and salicylic acid in their mixture in aqueous solutions. The goal is to increase the accuracy of determination and reduce the duration of the method. The definition includes the extraction of mixtures with an organic solvent, which has the following ratio of components, mol%: triisobutyl phosphate 50-60, hexane 40-50. Extraction is first carried out at a pH of 7-9, the extract is separated, then at a pH of 1.5-2.0, followed by photometric measurement of each of the extracts. The method allows to reduce the detection limit of the test substances as compared with the known method from 0.005 to 0.0001 mg / ml, i.e. more than a dock. 4 tab.

Description

This invention relates to the analytical chemistry of organic compounds and can be used in the analysis of treated wastewater from chemical and pharmaceutical industries containing phenol and salicylic acid.

The purpose of the invention is to improve the accuracy of determination and reduce the duration of the separate determination of phenol and salicylic acid in aqueous solutions.

The method is carried out as follows.

The pH of the aqueous solution containing phenol and salicylic acid is adjusted to 7-9 and extracted with phenol with an organic solvent consisting of triisobutyl phosphate (5060 mol.%) And hexane (40-50 mol.%). After separation of the phases (5-10 minutes), the extract containing phenol is separated. The aqueous solution is then acidified to a pH of 1.5-2 and salicylic acid is extracted with the same extractant. The optical density of the extracts was measured spectrophotometrically with respect to the pure mixed extractant saturated with water. The content of phenol and salicylic acid is found according to the calibration graphs constructed from standard solutions of the detected substances.

The preparation of the extractant is carried out by mixing 6.8-7.6 ml of triisobutyl phosphate (50-60 mol.%) With 2.4-3.2 ml of hexane (40-50 mol.%).

Example 1. To 150 ml of an aqueous solution containing phenol and salicylic acid, add 1-2 drops of 1 M sodium hydroxide solution to a pH of 7-9, and 10 ml of an organic solvent consisting of triisobutyl phosphate (50 mol% ) and gusan (50 mol,%), and shaken for 20 min. At the same time, the phenol is almost completely transferred to the organic phase, which is separated after separation of the system (after 5-10 min). The optical density of the extract is found spectrophotometrically relative to the extractant saturated with water (ft 273 nm, cm). The concentration of phenol is calculated according to the calibration curve (constructed from standard solutions of phenol in the mixed extract

To an aqueous solution containing salicylic acid is added 1-2 ml of hydrochloric acid (, 639 g / l) to a pH of 1.5-2.0 and 5 ml of an organic solvent consisting of triisobutyl phosphate (50 mol %) Hexane (50 mol.%) The solution is shaken for 20 minutes. At the same time, salicylic acid almost completely passes into the organic phase, the optical density of which is measured spectrophotometrically relative to the mixed extractant saturated with water (305 nm, cm) salicylic acid are found according to the calibration graph, built according to the standard salicylic acid solutions in a mixed extractant,

The duration of the anal for the separate determination of phenol and salicylic acid in aqueous solutions does not exceed 1 hour, accuracy of 6-12%. Examples 2-5 are performed analogously to example 1,

Separate determination of phenol and salicylic acid in single solutions (, 95) for examples 1-5 is given in Table 1.

When conducting a selective extraction from an aqueous solution containing phenol and salicylic acid, various volumes of organic solvent were used (10 and 5 ml). The ratio of the volumes of the aqueous and organic phases is chosen in order to achieve almost complete extraction of the components. This effect is

The development of phenol (95-96% recovery) is achieved when the volume ratio of the phases is 15: 1 (in the examples, 150 ml of an aqueous solution and 10 ml of an organic solvent). Extractive efficacy. the organic solvent for salicylic acid is higher than for phenol, therefore the ratio of phase volumes is increased to 30: 1 (in examples, 150 ml of an aqueous solution and 5 ml of an organic solvent) 0

The degree of phenol and salicylic acid recovery (R,%) is calculated by the equation

R

100%,

P

five

five

0

five

where C is the initial concentration of phenol or salicylic acid in the analyzed aqueous solution, mg / ml;

Cn is the concentration of phenol or salicylic acid in the organic phase, found according to the calibration curve, mg / ml; t. ratio of volumes of water and

organic phases.

From the data it follows that the separate determination of phenol and salicylic acid is optimal. The following extractant composition is used: trisnobutyl phosphate 50-60 mol% hexane 40-50 mol%. A change in the ratio of the components of the proposed extractant in the direction of increasing the hex — by more than 50 mol,% leads to a decrease in the degree of phenol recovery. An increase in the amount of triobiobutyl phosphate in the extractant is above 60 molv%, although it leads to a slight increase in the recovery of the compounds detected, but it is accompanied by the formation of stable emulsions in the aqueous phase which is difficult to be separated by physical methods. spectrophotometric determination of the test substances, while reducing the accuracy of

The experimental data on the determination of phenol and salicylic acid in a known manner by reaction with diazotized 4-nitroaniline (PVZ, Р “0.95) are given in Table 2.

From the data presented in Tables 1 and 2 it can be seen that the accuracy of determination of fe51

nola and salicylic acid by the proposed method is higher than the known. The relative error in the determination of the studied compounds by the proposed method does not exceed 12%, while the known 25-38%. The sensitivity of the proposed method is almost two orders of magnitude higher. Minimum concentration of phenol and salicylic

acid, determined in a known manner with a relative error of 34-38%, is 0.005 mg / ml. The proposed method, with a relative error of no more than 12%, makes it possible to determine components at concentrations of 0.001 mg / ml. Experimental data characterizing the degree of extraction of phenol and salicylic acid (R,%) with an extractant consisting of 50 mol.%. triisobutyl phosphate and 50 mol.% hexane, depending on the pH of the aqueous solution when the content of components is 0.0001-0.001 mg / ml are given in the table. 3,

From Table 3, it can be seen that the pH values ensuring maximum (97–98%) recovery of salicylic acid are in the range of 1.5–3.0, while the corresponding pH values providing the greatest degree of phenol recovery ( 95-96%) are 1.5-9.0.

The proposed method initially extracts phenol, therefore pH 7–9 is optimal, a decrease in phenol recovery is observed at pH 9, and an increase in salicylic acid recovery occurs at pH 1–7 and salicylic acid will pass into the extract along with phenol undesirable with joyful determination.

Table 4. shows the comparative characteristics of the known and proposed methods.

As can be seen from the comparative characteristics of the known and proposed methods (table, 4) and from the experiment

0

five

0

five

0

The data presented in Tables 1 and 2, the application of the proposed method reduces the duration of the analysis from 4-5 hours to 1 hour, reducing the number of consecutive extractions necessary for the almost complete separation of phenol and salicylic acid from 6 to 2, while eliminated rezkstraktsii stage. Reducing the number of consecutive extractions reduces the error in determining phenol and salicylic acid by a factor of 2-3.

The use of an extractant consisting of triisobutyl phosphate (50-60 mol.%) And hexane (40-50 mol.%) Makes it possible to almost completely remove phenol and salicylic acid from aqueous solutions at 15 and 30 times concentration, respectively. test compounds directly in the extract, which makes the proposed method express.

The method allows to reduce the detection limit of the test substances compared to the known (0.005 mg / ml) 4 to 0.0001 mg / ml, i.e. more than a dock.

Claims (1)

Invention Formula - - Method for the separate determination of phenol and salicylic acid in their mixtures in aqueous solutions, including extraction with an organic solvent and photometry of the extract ,. characterized in that, in order to increase the accuracy of the determination and shorten the duration of the method, a mixture of triisobutyl phosphate and hexane is used as an organic solvent in the following ratios of components, mol%, Triisobutyl phosphate 50-60 Hexane 40-50 the extraction is carried out first at pH 7 - pH 7-9, the extract is separated, then at pH 1.5-2 photometry is subjected to each of the extracts. 1559284 ten table 2 Substance The degree of extraction depending on the pH of the aqueous solution 1.5 | 2.0 | 3.0 I 3.8 | 4.6 6.0 17.0 | 8.5 | 9.0 J10.2 | 10.8 111.6 96 96 96 96 96 96 96 95 95 89 98 98 97 90 61 Sign of Number of consecutive extractions required for practically complete (95-97%) extraction of phenol and salicylic acid Number of extractions The duration of the anaTable 3 43 34 Table 4 The proposed method 6 2 4-5