SU1617326A1 - Method of quantitative determination of polymethacrylic acid in solutions - Google Patents

Abstract

This invention relates to the field of polymer chemistry and can be used in analytical chemistry. The invention improves the detection sensitivity up to 0.006 mg and increases the detection accuracy (relative measurement error 1-4%), which is achieved by treating the sample being analyzed with an alkaline solution of phenolphthalein with a PH of 9.45-9.50, measuring the optical density of the solution at 550 nm in the presence of indifferent electrolyte NACL and the subsequent calculation of the amount of acid using a calibration curve having the formula A = 0.835-0.674X, where A is optical density, X is the amount of acid, mg. 1 tab.

Description

The invention relates to the field of polymer chemistry, namely to a method for the quantitative determination of polymethacrylic acid (PMAC) in aqueous solutions, and can be used in analytical chemistry.

The purpose of the invention is to expand the range of detectable concentrations of polymethacrylic acid and increase the accuracy of the analysis.

To ensure the linearity of the calibration curve, the sample being analyzed is treated with a chemical reagent in the presence of an indifferent electrolyte, such as NaCl.

The choice of the alkaline reagent as the most optimal pH value, as well as the use of phenolphthalein, is due to the fact that the greatest change in the color of phenolphthalein with a change in the pH of the medium is observed in the range of pH 9.1 - 9.5, which just falls on the region of the greatest slope of the titration curve of the PMAC alkali .

The calibration curve takes the form of a line in the presence of an indifferent electrolyte — NaCl, the concentration of which in the photometric solution should be at least 4–10 mol / l. This type of dependence makes it easy to find the parameters of the calibration equation using the least squares method, and therefore it is more strict to estimate the accuracy of the analysis results.

The method includes three preparatory stages (preparation of a buffer solution, a solution of flower reagent, construction, calibration curve) and the actual analysis.

Preparation of buffer solution (BR).

5 g of mansous and 2.5 Na2B4O7-10 NgO are dissolved in 900 ml of distilled water and the pH of the solution is adjusted to 9 1 by adding 0.5 mol / l of NaOH solution, the solution is brought to 1 liter and combined with CO2 removal system (pH accuracy ± 0.05).

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Preparation of color reagent solution (CR).

10 ml of a solution of 1 g of phenolphthalein brand CH.A. in 100 ml of methyl alcohol is diluted to a volume of 800 ml and 125 ml of BR buffer solution is added. The volume of the solution is brought to 1000 ml and connected to the CO2 purification system by means of a calibration curve.

In a volumetric flask with a capacity of 50 ml is placed with a pipette 0; 2.0; 4.0; 5.0; 6.0; 8.0; 10.0 ml of a standard PMAC solution containing 10 mg MPAA in 100 ml of water. After that, 5.0 ml of CR and 2.0 ml of sodium chloride solution are added to each flask, and the density of the test solution, (481) is found at the end of the optical density of the test solution, which is 0.5 mg. t-Example 2. A sample solution containing 1.00 mg PMAA was introduced into a 50 ml volumetric flask. The preparation of the sample for analysis and photometric measurement is carried out analogously to example 1. In the sample, 1.01 mg of PMAA are found.

Example 3. A sample solution containing 0.25 mg PMAA was introduced into a 50 ml volumetric flask. Preparation of samples for analysis and photometric measurements are carried out analogously to examples 1-2. In the sample are 0.25 g of PMAC. For several (5-7) parallel concentrations of 1 O mol / L, the solution is made to determine the PMAA in the solutions in tabulated labels with distilled water. For half, the results of the statistical

optical solutions of polymethacrylic acid (for

 5 cm cuvettes at 550 nm. Probability 95, and a reference solution is distilled water. Based on the numerical values of the concentration of PMAA in the solution and the corresponding values of optical density (A), a calibration curve is drawn. The equation of the calibration curve calculated by the least squares method is

, 835-0.674X, where A is the optical density;

X is the content of PMAC, mg.

The course of the analysis.

In a 50 ml volumetric flask, an aliquot portion of the test solution (1-10 ml) containing 0.1-1 mg PMMA (MM 30000) is placed, 5.0 ml CR, 2 ml i mol / l sodium chloride solution and volume the solution is made up to the mark with distilled water. The absorbance is measured in 5 cm cuvettes at 550 nm. The comparison solution is distilled water. According to the values of optical density, the amount of PMAA in the initial solution is determined using a calibration curve.

definitions, Stunt Dent ratio, 78).

2Q From the table it can be seen that the absolute detection error does not exceed 0.01 mg.

The detection limit of the proposed method, found by the third criterion, is 0.006 mg (, 95), which indicates the higher sensitivity of the proposed method.

Claims (3)

Invention Formula The method of quantitative determination of polymethacrylic acid in solutions by treating an analyzed sample of an aqueous solution of polymethacrylic acid with an alkaline reagent, measuring the optical density of the treated solution and then calculating the amount of acid in the sample, characterized in that, in order to wipe the interval of concentrations of polymethacrylic acid and an increase in the accuracy of the analysis, the determination is carried out in the presence of an indifferent electrolyte, sodium chloride, determination of polymethacrylic acid in solutions by treating an analyzed sample of an aqueous solution of polymethacrylic acid with an alkaline reagent, measuring the optical density of the treated solution, and then calculating the amount of acid in the sample, characterized in that, in order to widen the range of the concentrations to be determined polymethacrylic acid and an increase in the accuracy of the analysis, the determination is carried out in the presence of an indifferent electrolyte — sodium chloride; as an alkaline flask with a capacity of a reagent and an alkaline stretching phenolphthalein thief with a pH of 9.45-9.50, the optical density of the solution is determined spectrophotometrically by absorbance at 550 nm, the calculation of the amount of polymethacrylic acid is Example 1. 50 ml were placed 5.0 ml of the analyzed solution containing 0.50 mg of PMAC, 5.0 ml of CR and 2.0 ml of 1.0 mol / L sodium chloride solution were added. The solution is diluted to the mark with distilled-45 is carried out by formula water. After preparing the solution, 835-0.674X, The optical density of the solution in a 5 cm cuvette at 550 nm is measured. Vegan A is optical density; X is the amount of acid. The optical density of the test solution (, 481) according to the calibration graph found the content of PMAA in the sample, which was 0.5 mg. Example 2. A solution sample containing 1.00 mg PMAA is introduced into a 50 ml volumetric flask. The preparation of the sample for analysis and photometric measurement is carried out analogously to example 1. In the sample, 1.01 mg of PMAA are found. Example 3. A sample solution containing 0.25 mg PMAA is introduced into a 50 ml volumetric flask. Preparation of samples for analysis and photometric measurements are carried out analogously to examples 1-2. In the sample are 0.25 g of PMAC. For several (5-7) parallel definitions of PMAA in solutions in the table of probabilities, 95, and the multiplicity of determinations, the Student coefficient, 78). The table shows that the absolute detection error does not exceed 0.01 mg. The detection limit of the proposed method, found by the third criterion, is 0.006 mg (, 95,), which indicates a higher sensitivity of the proposed method. Invention Formula The method of quantitative determination of polymethacrylic acid in solutions by treating an analyzed sample of an aqueous solution of polymethacrylic acid with an alkaline reagent, measuring the optical density of the treated solution, and then calculating the amount of acid in the sample, characterized in that, in order to widen the interval of determined concentrations of polymethacrylate acid and increase the accuracy of the analysis, the determination is carried out in the presence of an indifferent electrolyte - sodium chloride, is used as an alkaline reagent alkaline form a stretch   carried out according to the formula, 835-0,674X, where A is optical density; X is the amount of acid. 1.00 1.00 1,, 04 1 ,, 10 5.0 ABOUT, iO, 0 1.5