SU1626133A1 - Method of analysis of two single-base aliphatic peroxy acids in mixture - Google Patents

Abstract

This invention relates to analytical chemistry, in particular, to the determination of two monobasic aliphatic peroxy acids in a mixture. The goal is to reduce the detection time and increase the sensitivity of the method. The definition includes treating an aliquot of the sample being analyzed with a reagent and calculating the separate content of peroxyacids. The determination of the total peroxyacid content is carried out in the first aliquot by iodometrically and the separate determination of the hydroxyacids is carried out by adding an alkaline solution of luminol to the second aliquot of the sample at pH 7.80–10.20 and then measuring the chemiluminescence and calculating the separate content of peroxyacids. The method allows separately to determine the two higher aliphatic monobasic peroxyacids in dilute solutions 5 (i.e., the sensitivity is 1.0-1.5 times higher than the known method) in 20-25 minutes. 4 tab. cl

Description

This invention relates to analytical chemistry, and specifically to methods for the quantitative determination of two monobasic aliphatic peroxy acids of Cg-Cis in a mixture.

The purpose of the invention is to reduce the detection time and increase the sensitivity in the method.

The method is carried out as follows.

1. Construction of a calibration graph for determining the total peroxy acid content.

Into a series of 50.0 ml volumetric flasks, 5 ml of glacial acetic acid, 4-5 drops of a saturated solution of potassium iodide and

2.0; 40; 6.0; 8.0 and 10.0 ml, respectively, of 1-10 M peroxycaric acid solution. The water is adjusted to the mark and after 5-10 minutes the optical density is measured on FEC-56 M at mf. No. 4 (thickness of the absorbing layer 3 cm). According to the data, a calibration graph of the dependence A f (Csum) is constructed, where A is the optical density; Csum is the number of equivalents of peroxyacid, displacing the equivalent amount of iodine, equiv. / 50 ml. The total number of equivalents of peroxyacids is determined by schedule.

2, Construction of calibration graphs of the amount of luminescence on the concentration of peroxyacids.

about go about

with

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In 25.0 ml volumetric flasks, a series of standard ethanol solutions of the corresponding peroxyacids is prepared in a concentration range of 5 10 -1 10 M. Then, 1.0 ml of a 1 M lyuminol alkaline solution, 5.0 ml of an appropriate borate buffer solution are added to the cuvette ( pH is determined according to p. 3). 1 ml of 1 M solution of Trilon B (to bind trace metals of variable valence) and 2.0 ml of double distilled water. A cuvette is placed over the cathode of the photomultiplier, the shutter is opened, 1.0 ml of the previously prepared standard peroxy-acid solution is poured in and the amount of light is measured in 1 minute. According to the data, the amount of light — the number of the introduced peroxyacid equivalents — is plotted. Using the method of least squares, we find the coefficients an and b.

linear equations

an + bp Cn where

cn is the number of peroxy acid equivalents.

3. Determination of the pH value of the experimental conditions.

The separate determination of peroxyacids is based on the different chemiluminescent activity of them in the reaction with luminol. The pH value significantly influences the amount of light emitted. It was established that the additivity condition for the sum of the light emitted during the oxidation of luminol with a mixture of two peroxyacids of v .. pKi + pK2.,

Filled with where rm and

pK2 negative logarithms of the acid constants of the corresponding peroxyacids (pH 7.80-10.20).

If the pKi and pK2 values are unknown, then the pH value is determined as follows.

At several pH values in the range of 8.0-10.0, the sum of the light emitted per 1 minute is determined by oxidation of a 10 M solution of luminol with 1 M solutions of peroxyacids included in the mixture being analyzed, and the amount of light selected during the oxidation of luminol with a mixture of peroxy acids prepared by mixing 1 10 M solutions of two peroxy acids in a volume ratio of 1: 1. According to the experiment, a graph of DC f (pH) is plotted,

w AX-ЈyM- (S, + 2y: Јum-sum of the selected light for 1 min during oxidation

0

five

0

five

a mixture of peroxyacids and amounts

the selected light during the oxidation of each peroxyacid. The resulting curve passes through the abscissa axis at the desired point.

4. Analysis of a mixture consisting of two peroxyacids.

According to claim 1, determine the total amount of CCO peroxyacids in the analyzed solution.

To determine the two peroxyacids in their mixture, two calibration schedules for each peroxy acid in the coordinates of the sum of the selected light — the initial number of equivalents of the peroxy acid taken for the reaction and the least squares method are used to determine their analytical functions.

Next, the amount of light is measured in 1 min according to p. 2 with the difference that instead of 1 ml of the standard peroxyacid solution, 1 ml of the mixture solution under study is injected.

Having obtained the necessary data, they solve the system of equations:

 2, ai + bi Ci: 32 + b2 C2;

em

Ssum

Have

msum

Hence, C2 is calculated by the formula

G Um- (a1 + E2) -l1 -C U 202 - b1

C1 Ssum-C2.

where Ci and C2 are the number of equivalents of peroxyacids;

ai, 32, bi, b2 - coefficients entering

in the equation of the linear dependence of G on the concentration of each peroxyacid:

Csum - the total number of equivalents of peroxyacids in the analyzed solution;

Ј sum - the amount of light emitted during the oxidation of luminol with a mixture of peroxyacids, rel. units

PRI me R 1. Analysis of a mixture consisting of peroxitridecanoic (C12H2 $ SOZH) and peroxikaprinovoy (CbIyOsosN) acids. The determination is carried out according to claims 1-4.

Calibration graphs of the amount of light emitted from the concentration of individual peroxyacids are described by the equations

Xu: 2) g 30+ ° 46 1 ° 9 C1;

 46- 10y

Ci3: 100 + 1.09 109-C2;

 02 1.09 109

where Ci and C2 is the number of equivalents of each peroxy acid in 1 ml of the analyzed solutions.

For a model mixture containing 1.60 eq / ml of Xu and 2.2-eq / ml of Ci3, it was found according to the calibration graph, constructed according to item 1, that the total content is -7

Peroxide Acid is 3.78 10 eq / ml. By item 4 determine the sum of the selected light

Number 395 rated units.).

The system of equations is Ci + C2 3.78 -10 7; 2, -30+ 0.46109Ci; 100+

+ 1,09109.С2; .

Solve the system of equations for C2

X.VM (a1 + ar) Ssum

C2 Sum

2b2-b1

 395 - (- 30 + 100) - 0.46 109 3.78 107

1.09 109 -0.46 MO9 -2.40 10-7 eq / ml,

Ci C sum - C2 - 3.78, 40 1.38 -10 7 eq / ml

or is it equal to:

Ci Esu Vo6 TsuvT

- 7

15

20

25

thirty

35

 1.38-10 -93.5-25 3 | 23 .ш - “

40

C2 ES13 Vo6

mci3 2, 40 10 7 -115 -25

 6.90 -10 45

ten

15

0

five

0

five

0

five

The results of the determinations are given in table. one.

Similar calculations were performed for different cases. The results of the determination are given in table. 2

Table 3 shows the choice of the pH value at which the additivity condition of the sum of the selected light is met (CH2L-1 X 4 M, Cc10: Cpc 5 M.

EXAMPLE 2 Analysis of a mixture consisting of peroxymyristic (C 1 H 2 SO 3 H) and peroxypelargonic () acids. The determination is carried out according to Example 1 with the difference that peroxymyristic and peroxypelargonic are taken instead of peroxitridecanoic and peroxycaprinic acids.

The proposed method makes it possible to separately determine the two higher aliphatic monobasic peroxy acids in dilute 5 M solutions, i.e. sensitivity is 1.0–1.5 times higher than that of the known method in 20–25 min (according to the known method 40–45 min).

Claims (1)

Invention Formula A method for determining two monobasic aliphatic peroxyacids in a mixture, including treating an aliquot of the analyzed sample with a reagent and calculating the separate content of peroxyacids, characterized in that, in order to reduce the time of determination and increase the sensitivity of the method, the total content of peroxyacids is determined iodometrically and separately determined peroxyacids are added to the second aliquot of the sample to be analyzed an alkaline solution of luminol at pH 7.80–10.20, with the following measurement of chemiluminescence and calculation of the separate peroxyacid content. pH 8.95. n 5, p 0.95 Note. Relative error of determination is 1.6-8.9% table 2 SP Yu SP with so Note. Relative error of determination is 1.8-7.5%. four about Yu about with so