SU1578644A1 - Method of determining peroxycarboxylic acids - Google Patents

Abstract

The invention relates to analytical chemistry, in particular the determination of peroxycarboxylic acids in a mixture, which can be used in their manufacture. The goal is to increase the sensitivity of the analysis. The latter is treated by treating the initial sample with methyl morpholine or 4-hydroxyethylmorpholine at PH 7.4-7.6 in a buffer solution, followed by measuring the reaction rate by the modometric method. These conditions increase the sensitivity of the assay to 3.10 -4 mol / l, which is three times lower than the known, and reduce the duration of the assay from 120 to 35 minutes. 3 tab., 1 Il.

Description

This invention relates to analytical chemistry, in particular, to a method for the joint determination of peroxycarboxylic acids in a mixture.

The purpose of the invention is to increase the detection sensitivity, shorten the analysis time and simplify the method.

Example A sample containing 1.45 "Yu g-eq / l peroxyacid is pipetted into 15.00 ml in a 100 ml volumetric flask and diluted with a buffer mixture from pH 7.50 to nearly 90 ml. 3.5 ml of 0.1 mol / l methylmorpholine is poured in, quickly brought to the mark with distilled water and stirred, noting the time. After certain periods of time (1,3,5, 7,10,15,20,25,30 min) are taken in conical flasks of 10,00 ml aliquot

parts, add to each flask 1 ml of a 50% aqueous solution of acetic acid, 1 ml of a 5% aqueous solution of acetic acid, 1 ml of a 5% aqueous solution of potassium iodide, after which the separated iodine is titrated to 0.02 and. sodium thiosulfate solution in the presence of starch as an indicator. For control, 15.00 ml 1.45-10 n. The sample solution is poured into a 100 ml volumetric flask and diluted to the mark with a buffer mixture of pH 7.5 and stirred. The 10.00 ml aliquots selected from this solution are treated in the same manner as described above.

The drawing shows the graphs.

Build the dependence of hg {(fC) / CAJ6- - (CcJ0-C-jJ) on time, where 1

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the concentration of peroxyacids at the time C, a (A) and (C) -1, respectively, the initial concentrations of amine and peroxyacids. The linear portion of the kinetic curve with a tangent of slope corresponding to a reaction involving a peroxyacid of a lower reactivity extrapolates O (in the drawing, the ordinate axis intersects at point A). Build a direct AB parallel to the time axis. Find the time corresponding to the intersection point of this straight line with the constructed kinetic curve (point B). Then the concentration of the more reactive peroxy acid is equal to the concentration of peroxy acid that has reacted by this time. From the graphical dependence of C $ on Ј, the concentration of peroxy-acids reacted by this time is determined. The total content of peroxyacids in the sample was found in the control experiment. According to the difference between the total content of peroxy acids in the sample and the content of the more reactive peroxy acid, the content of another component of the mixture is found.

Similarly, the process is carried out using 4-hydroxyethylmorpholine as a tertiary amine. Data on the effect of pH on the determination error are given in Table. 1 and 2. As can be seen from the table. 1 and 2 at pH: 4.7.4 and pH 7.6, the relative error in the determination of peroxy acids increases significantly and exceeds the permissible value for this kinetic method. In tab. 3 shows the results of the analysis of mixtures of peroxyacids.

The smallest amount of peroxycarboxylic acid, determined by the described method with reliable accuracy is 3 10 mol / l, which is more than three times lower than that achieved in the known method, and indicates a higher sensitivity of this method compared to the known one.

An increase in the sensitivity of the determination is achieved by using for the analysis a fundamentally new reaction — the N-oxidation reaction, as well as measuring its speed by the iodometry method. Methylmorpholine or 4-hydroxyethylmorpholine as a reagent for peroxycarboxylic acids instead of diphenylaminosulfonate used in the known method,

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eliminates the heating operation, since the rate of interaction of peroxycarboxylic acids with tertiary amines is higher than with diphenylamine sulfonate, and does not require an increase in temperature; to simplify the process, since tertiary amines are completely stable in some solutions and do not require special cleaning and storage techniques; eliminate the need for calibration dependencies, which reduces the analysis time from 120 minutes to 35 minutes.

Claims (1)

The method is suitable for analyzing mixtures of various peroxycarboxylic acids and does not require the presence of pure individual components of the mixture. Claim 1: A method for determining peroxycarboxylic acids by treating an analyzed sample with an amine in a buffer solution, followed by measuring the reaction rate, characterized in that methylmorpholine or 4-hydroxyethylmorphramide is used as an amine the folin treatment of the sample is carried out at pH 7.4-7.6 and the reaction rate is measured by the iodometric method. Table 1 Influence of environmental pI on the error in the determination of peroxycaprylic acid in a mixture of peroxycapril – liperoxy adipic acid (1: 1) with methyl meorpholine pH Relative determination error,% table 2 The effect of pH on the error in the determination of peroxycaprylic acid in a mixture of peroxycapryl-peracetic acid (1: 1) with 4-g of droxyethylmorpholine PH Relative determination error,% Table 3 The results of the kinetic analysis of mixtures of peroxy acids by oxidation reactions Peroxycaprylic acid (A) -diperoxyadipic acid36,47 Peroxycarbonic acid (A) -peroacetic acid 30.25 Peroxycapryl acid (A) diperoxysebacic acid36.45 4-hydroxyethylmorpholine was used as a tertiary amine, tff CT Wff-fo-cd  ten 10.0 6,0 2,0 ten 4.8 6.25 5.1 15 20 25 30 T, m #,