SU1374118A1 - Amperometric method of quantitative determination of stable nitroxyl radicals - Google Patents

Abstract

This invention relates to the analytical chemistry of organic compounds. The purpose of the invention is to increase the sensitivity and selectivity of the determination of stable nitroxyl radicals. Amperometric titration is carried out using two indicator electrodes. The potential difference between the electrodes is not less than 0.01 V. The radical content is determined from the current formed during the titration of the redox pair of the radical-ammonium cation. The invention makes it possible to use it for the study of radical value and redox processes in biological objects. 2 tab.

Description

00

113

This invention relates to analytical organic chemistry, in particular to a method for the quantitative determination of stable nitroxyl radicals by amperometric titration.

The aim of the invention is to increase the sensitivity and selectivity of the determination.

Example. A sample containing an iminoxyl radical (rubber, polymer, etc.) is thoroughly mixed to evenly distribute the radical in the sample. A precise sample is placed in a titration beaker, 15-20 mm of an organic solvent miscible with water, for example acetone, is added and stirred on a magnetic stirrer. A small amount of acid (sulfuric, acetic or other) is poured until the solution is acidic and titrated with an oxidizing agent, for example, potassium permanganate solution, amperometrically on two indicator electrodes with a potential difference equal to or more than 0.010 V, the redox pair current is stable the radical is ammonium cation. The consumption of titrant is proportional to the number of i-inox groups. The percentage of the radical is found by the formula

V N-V-MfllOO 1000-n-m

Where

normality of the oxidizer solution, c

(CMo);

the volume of the titrating solution, the molecular weight of the radical} sample weight, g; the number of groups N-0 in the radical-Q

le.

0

five

0

c

Q

182

The determination time is 10-15 minutes. The results of determining the number of radicals are given in Table. one.

Table 2 shows the results of the determination of 2,2,6,6-tetramethyl-4-hydroxy-1-hydroxy in a butyl rubber based sealant in a mixed solvent toluene-acetone - 50% acetic acid in a ratio of 2: 1 : 2.

The proposed method makes it possible to determine (microgram (gamma) quantities of stable radicals in the presence of a number of interfering determinants, for example ascorbic, oxalic acids, iodide-ion, etc., with a relative error of about 2-3%, which makes it possible use it to radiate chain-chain and redox processes in biological objects.

Claims (1)

Invention Formula An amperometric method for the quantitative determination of stable nitroxyl radicals by titration with an oxidizing agent in acidic media, characterized in that, in order to increase the sensitivity and selectivity of the determination, titration is carried out using two indicator electrodes with a potential difference between these electrodes of at least 0.0l V and the content the radical is determined by the current formed by the radical-ammonium cation radical during the titration of the redox pair. . . Table 1 % CHj HO-QN-O SNS SNZ 17.1 17.3 1.17 12.8 12.5 2.34 8.6 8.3 3.48 in the presence of equal amounts of ascorbic acid In the presence of equal amounts of oxalic acid  V in the presence of equal amounts of potassium iodide 10,015 20,025 30,010 0.10 0.08 0.12 171 1 0.0001 0.90 0.1026 2.60 171 1 0.0001 1.20 0.0821 2.63 171 1 0.0001 0.68 0.1162 3.17 Table 2