RU2215283C2 - Method of quantitatively determining hexamethylenedimaleinamide - Google Patents

Abstract

FIELD: analytical methods. SUBSTANCE: hexamethylenedimaleinamide sample solution in concentrated nitric acid is consecutively treated with 1:1 mixture of concentrated nitric and acetic acids at room temperature for 30 min and then with 20 +/- 2% sodium hydroxide solution followed by photometric analysis at 400 nm. Sensitivity of determination is 5 mcg/ml and linearity of calibration graph is fulfilled within a range of 50 to 80 mcg/ml. Determination is not hindered by substances incapable of forming salts of acid form, which are not absorbing at 400 nm. EFFECT: increased sensitivity and selectivity of determination. 2 tbl

Description

 The invention relates to analytical chemistry, and in particular to methods for the quantitative determination of hexamethylenedimaleimide (GMDM).

 A known method for the quantitative determination of dimaleinimides, which consists in their acid hydrolysis and subsequent titration of the resulting solutions with alkali [1]. The content of dimaleinimide is judged by the number of unreacted hydrolysing reagent. The disadvantages of the method include low sensitivity, the need for heating the analyzed solutions and the duration of the determinations.

 The closest in technological essence to the claimed method (prototype) is a method for the determination of dimaleinimides, which consists in the fact that the imide solution in dimethylformamide is treated with a 0.1 M potassium hydroxide solution and the resulting solution is photometric [2]. In this case, the time of determinations is reduced and the heating of the analyzed solutions is excluded, however, the sensitivity of the determinations remains insufficient.

 The essence of the invention is to increase the sensitivity and selectivity of definitions.

This goal is achieved by the fact that the GMDM sample is dissolved in concentrated nitric acid and then sequentially treated with reagents (solutions I and II), after which the resulting solution is photometered at 400 nm. Solution I is a mixture of equal volumes of concentrated nitric and acetic acids and the sample solution is treated at 20-25 ^{° C.} for 30 minutes. Next, the treatment is carried out with solution II, representing an 18-22% aqueous solution of sodium hydroxide at 20-25 ^o C. The invention is illustrated by the following examples.

Example 1. The construction of the calibration dependence for the photometric determination of GMDM. An exact portion of GMDMI (50.00 mg) was placed in a 50 ml volumetric flask and dissolved in concentrated nitric acid (density 1.38 g / cm ³ ). The resulting standard solution has a concentration of 1 mg / ml. Aliquots of not more than 1.0 ml are taken from the resulting solution, placed in graduated 25 ml tubes and 2 ml of nitrating mixture are added to each (mixture of equal volumes of concentrated nitric and acetic acids). After 30 minutes, the contents of the tubes are neutralized and adjusted to a volume of 20 ml with an 18-22% aqueous NaOH solution. The resulting solutions were photometered at 400 nm on a KFK-2 photoelectrocolorimeter in 2 cm glass cuvettes relative to a blank test solution. According to the obtained data, the equation of the calibration graph is calculated, which is shown in table 1. Some metrological characteristics of the determination of GMDM are also given there.

 Example 2. Determination of GMDM in a control sample. A sample of a GMDM sample of about 50.00 mg is dissolved in a 50.0 ml volumetric flask in concentrated nitric acid. Three series of five aliquots in graduated tubes are selected from the resulting solution. Then, 2 ml of the nitrating mixture is poured into each tube, and after operations similar to constructing a calibration graph (Example 1), the optical density of the obtained solutions is measured at 400 nm. By the value of the measured optical density, using the equation of the calibration graph and taking into account the dilution, find the content of GMDM in the sample. The results of the analysis of control samples GMDM are shown in table 2.

 Upon dissolution of GMDM samples in concentrated nitric acid, its hydrolysis occurs with the formation of maleic acid amide. The hydrolysis product undergoes intubation and becomes able to form a bright yellow salt of the aciform, which has a maximum absorption spectrum at 400 nm, in an alkaline medium. The molar absorption coefficient of the obtained colored product is 3230 ± 60, which provides a higher sensitivity for determining GMDM compared to the prototype (an order of magnitude). The range of determined concentrations of GMDM is in the range from 5.0 to 80.0 μg / ml. The relative standard deviation is of the order of 0.012-0.023.

 The determination of GMDM can be carried out in the presence of substances that do not form salts of the aciform. This increases the selectivity of the definitions.

Sources of information
1. Didenko PO, Neshel E.P. Determination of the main substance in the production of maleimides. Methods of analysis of chemical reagents and preparations. Vol. 15. - M .: IREA. 1968.S. 160.

 2. USSR author's certificate N 1506336. BI 33. S. 206.

Claims (1)

A method for the quantitative determination of hexamethylenedimaleinimide by treating a sample solution in concentrated acids with subsequent measurement of the optical density of the resulting solution at 400 nm, characterized in that the reagents use a solution of a mixture of concentrated nitric and acetic acids 1: 1 (solution I) and 18-22% - aqueous sodium hydroxide solution (solution II), and the sample solution is treated at a temperature of 20-25 ^{° C.} first with solution I for 30 minutes, and then with solution II.

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