RU2201780C2 - METHOD OF SEPARATELY DETERMINING α-, β-LEWISITES, THEIR OXIDES, AND CHLOROVINYLARSONIC ACIDS WHEN PRESENT IN COMMON IN SOIL - Google Patents

Abstract

FIELD: analytical methods. SUBSTANCE: method can be used when effecting environmental monitoring on chemical weapons-destruction installations. Separation of α- and β-lewisites, α- and β-lewisite oxides, and chlorovinylarsonic acids is performed in the stage when soil samples are prepared involving liquid extraction methods, and determination of amount of substance in extract is fulfilled from amount of acetylene evolving upon treatment with 30% sodium hydroxide aqueous solution. EFFECT: enabled integrated analysis of α- and β-lewisite and their degradation process products in soil. 6 cl, 3 tbl

Description

 The invention relates to the field of analytical chemistry, namely the study and analysis of materials by separation from complex matrices.

 To date, a limited number of methods are known that allow the analysis of soil samples containing lewisite and its degradation products.

 A known method for the extraction of α-lewisite and its oxide from soil samples by liquid extraction (Guide to work in the automotive radiometric and chemical laboratories AL-4, M .: Voenizdat, 1988, p. 54-57). The main disadvantage of this method is that, according to this method, α-lewisite and its oxide are extracted and determined in total.

 There is a method for the extraction of α-lewisite from acidic solutions by extraction with hexane followed by evaporation of the solvent (Stankov et al. "Chemical-chromatographic determination of β-chlorovinyl dichloroarsin in air and reaction mixtures of its processing", 1996, v.51, 5, p.528 -532). However, this method is designed to determine α-lewisite and its oxide in the reaction mass during the disposal of its reserves.

 The possibility of determining β-chlorovinylarsine oxide in soil based on fluid extraction has been shown (Decision on the grant of a patent of the Russian Federation according to application 96122963 dated December 9, 1996 “Composition of an extractant for extracting β-chlorovinylylarsine oxide from soil samples” // Alimov N.I. et al. - 12 p.). The main disadvantage of this method is the use of expensive equipment, the extraction coefficient in this case is about 50%.

 A method has been developed based on the determination of lewisite when it is extracted from the soil with a mixture of hexane-ethanol taken in a ratio of 3: 1 (by volume), respectively (Gas chromatographic determination of lewisite in soil. - Volgograd.: VNIIGTP, 1996, 25 s.) . The main disadvantage of this method is that only α-lewisite is extracted and analyzed by this method.

 The present invention was the development of a method for the separate determination of α-, β-lewisite, oxides of α-, β-lewisite and chlorovinylarboxylic acids with their joint presence in the soil.

 The problem is solved in that at the stage of preparing the soil sample, α-, β-lewisite, oxides of α-, β-lewisite and chlorvinylilarsonic acids are separated using liquid extraction techniques, and the amount of the substance in the extract is determined by the amount of acetylene released during the processing of solutions 30% aqueous sodium hydroxide solution.

 The basis of the claimed invention is the fact that, practically, all forms of lewisite and the products of its transformation contain a vinyl group. When carrying out an alkaline hydrolyzate of these substances, acetylene is released, the amount of which determines the concentration of the analyte. On the one hand, the acetylene formation reaction is highly specific to the vinyl group. In addition, this reaction can be used in the analysis both with the involvement of chemical methods (spectrophotometric) and with the use of chromatographic methods of analysis. On the other hand, this reaction is a group reaction to all forms of lewisite and almost all transformation products, which requires their preliminary separation at the stage of sample preparation.

 To separate the substances to be determined, the method of their liquid extraction from soil samples with benzene in an ultrasonic bath was used. It was shown that in this case only a mixture of α-, β-lewisites is transferred to the extractant, while their oxides and chlorvinylarboxylic acids are not recovered. The separation of α-, β-lewisites was carried out by double reextraction from benzene with 0.1 N hydrochloric acid. It was found that only α-lewisite passes into the aqueous phase, while β-lewisite remains in the organic phase. The degree of extraction of α-lewisite is 98%. The extraction of α-, β-lewisite oxides from the soil was carried out by converting them into α-, β-lewisite by treating the soil with concentrated hydrochloric acid, followed by their extraction with benzene. The separation of α- and β-lewisite was carried out in accordance with the above conditions.

 The verification of the correct determination of the micro quantities of α- and β-lewisite with their joint presence was carried out by the introduced-found method. The research results are presented in table 1.

 From the analysis of the obtained experimental studies, are given in table. 1, it follows that the developed method allows to accurately determine the microquantities of these substances against the background of a twenty-fold excess of one component relative to another.

 In the course of studying the processes of destruction of α- and β-lewisites, we found that these compounds in the soil are oxidized to chlorovinylarboxylic acids, which also have vinyl fragments. In the course of experimental studies, it was found that during ultrasonic treatment of the sample with distilled water, α-lewisite also passes into the extractant, in addition to chlorovinylarsonic acids. As a result, α-lewisite may be mistaken for chlorovinylarsonic acids. This necessitated the separation of chlorvinylarboxylic acids and α-lewisite for their subsequent selective determination.

 The extraction of chlorvinylilarsonic acids from the soil is carried out using distilled water in an ultrasonic bath.

 For the separation of chlorvinylilarsonic acids and α-lewisite, the ion exchange resin AB-17-8 (chlorine form) was used. In the course of studies, it was found that the anion exchange resin AB-17-8 completely sorb chlorvinylarsonic acids and practically does not sorb α-lewisite. The determination of chlorvinylilarsonic acids is carried out by direct processing of the anion exchange resin with a 30% aqueous solution of sodium hydroxide. Verification of the determination of chlorovinylarboxylic acids and α-lewisite was carried out by the introduced-found method.

 For this, a known amount of the analyte was added to 10.0 ml of distilled water. The test solution was passed through a glass column with anion exchange resin at a rate of 2 ml per minute. The ion-exchange resin with the sorbed substance was treated with a concentrated alkali solution and the content of 2-chlorovinylarsonic acid was determined by the amount of acetylene released. The research results are given in table.2.

 The results of experimental studies, shown in table 2, show that the developed method for the separation of chlorvinylilarsonic acids and α-lewisite can reliably distinguish the analyzed compounds when they are together in the soil. It is noted that the excess of one component in relation to another by 20 times does not affect the reliability of their quantitative determination.

 For the selective determination of the content of chlorvinylarboxylic acids in the soil, they were extracted with a 2% aqueous solution of sodium carbonate in an ultrasonic bath for 10 minutes. The weight ratio of soil to water was 1: 2, respectively. The acid content was determined by acetylene. Studies have shown that the coefficient of extraction of chlorovinylarsonic acids from soil samples is 65 ± 5%.

 In the course of the studies, it was found that the proposed separate extraction method allows a comprehensive analysis to determine the content of α-, β-lewisite and their degradation products in the soil. In accordance with this, a block diagram of the algorithm for conducting a comprehensive analysis of the soil, presented in the drawing, was developed.

 Evaluation of the performance of the proposed method for the comprehensive analysis of soil samples was carried out on an artificial mixture consisting of α-, β-lewisite, oxide α-lewisite and 2-chlorovinylarsonic acid by the introduced-found method. The research results are presented in table.3.

 Thus, the results obtained on the separation of the components of technical lewisite and its degradation products at the stage of sample preparation for quantitative chemical analysis allow us to evaluate the contribution of each component to the total soil contamination.

Claims (6)

 1. The method of separate determination of α-, β-lewisite, oxides of α-, β-lewisite and chlorovinylarsonic acids when they are together in the soil, which consists in the fact that at the stage of preparation of the soil sample, separation of α-, β-lewisite, oxides α -, β-lewisites and chlorvinylarboxylic acids using liquid extraction techniques, and the amount of the substance in the extract is determined by the amount of acetylene released during the treatment of the solutions with a 30% aqueous sodium hydroxide solution.  2. The method according to claim 1, in which the extraction of a mixture of α-, β-lewisites from the soil is carried out using liquid extraction with benzene in an ultrasonic bath, and the separation of α-, β-lewisites is carried out by double re-extraction of α-lewisite into the aqueous phase 0 , 1 N aqueous hydrochloric acid.  3. The method according to claim 1, in which the extraction of oxides of α-, β-lewisites from the soil is carried out by processing samples with concentrated hydrochloric acid to convert them to α-, β-lewisite.  4. The method according to claim 1, in which the extraction of chlorvinylilarsonic acids from the soil is carried out using distilled water in an ultrasonic bath, and the separation of chlorvinylilarsonic acids and α-lewisite is carried out on anion exchange resin AB-17-8 in chlorine form.  5. The method according to claim 1, in which the determination of chlorovinylarsonic acids is carried out by direct processing of the anion exchange resin with a 30% aqueous solution of sodium hydroxide.  6. The method according to claim 1, in which the selective extraction of chlorovinylarsonic acids from the soil is carried out using a 2% aqueous solution of sodium carbonate in an ultrasonic bath.

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