Büro für Altlastenerkundung und Umweltforschung

Dr. Rainer Haas

Stadtwaldstr. 45a, D-35037 Marburg, Tel.: 06421/93084, Fax: 06421/93073

email: haasr@gmx.net

Determination of Chemical Warfare Agents

Gas Chromatographic analysis of Chlorovinylarsines (Lewisite) and their metabolites by derivatization with thiols

Rainer Haas

Büro für Altlastenerkundung und Umweltforschung, Stadtwaldstr. 45a, D-35037 Marburg

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Abstract

Chlorovinylarines (Lewisites) are produced and handled during WW I and WW II as chemical warfare agents. Residues of this CWA and their metabolites are still present today and continue to contaminate soil and water.

A gas chromatographic method for the detection and determination of Chlorovinylarsines (Lewisites) and their metabolites is shown. Lewisite II and Lewisite III, but not Lewisite I and its metabolites and the metabolites of Lewisite II can be detected and determined with GC/ECD. After derivatization with thiols the sum of Lewisite I resp. Lewisite II and their metabolites are detected. With selection of the thiol, matrix inferences can be eliminated because of the different retention times of the derivatives.

Key words: analysis, arsenic compounds, chemical warfare agents, chlorovinylarsines, cwa, derivatization, detection, determination, gas chromatography, lewisite

1 Introduction

2-Chlorovinylarsine dichloride (Lewisite 1) was produced in WW I and WW II as chemical warfare agent by Friedel Craft's alkylation of arsenic(III)chloride with ethine. During this production process the byproducts 2,2'-Dichlorodivinylarsine chloride (Lewisite II) and 2,2',2''-Trichlorotrivinylarsine (Lewisite III) are built. A mixture of these Chlorovinylarsine compounds was filled into CWA munition [1]. Old CWA munition continue to contaminate soil and water still today. Sometimes the original CWA are hydrolysed or oxidized. This metabolites cannot be detected and determined with gas chromatographic analysis. After derivatization with thiols, the metabolites can be identified and determined with gas chromatography and ECD detector.

2 Experimental

Lewisite II and Lewisite III, but not Lewisite I, can be detected with GC/ECD without derivatization. For the gas chromatographic detection of Lewisite I and the hydrolysis and oxidation products of Lewisite I and Lewisite II a derivatization procedure is necessary. Lewisite I and its metabolites react with thiols by forming 2-Chlorovinylarsine dithioether, Lewisite II and its metabolites react with thiols by forming 2,2'-Dichlorodivinylarsine thioether.

For the derivatization 20 µl of a thiol solution (c=40 g/l) in acetone is added to 500 µl of an acetonic Lewisite solution (reaction time: 15 min; T = 20°C).

In analogy to the reactions of phenylarsenic compounds [2,3,4], oxidation products of Lewisite I and II should be reduced in the first reaction step to the corresponding As(III) compounds, while the thiols are oxidized to disulfides.

Derivatizations are performed with 1-ethane thiole [EtSH], 1-propane thiole [PrSH], thioglycolic acid methyl ether [TGM] and thioglycolic acid ethyl ether [TGE].

For the separation of the lewisites and their derivatives a HP 5890 gas chromatograph with HP 7673 autosampler and electon capture detector (ECD) was used. The temperatures of the injector block and the detector were 250°C and 300°C. The injection volume was 1 µl (split injection). A DB 5 column, 30 m, 0.25 mm i.d., 0.25 mm d_f was used. The carrier gas was nitrogen (head pressure 100 kpa). The column temperature was started at 100°C (1 min), was raised with 10°C/min to 230°C and then held for another 6 min.

3 Results and discussion

2-Chlorovinylarsine dichloride (Lewisite I) react with thiols in a substitution reaction by forming 2-Chlorovinylarsine dithioether:

Cl(CH=CH)AsCl₂ + 2 RSH --> Cl(CH=CH)As(SR)₂ + 2 HCl.

2,2'-Dichlorodivinylarsine (Lewisite II) react with thiols in a substitution reaction by forming 2,2'-Dichlorodivinylarsine thioether:

[Cl(CH=CH)]₂AsCl + RSH --> [Cl(CH=CH)]₂AsSR + HCl.

The derivatives can be detected with GC/ECD. They were identified with mass spectrometry. In Table 1 the retention times and the limits of detection of the Lewisites and their thiol derivatives is shown.

2,2',2''-Trichlorotrivinylarsine (Lewisite III) does not react with thiols. It can be determined highly sensitive with GC/ECD without derivatization (see Table 1).

The reaction of Lewisite II with the four tested thiols is quantitative. The derivatization is completed in 15 min at a temperature of 20°C. After derivatization, the sum of Lewisite I and its metabolites resp. Lewisite II and its metabolites is detected. These derivatives are more stable than other reaction products. e.g. hydrolysis products or ether [5,6].

The derivatives are stable. This derivatization reaction can be used for the gas chromatographic detection and determination of Lewisites and their metabolites in contaminated water and soil samples.

The derivatization procedure is quick and easy and the analysis is highly selective. By choosing an appropriate thiol, matrix interferences can be eliminated because of the different retention times of the resulting thioether.

4 References

[1] Franke, S., Koehler, K.F., Zaddach, H. (1994): Chemie der Kampfstoffe. Munster

[2] Haas, R. (1996): Blaukreuzkampfstoffe. Chemisches Verhalten und humantoxikologische Bedeutung von Diphenylarsinverbindungen. 1. Chemische Reaktionen. Umweltmed. Forsch. Prax. 1, 183-189

[3] Haas, R., Schmidt, T.C. (1997): Chemische Reaktionen von Phenylarsinverbindungen. 3. Reaktion von Phenyl-Arsen-Verbindungen mit Dithiolen. UWSF-Z. Umweltchem. Ökotox. 9, 183-184

[4] Haas, R., Krippendorf, A. (1997): Determination of Chemical Warfare Agents in Soil and material Samples. Gas Chromatographic Analysis of Phenylarsenic Compounds (Sternutators) (1st Communication). ESPR-Environ. Sci. & Poll. Res. 4, 123-124

[5] Haas, R., Krippendorf, A., Steinbach, K. (1997): Chemische Reaktionen von Chlorvinylarsinverbindungen (Lewisite). 1. Reaktion von 2,2'-Dichlordivinylarsinchlorid (Lewisit II) mit Alkoholen. UWSF-Z.Umweltchem. Ökotox. in print

[6] Haas, R., Krippendorf, A. (1998): Chemische Reaktionen von Chlorvinylarsinverbindungen (Lewisite). 2. Reaktion von 2-Chlorvinylarsindichlorid (Lewisit I) mit Alkoholen. UWSF-Z.Umweltchem. Ökotox. in print

Table 1: Retention times (t_R) and limits of detection (LOD) of Lewisites and their thiol derivatives; GC conditions see experimental data; L1: Cl(CH=CH)As; L2: [Cl(CH=CH)]₂As

For more informations call the author by email (haasr@gmx.net)

This text was published in ESPR-Environmental Science & Pollution resarch; editors: ecomed-Verlag, Rudolf-Diesel-Str. 3, D-86899 Landsberg (http://www.ecomed.de/journals.htm).

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