Büro für Altlastenerkundung und Umweltforschung

Dr. Rainer Haas

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

email: haasr@gmx.net




Gas Chromatographic Determination of Chemical Warfare Agents

Gas Chromatographic Analysis of Ethylarsine dichloride by derivatization with dithiols



Rainer Haas

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



Article as pdf-file



Abstract

Ethylarsine dichloride was used during WW I as chemical warfare agent. Residues of this chemical warfare agent and its metabolites are still present today and continue to contaminate soil and water.

A gas chromatographic method for the detection and determination of ethylarsine dichloride is shown. Six dithiols were tested as possible derivatization reagents for ethylarsine dichloride. With selection of the dithiol, matrix inferences can be eliminated because of the different retention times of the derivatives.



Key words: analysis, arsenic compounds, chemical warfare agents, ethylarsine dichloride, CWA, derivatization, detection, determination, gas chromatography



1 Experimental

Ethylarsine dichloride [CAS-No.: 598-14-1] was produced in WW I as chemical warfare agent. Ethylarsine dichloride can be detected with GC/ECD without derivatization. It react with dithiols by forming cyclic derivatives, that can be detected with GC/ECD too.

Derivatizations with dithiols are performed with 1,2-ethane dithiole [Et(SH)2], 1,3-propane dithiole [Pr(SH)2], 1,4-butane dithiole [Bu(SH)2], 1,5-pentane dithiole [Pe(SH)2], 1,6-hexane dithiole [He(SH)2] and 1,8-octane dithiole [Oc(SH)2].

For the derivatization 20 µl of an acetonic dithiol solution [c=100 g/l] and 20 µl of an acetonic ethylarsine dichloride solution [c=6,8 g/l] is added to 500 µl acetone in 1,4 ml-vials (reaction time: 15 min; T = 20°C).

For the separation of ethylarsine dichloride and its dithiole 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 df 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.



2 Results and discussion

Ethylarsine dichloride react with dithiols in a substitution reaction by forming cyclic compounds:



EtAsCl2 + R(SH)2 --> EtAsS2R + 2 HCl.



The derivatization is completed in 15 min at a temperature of 20°C. The cyclic derivatives are stable. 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 ethylarsine dichloride and its dithiol derivatives is shown.

The reaction of ethylarsine dichloride with with the six tested dithiols is quantitative. After derivatization no ethylarsine dichloride can be detected with GC/ECD.

By using of 1:1 molar mixtures of two dithiols, different rates of the possible derivatives are built. This rates are presenting the thermodynamic stability of the cyclic ethylarsine dithiole derivatives. The most stable products are the derivatives of ethylarsine dichloride with 1,2-ethane dithiole and 1,3-propane dithiole. The same effect was shown by derivatization of phenylarsine dichloride (PFIFFIKUS) and 2-chlorovinylarsine dichloride (LEWISITE I) with dithiols [1,2]. All of these arsenic containing chemical warfare agents are able to form cyclic derivatives. The results are shown in table 2.

The derivatization procedure is quick and easy and the analysis is highly selective. The limits of detection differ between 1.3 ng and 3.5 ng. By choosing an appropriate dithiol, matrix interferences can be eliminated because of the different retention times of the resulting ethylarsine derivatives.

This derivatization reaction can be used for the gas chromatographic detection and determination of ethylarsine dichloride in contaminated water and soil samples together with other arsenic containing chemical warfare agents e.g. diphenylarsine chloride (CLARK I), phenylarsine dichloride (PFIFFIKUS), 2-chlorovinylarsine dichloride (LEWISITE I) and 2,2'-Dichlorodivinylarsine chloride (LEWISITE II) [1,2,3,4].



3 References

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

[2] Haas, R. (1998): Chemische Reaktionen von Chlorvinylarsinverbindungen (Lewisite). 3. Reaktion von Lewisit I und Lewisit II mit Dithiolen. UWSF-Z. Umweltchem. Ökotox. in print

[3] Haas, R. (1997): Chemische Reaktionen von Phenylarsinverbindungen. 2. Reaktion von Diphenylarsinverbindungen mit Dithiolen. UWSF Z. Umweltchem. Ökotox. 9 (1997), 123 - 124

[4] Haas, R.; Schmidt, T.C.; Steinbach, K.; v. Löw, E. (1997): Gaschromatographische Bestimmung von Arsenkampfstoffen und Umwandlungsprodukten. Fachtagung Rüstungsaltlasten (Grundwassersanierung), Munster 7./8.10.97



Table 1: Retention times (tR) and limits of detection (LOD) of ethylarsine dichloride and its dithiol derivatives; GC conditions see experimental data


thiol

derivative

tR/min

LOD/ng

---

EtAsCl2

2.84

3.5

Et(SH)2

EtAsS2Et

3.88

1.3

Pr(SH)2

EtAsS2Pr

5.48

3.5

Bu(SH)2

EtAsS2Bu

7.49

3.5

Pe(SH)2

EtAsS2Pe

12.26

3.5

He(SH)2

EtAsS2He

13.33

3.5

Oc(SH)2

EtAsS2Oc

15.77

1.7




Table 2: Rate of Ethylarsine dithiol derivatives by using equimolar mixtures of two dithiols

thiol 1

thiol 2

derivative 1

derivative 2



%

%

Et(SH)2

Pr(SH)2

97

3

Et(SH)2

Bu(SH)2

99

1

Et(SH)2

Pe(SH)2

97

3

Et(SH)2

He(SH)2

97

3

Et(SH)2

Oc(SH)2

99.5

0.5

Pr(SH)2

Bu(SH)2

87

13

Pr(SH)2

Pe(SH)2

100

0

Pr(SH)2

He(SH)2

67

33

Pr(SH)2

Oc(SH)2

81

19

Bu(SH)2

Pe(SH)2

25

75

Bu(SH)2

He(SH)2

29

71

Bu(SH)2

Oc(SH)2

36

64

Pe(SH)2

He(SH)2

56

44

Pe(SH)2

Oc(SH)2

51

49

He(SH)2

Oc(SH)2

39

61






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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