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 in soil and material samples

1. Gas chromatographic analysis of phenylarsenic compounds (sternutators)



Rainer Haas1, Alfred Krippendorf2



1: Büro für Altlastenerkundung und Umweltforschung, Stadtwaldstrasse 45a, D-35037 Marburg

2: Hazard Control GmbH, Versuchsfeld Trauen, D-29328 Faßberg



Abstract

A gas chromatographic method for the determination of phenylarsenic compounds (sternutators) and their metabolites in soil and material samples is described. The chemical warfare agents (CWA), but not their hydrolysis and oxidation products, can be detected with GC/ECD. After derivatization with thiols or dithiols the sum of diphenylarsenic resp. phenylarsenic compounds can be determined with GC/ECD.

The comparison of the analytical results with and without derivatization shows that the sternutators in the investigated samples are partly metabolized.



Key words: analysis, chemical warfare agents, CWA, derivatization, gas chromatography, phenylarsenic compounds, sternutators



1 Introduction

Arsenical containing chemical warfare agents (CWA) were produced and handled in large amounts during the World Wars I and II. The former production plants and filling stations were destroyed after WW II. Residues of the CWA and their hydrolysis and oxidation products are still present today and contaminate soil and water [1].

The most important arsenic containing CWA were (german synonyms in brackets): diphenylarsine chloride (CLARK I) [Ph2AsCl], diphenylarsine cyanide (CLARK II), phenylarsine dichloride (PFIFFIKUS) [PhAsCl2] and arsine oil, a technical mixture of 5% arsenic(III)chloride, 50% PFIFFIKUS, 35% CLARK I and 5% triphenyl arsine. The arsine oil was used in mixtures with 2,2'-dichlorodiethylsufide (sulfur mustard) [2].

In this paper the gas chromatographic determination of CLARK I and PFIFFIKUS and their metabolites in soil and material samples is described. In a following paper the analysis of other CWA (resp. tabun, sulfur mustard, lewisites and their byproducts and metabolites) in soil and material samples will be described.



2 Experimental

Phenylarsenic and diphenylarsenic compounds react with methanol by forming phenylarsine ether [3,4], but they don't react with acetone.

1 g resp. 10 g of the soil or material sample is extracted 15 min with 20 ml acetone in an ultrasonic bath. The soil samples S1 and S2 were extracted three times and the recovery rates were determined assuming 100% recovery rate as the third extraction. Recovery rates exceeded 90% in the first extraction step [5] (see table 1), therefore only one extraction step is necessary. The described acetone extraction can also be used for the analysis of tabun, sulfur mustard, lewisites and their byproducts.

The CWA PFIFFIKUS and CLARK I can be detected with GC/ECD. For the gas chromatographic detection of the hydrolysis and oxidation products a derivatization procedure is necessary.

For the derivatization of the phenylarsenic and diphenylarsenic compounds and their oxidation products 20 µl of a thiol or dithiol solution (c=40 g/l) in acetone is added to 500 µl acetone extract of the soil or material sample (reaction time: 30 min). Phenylarsonic resp. diphenylarsonic compounds are reduced in the first reaction step to phenylarsenic resp. diphenylarsenic compounds, the thiols and dithiols are oxidized to disulfides.

Phenylarsenic compounds react with dithiols by forming stable cyclic derivatives [PhAsS2R]. Six dithiols were tested. The most stable derivatives are formed with 1,2-ethane dithiole [Et(SH)2] and 1,3-propane dithiole [Pr(SH)2] [6].

Diphenylarsenic compounds react with thiols by forming diphenylarsine thioether [Ph2AsSR]. Derivatizations are done with 1-ethane thiole [EtSH] and 1-propane thiole [PrSH] [7].

For the separation of the sternutators and the 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 resp. 5 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.



3 Results and discussion

The following reduction rates with thiols are determined with reference compounds (in comparison to PFIFFIKUS and CLARK I) [5]:

* phenyl arsonic acid (oxidation/hydrolysis product of PFIFFIKUS): with Et(SH)2 31,5% and with Pr(SH)2 55,2%

* phenylarsine oxide (hydrolysis product of PFIFFIKUS): with Et(SH)2 and Pr(SH)2 100%

* diphenyl arsonic acid (oxidation/hydrolysis product of CLARK I): with EtSH 81,3% and with PrSH 94,5%

* bis(diphenylarsine) oxide (hydrolysis product of CLARK I): with EtSH 80,3% and with PrSH 100%.

After derivatization with dithiols resp. thiols the sum of phenylarsenic resp. diphenylarsenic compounds and their oxidation and hydrolysis products is detected. The thiol derivatives are more stable than other reaction products, e.g. ethers [3,4].

The derivatization procedure is quick and easy. With choosing an appropriate thiol or dithiol, matrix inferences can be eliminated, because of the different retention times of the various thiol derivatives (see table 1). Due to the derivatization the analysis is highly selective.

Two soil samples (S1, S2) and three material samples from former CW munition (M1, M2, M3) were investigated. The normalized results are shown in table 2. The comparison of the normalized concentrations of the CWA with and without derivatization shows that a considerable amount of the CWA in these samples are hydrolized and/or oxidized.

The comparison of the analysis with and without derivatization allows to determine the rate of metabolization. In table 2 it is shown that the concentrations of PFIFFIKUS, CLARK I and the sum of phenylarsenic resp. diphenylarsenic compounds (after derivatization) differ up to a factor of 3, therefore derivatization is necessary for the examination of environmental samples.



4 References

[1]: Office of the chief of chemical corps, headquaters european command: The history of captured enemy toxic munitions in the american zone, european theater May 1945 to June 1947

[2]: Kopecz, P. (1996): Review of Suspected Warfare-Related Environmental Damage in the Federal Republic of Germany. Part 3: Chemical agents dictionary. UBA-Texte 32/96. Berlin, Umweltbundesamt

[3]: Haas, R. (1996): Chemische Reaktionen von Phenylarsinverbindungen. 1. Umsetzung mit Alkoholen zu Diphenylarsinether. UWSF-Z. Umweltchem. Ökotox. 8, 183

[4] Haas, R.; Krippendorf, A.; Steinbach, K. (1997): Chemische Reaktionen von Phenyl-Arsen-Verbindungen. 4. Reaktion von Phenylarsindichlorid (Pfiffikus) mit Alkoholen. UWSF-Z. Umweltchem. Ökotox. 9, in print

[5] 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, in print

[6] 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

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




Table 1: Retention times (tR), limits of detection (LOD) and recovery rate of arsenic containing CWA and their derivatives; GC conditions see experimental



compound


thiole

tR

LOD

recovery rate





min

ng

%


PhAsCl2


---

7,79

4,0

98


PhAsCl2


Et(SH)2

13,95

0,1

92


PhAsCl2


Pr(SH)2

15,45

0,2

92


Ph2AsCl


---

13,77

0,6

93


Ph2AsCl


EtSH

16,21

0,6

94


Ph2AsCl


PrSH

17,44

0,6

94





Table 2: Normalized concentrations of CLARK I [Ph2AsCl] and PFIFFIKUS [PhAsCl2] with and without derivatization in soil (S1, S2) and material samples (M1, M2, M3)


compound

S1

S2

M1

M2

M3

PhAsCl2

1

1

1

1

1

PhAsS2Et

1,80

0,56*

3,40

2,63

1,34

PhAsS2Pr

2,11

1,31

2,93

3,05

1,25

Ph2AsCl

1

1

1

1

1

Ph2AsSEt

2,00

2,21

3,21

1,16

1,02

Ph2AsSPr

2,33

2,30

2,73

1,20

1,07


*: matrix inference







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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