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© Springer-Verlag Berlin Heidelberg 2005 II.8.1 Sarin and its decomposition products by Hiroaki Ando and Yoshihiko Miyata Introduction Chemical weapons chemical warfare agents, such

© Springer-Verlag Berlin Heidelberg 2005

II.8.1 Sarin and its

decomposition products

by Hiroaki Ando and Yoshihiko Miyata

Introduction

Chemical weapons ( chemical warfare agents), such as sarin and soman, were developed to kill

or injure humans by their toxic actions Th ey are called “ nuclear weapon of the poor”, because the weapons are relatively stable during storage, cheap for production and relatively easily synthesized with basic knowledge on organic chemistry Main advanced countries are making eff orts to reduce chemical weapons existing in the world on the basis of the Chemical Weapons Convention ( CWC), aft er the Iran-Iraq War and the Gulf War In 1990, an incident of human injury using mustard (yperite) took place at a usual residence at Komagome, Tokyo In 1994 and 1995, unprecedented sarin poisoning terrorism took place in Matsumoto and Tokyo, Japan and surprised the whole world in the fear that similar chemical terrorism would be reproduced

in other countries Also in 1994, an attorney-at-low and his family were killed using VX in Osaka, Japan Th e above sarin and VX incidents were found committed by the same cult group

Th ese incidents show that chemical weapons can be used not only for wars, but also can be convenient means of crimes

To cope with such crimes using chemical weapons, such as yperite and sarin, various pre-ventive measures should be taken on the basis of the Revised Poisonous and Deleterious Sub-stances Control Law and the Chemical Weapons Banning Law of Japan; when such an incident happens, proper and rapid actions should be taken to minimize the damages

In the list of scheduled chemicals being defi ned by CWC, there are toxic chemicals and precursors for each of Schedules 1–3 In this chapter the word “chemicals” is used for such scheduled chemicals for simplicity Before analysis of the chemicals, it is essential to get to know their histories, methods of synthesis, properties, directions for use, toxicities, therapeutic methods, stabilities and analytical methods

Th e chemicals directly act on organisms (animals and plants) and exert their toxicities; they are classifi ed into the following 3 groups [1, 2]:

• Poisonous chemicalsa: they directly exert toxic eff ects and kill or injure humans and animals

• Incapacitating chemicals: they neither cause severe injuries nor fatalities, but incapacitate people temporarily

• Chemicals for plants: they are used as defoliants using their herbicidal action

In this chapter, the methods for qualitative analysis of sarin and its decomposition products, which the authors experienced, are presented [3–6] Th e chemical name of sarin is

methyl-phosphonofl uoridic acid isopropyl ester or O-isopropylmethylmethyl-phosphonofl uoridate (US code:

GB, CAS registration No.: 107-44-8)

Sarin is an unstable compound and easily decomposed into nonpoisonous isopropylmethyl-phosphonic acid, followed by further decomposition into methylisopropylmethyl-phosphonic acid b Th e above

two products stably exist in soils and water for relatively a long period around the spot, where sarin has been sprayed; if isopropyl methyl phosphonic acid is identifi ed, it can be verifi ed that sarin has been used

Reagents and specimens

• Sarin: a plastic bag containing about 600 mL of light-brown fl uid, which had been obtained

at Kasumigaseki Station of the Chiyoda subway line, was carefully opened, and used as the original specimen of sarin

• VX: the compound hidden by a cult group and seized by police was used

• Other compounds: N,N-diethylaniline ( DEA), trimethyl phosphate, methylphosphonic acid, dimethyl methylphosphonate, methyl phosphonic dichloride, acetonitrile-d3, deuterated

chlo-roform (CDCl3), diisopropyl phosphorofl uoridate ( DFP) and N-methyl-N-(tert-butyl-dimeth-ylsilyl)trifl uoroacetamide (MTBSTFA) can be all purchased from Aldrich (Milwaukee, WI, USA); triisopropyl phosphate, isopropyl hydrogenmethylphosphonate and diisopropyl methyl-phosphonate were synthesized in our laboratories according to the literature [7]

GC/MS analysis

GC/MS conditions

GC column: an HP-5MS fused silica capillary column (30 m × 0.25 mm i.d., fi lm thickness 0.25 µm, Agilent Technologies, Palo Alto, CA, USA)

GC/MS conditions; injection temperature: 250 °C; injection pressure: 1.05 kg/cm2; column (oven) temperature: 50 °C (2 min) → 20 °C/min → 250 °C (10 min); carrier gas: He (13 psi); split ratio, 50; ion source temperature: 250 °C; EI electron energy: 70 eV; CI mode reagent gas: isobutanec; CI electron energy: 230 eV; ionization current: 300 µA

Procedure

i Direct analysis

A part of the original sarin specimen solution is diluted 10–50 fold with hexane (or acetone) and injected into GC/MS

ii Analysis of decomposition products

i About 1 g of the above original sarin specimen solution is mixed with 12 mL of 5 % KOH solution, and left for about 24 h at room temperature Using the headspace vapor of the mixture, the absence of undecomposed sarin is confi rmed by GC/MS

ii Th e above aqueous solution is extracted with chloroform (30 mL × 3 times)

iii Aft er each centrifugation, the chloroform layers are combined, and dehydrated with anhy-drous Na2SO4; the clear supernatant chloroform extract is condensed under reduced pres-sure (sample A)

iv Th e aqueous layer is also condensed under reduced pressure (sample B).

v Parts of the samples A and B are placed in screw-cap glass vials respectively, and equally evaporated to dryness under streams of nitrogen Each residue is mixed with 30 µL aceto-nitrile and 30 µL MTBSTFA, heated at 60 °C for 1 h for tert-butyldimethylsilyl (TBDMS)

derivatization and injected into GC/MS

Assessment of the method

> Figure 1.1 shows a TIC obtained by GC/MS for the diluted original sarin specimen

ob-tained from the Tokyo Subway Sarin Incident By measuring mass spectra and retention times, the peaks except for sarin were identifi ed as DFP, diisopropyl methylphosphonate, triiso propyl phosphate and DEA

Th e big peak appearing at the retention time of 4 min in > Figure 1.1 is due to sarin Th e

EI and CI mass spectra of sarin are shown in > Figures 1.2 and 1.3, respectively In the EI

mass spectrum, no molecular peak (m/z 140) appeared; but a peak of the desmethylated form appeared at m/z 125.

> Figure 1.4 shows a TIC and EI mass spectra for two peaks appearing in the TIC Peaks 1

and 2 correspond to TBDMS derivatives of isopropyl methyl phosphonic acid and methylphos-phonic acid, respectively For both compounds, neither molecular nor quasi-molecular peak appears In the CI mode, both compounds showed the base peaks of their protonated molecular

ions at m/z 252 and 325, respectively.

In this connection, > Figure 1.5 shows an EI mass spectrum of underivatized VX No

molecular peak (m/z 267) appeared; a fragment ion at m/z 114 was the base peak > Figure 1.6

TIC by GC/MS for the original sarin specimen obtained at the Tokyo Subway Sarin Incident.

⊡ Figure 1.1

EI mass spectrum of sarin.

⊡ Figure 1.2

CI mass spectrum of sarin.

⊡ Figure 1.3

TIC and mass spectra for Peaks 1 and 2 obtained by GC/MS for TBDMS derivatives of hydrolyzed products of sarin.

⊡ Figure 1.4

⊡ Figure 1.5

EI mass spectrum of VX.

shows a CI mass spectrum of VX; an intence protonated peak appeared at m/z 268 together with fragment peaks at m/z 252, 128 and 114.

NMR analysis

NMR conditions

i NMR instruments

JNM-EX270 and JNM-EX90A (with the tunable module) FT-NMR spectrometers (JEOL, Tokyo, Japan) were used

ii Analytical conditions

A sample tube with 5 mm i d was used For 13C, the 1H decoupling mode was employed; for 19F, the 1H non-decoupling mode; and for 31P, both 1H decoupling and non-decoupling modes

Th e conditions for the JNM-EX270 instrument were: measurement frequency, 109 MHz; mode, 1H decoupling; data points, 32 K; pulse width, 6.9 µs; pulse delay time, 5 s; integration times, 4; measurement temperature, 25 °C; and spectral width for chemical shift s, 40,000 Hz

Th e parameters for NMR measurements using the JNM-EX90A instrument are summa-rized in > Table 1.1.

CI mass spectrum of VX.

⊡ Figure 1.6

• For direct NMR analysis, the original sarin specimen was diluted with acetonitrile-d3,

placed and sealed in the sample tube for NMR measurements using the JNM-EX270 instrument

• Th e original sarin specimen was purifi ed by vacuum distillation A major fraction distilled

at 60–61 °C/25 mm Hg was collected and diluted with deuterated chloroform (CDCl3) to make solution at 95 mg/g Th e NMR measurements were carried out on the JNM-EX 90A instrument

Assessment of the method

> Figure 1.7 shows a 31P-NMR spectrum obtained from the original sarin specimen Th e main doublet signals were judged due to sarin, because they (δ:29.62 ppm, JPF = 1037 Hz)

were almost identical with those of sarin (δ: 28.44 ppm, JPF = 1046.3 Hz) reported in literature

DFP and diisopropyl methylphosphonate could be detected together with sarin by GC/MS

(> Figure 1.1); in this NMR spectrum, hydrogen methylphosphonofl uoridate appears in

ad-dition (> Figure 1.7).

Th e 1H-, 13C-, 31P- and 19F-NMR data for the purifi ed sample aft er distillation are shown

in > Table 1.2; the 31P-NMR data for decomposition products and by-products of sarin shown

in > Table 1.3.

Th e composition of sarin and contaminants in the original specimen solution of the Tokyo Subway Sarin Incident was carefully examined by 31P-NMR, using trimethyl phosphate as a standard, because it did not overlap any sarin-related compound Th e results were (w/w): sarin,

35 %; hydrogen methylphosphonofl uoridated, 10 %; diisopropyl methylphosphonatee, 1 %; and

⊡ Table 1.1

Parameters for NMR measurements of sarin

Measurement frequency

(MHz)

d internal

external

tetramethyl-silane (TMS)

TMS

trifluoroacetic acid

(δF= –76.5 ppm)

85 % phos-phoric acid measurement temperature 26 °C

(45° pulse)

3.5 µs (45° pulse)

14.5 µs (90° pulse)

12.6 µs (90° pulse) integration time

(repetition time)

32 (7 µs)

2,400 (3 µs)

64 (3 µs)

256 (5 µs)

DFP, trace (0.1 %) Th e content (w/w) of organic solvents (DEAf plus hexane) measured by GC aft er hydrolysis of the original specimen solution was about 53 %

Poisoning symptoms, and toxic and fatal concentrations

By the Tokyo Sarin Subway Incident, the poisoning symptoms provoked by sarin were clarifi ed [8] In its mild poisoning, rhinorrhea, darkness of eyeshot and diffi culty in breathing were most common, followed by pain of the eye, dyspnea, cough, nausea, vomiting, headache and feeling of enervation In severe poisoning, the victims are killed by paralysis of the respiration muscles

Sarin is highly volatile and shows toxicity higher than that of tabun In the presence of sarin

at 2 mg · min/m3 in the air, the darkness of the eyeshot and thus visual disturbance appear; the fatal atmospheric concentration was reported to be about 100 mg · min/m3 [8]

31 P- NMR spectrum in the 1 H decoupling mode for the original sarin specimen solution obtained

at the Tokyo Subway Sarin Incident.

⊡ Figure 1.7

a) As prerequisites of being the poisonous chemicals, the following 3 items can be men-tioned

• Very high toxicity: it should have toxicity, which can kill a number of humans or ani-mals with a small amount of a poison

• Stability under certain conditions: upon the use of a poison, the poisonous eff ect should last for a required period; upon its storage, it should be highly stable

• Low perceptibility of a poison by humans: a compound, which gives a characteristic smell, a color or a taste, is easily detected by one or more of the fi ve senses of humans

⊡ Table 1.2

1 H-, 13 C-, 31 P- and 19 F-NMR data obtained from sarin [5]

Nucleus Chemical shift (ppm) Coupling constants (Hz)

1 H

3JHF = 5.7

3JHP = 7.3

13 C

1JCP = 150.3

2JCF = 27.5

2JCP = 6.4

3JHP = 7.3 1JPF = 1045.4

⊡ Table 1.3

Chemical shift values for sarin, its related compounds and trimethyl phosphate [6].

(ppm)*

Coupling constant (Hz)

isopropyl hydrogenmethylphosphonate 32.80

* 85% phosphoric acid external standard

and can be treated for protection Th e compound should not be easily perceived by any human sense

In addition, the following items can be also mentioned as their common properties

• A poison should invade various structures and exert its homicidal action, but does not destroy or ruin the structures themselves

• A poison can be spread widely, retained for a while to exert its poisonous eff ects and

fl own away

• Th ere are types of poisons with early (within several hours) and delayed onset of poi-soning symptoms

• Th ere are short (within 10 min) and long-acting poisons

• Because of the low perceptibility of a poison, people are easily exposed and injured by the poison without any consciousness

b) sarin/isopropyl hydrogenmethylphosphonate/methyl phosphonic acid

c) As reagent gas, ammonia or methane can be also used

d) Th is compound is an impurity produced by decomposition of methylphosphonic difl uo-ride, the precursor of sarin, or of methylphosphonic chlorofl uouo-ride, the disproportionation reaction product

e) Methylphosphonic dichloride side-reacts with isopropyl alcohol to produce diisopropyl methylphosphonic acid

f) DEA is considered to be added to enhance the reaction of the sarin synthesis

References

1) Wakai H (2000) Defense against chemical weapon attack Japanese Bureau of the Organization for the Prohibi-tion of Chemical Weapons (OPCW), Tokyo, pp 142–155 (in Japanese)

2) Komoto T (1995) Basic knowledge on chemical weapons Criminal Data File of the Metropolitan Police Depart-ment (Tokyo) 46:17–36 (in Japanese)

3) Ando H (1995) Practical study on sarin analysis at the Tokyo Subway Sarin Incident In: Abstracts of the 1995 Annual Meeting of Kanto District Society of Forensic Technology Tokyo, pp 49–56 (in Japanese)

4) Miyata Y, Nonaka H, Yoshida T et al (2000) Analyses of sarin and related compounds used in the Tokyo Subway Sarin Incident Jpn J Forensic Toxicol 18:39–48

5) Miyata Y, Nonaka H, Ando H (2000) Nuclear magnetic resonance data of sarin obtained at the Tokyo Subway Sarin Incident Jpn J Forensic Toxicol 18:261–267

6) Miyata Y, Ando H (2001) Examination of an internal standard substance for the quantitative analysis of sarin using 31 P-NMR J Health Sci 47:75–77

7) Japanese Association of Organic Synthetic Chemistry (ed) (1971) Organophosphorus compounds In: Modern Organic Synthesis Series (5) Gihodo, Tokyo, pp 329–330 (in Japanese)

8) Tu AT, Inoue N (2001) Overall View of Chemical and Biological Weapons Joho Inc., Tokyo, p 27, p 82 (in Japanese)