TABLE 2-1 Physical and Chemical Properties of Sarin and Cyclosarin

Characteristic

Sarin

Cyclosarin

Chemical name

Isopropyl methylphosphonofluoridate

O-Cyclohexyl-methylfluorophosphonate

Synonyms

Methylphosphonofluoridate, isopropyl ester

Cyclohexyl methylphosphonofluoridate (CMPF)

Chemical formula

C4H10FO2P

C7H14FO2P

Chemical structure

Molecular weight

140.10

180.2

CAS Registry Number

107-44-8

329-99-7

Physical state

Colorless liquid

Liquid

Solubility in water, g/L

Miscible with water

0.37% (20°C); almost entirely insoluble in water

Vapor pressure

2.10 mm Hg at 20°C

0.044 mm Hg at 25°C

Data from DA, 1990. Table modified from NRC, 2003.

of 100–500 mg through the skin, or 50–100 mg-min/m3 by inhalation (in a person who weighs about 70 kg) (Somani, 1992).

In the blood, sarin interacts with several esterases. Some, such as paraoxonase, hydrolyze sarin to inactive metabolites (Davies et al., 1996; Lotti, 2000). Two others—acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)—irreversibly bind to sarin. Those esterases in the blood are often described as false targets—by binding irreversibly to sarin, AChE and BuChE sequester sarin in the blood, thereby preventing some or all of it from reaching the central nervous system (CNS), depending on the dose (Spencer et al., 2000).

Distribution and Elimination

Animal data obtained by using radioactively labeled sarin indicate that sarin rapidly (within 1 min) distributes to the brain, lungs, heart, diaphragm, kidneys, liver, and plasma; the greatest concentrations are found in the last three (Little et al., 1986). The concentrations in all tissues decline rapidly; a decrease of 85% within 15 min was followed by a second, more gradual decline. The initial, rapid decline appears to be mediated by metabolism, not urinary elimination of the parent compound, inasmuch as about half the labeled sarin was associated within



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