Confirmatory lab tests have verified that the contents of a roadside bomb that exploded in Baghdad last month was the nerve agent sarin. Also known as GB, sarin is a potent cholinesterase inhibitor and bears the chemical name O-isopropyl methylphosphonofluoridate.
Initial field tests using an improved version of the Army’s Chemical Agent Monitor (CAM) and M8 detector paper indicated the presence of sarin in the 155-mm artillery shell that was rigged as a bomb. M8 alerts military personnel to the presence of a chemical agent. The more sophisticated portable CAM distinguishes among nerve and mustard agents but is notorious for yielding false positives.
A U.S. official who asked not to be identified tells C&EN that follow-up lab analyses performed by the Iraq Survey Group confirmed the presence of “sarin and a major degradation product, diisopropyl methylphosphonate.”
Liquid samples from the partially exploded shell were analyzed using gas chromatography/mass spectrometry and Fourier transform infrared spectroscopy, this official says. The lab report does not discuss sarin’s purity or concentration, the official says.
Days after the explosion, U.S. military spokesman Brig. Gen. Mark Kimmitt described the artillery shell as predating the 1991 Persian Gulf War and binary in design. Iraq admitted to having an R&D program to create a sarin binary shell but claimed not to have deployed such a munition. In a binary system, sarin is formed when methylphosphonyl difluoride, or DF, and isopropanol mix after the artillery shell is fired.
Jonathan B. Tucker, a senior researcher in the Washington, D.C., office of the Monterey Institute of International Studies, says if the shell was of binary design, the precursor chemicals didn’t mix well. Its detonation caused only minor symptoms of sarin exposure in two soldiers.