Tsunoda N., Seto Y., Kataoka M., Ohta H.

National Research Institute of Police Science, Department of Third Forensic Science , 6, Sabancho,Chiyoda-ku, Tokyo 102, Japan

Tear gas sprays have been marketed legally for personal protection in Japan. Recently, crimes of convenience store robbery and rape armed with tear gas spray gun have increased. In addition, people were attacked by strange fumes at public places, stations, trains or schools. In some cases, capsaicin-type tear gas sprays were detected as the caustic fumes. Generally, capsaicin have been determined by gas chromatography (GC) as its methyl- or trimethylsilyl derivative. In this study, a simple and rapid GC-mass spectrometry (MS) is described for the simultaneous identification of capsaicin, chloroacetophenone (CN) and o-chlorobenzalmalononitrile (CS) in forensic samples.
After liquid-liquid extraction, lachrymator ingredients were determined directly by GC-ion trap MS using a DB-5 or DB-1 capillary column with programmed oven temperature control. The full scanning GC-MS was performed in electron impact (EI) or isobutane chemical ionization (CI) mode. Straight-chain hydrocarbons were used for the calculation of retention indices (RIs).
Oleoresin Capsicum type tear gas sprays generally contain capsaicin and dihydrocapsaicin which constitute 80-95% of the total capsaicinoids. Capsaicin and dihydrocapsaicin can be identified directly with their RIs and diagnostic fragment ion peaks, m/z 137 as their base peak and m/z 305 and 307 as their molecular ions in EI mode. The established high resolution GC combined with EI- and CI-MS made it possible to identify not only capsaicin and dihydrocapsaicin, but also other irritants, CN, CS and nerve gas sarin and its related compounds.