DETECTION OF 2-CHLOROETHYL ETHYL SULFIDE END SULFONIUM ION DEGRADATION PRODUCTS ON ENVIRONMENTAL SURFACES DOING STATIC SIMS

2-Chloroethyl ethyl sulfide (CEES) is a simultant for the chemical war fare agent bis(2-chloroethyl)sulfide (also known as HD or mustard), an d both molecules undergo hydrolysis and subsequent condensation in aqu eous solution to form stable sulfonium ions. The sulfonium ions derive d from CEES are directly detected on quartzic surfaces using static SI MS instrumentation, which employs a molecular ReO4- (250 D) primary io n and pulsed secondary ion extraction. Pulsed extraction mitigates sur face charging, and the ReO4- primary particle is efficient at sputteri ng molecular surface species into the gas phase. CEES eliminates Cl- t o form an ethyl thiiranium intermediate, which is susceptible to nucle ophilic attack by water and methanol to form 2-hydroxyethyl ethyl sulf ide and 2-methoxyethyl ethyl sulfide. These two products and unhydroly zed CEES also function as nucleophiles that condense with the ethyl th iiranium intermediate, resulting in the formation of sulfonium ion agg regates that are observable using SIMS. The previously unreported meth oxy-substituted sulfonium ion suggests that a variety of derivatives a re possible if different nucleophiles are present in the vicinity of t he ethyl thiiranium intermediate. This work demonstrates that the sulf onium ion aggregates are stable on mineral surfaces and also demonstra tes the potential value of SIMS for the detection of unanticipated ion ic species in monitoring applications where mustard and its degradatio n products are suspected.