THE APPLICATION OF THERMAL DESORPTION FOR THE ANALYSIS OF TRACE TOXIC COMPOUNDS IN AREAS OF HUMAN OCCUPATION

摘要

Accidental or deliberate release of toxic chemicals into the indoor or outdoor environment is a real threat in today's world (EmergencyNet NEWS 1995). The analysis of trace-level, vapourphase compounds in air requires thermal desorption (TD) to pre-concentrate the compounds before analysis by gas chromatography (GC), mass spectrometry (MS) or GCMS (Markes International.TDTSl2). This paper describes the latest continuous on-line monitoring technology with sub-ppt detection limits and pumped tube sampling with off-line analysis for monitoring human exposure at even lower levels. Rapid and accurate continuous monitoring is required in the most sensitive civilian locations in order to minimise loss of life in the event of a terrorist attack. A novel, peltier-cooled, twintrap sampling system is described which operates continually, with no blind spots, and enables near real time (NRT) analysis (cycle times ＜ 15 minutes) with sub-ppt detection limits. Performance examples are presented, including the analysis of free underivatised VX nerve agent, at low pg levels (Markes International Ltd.TDTS44).