Counter-terrorism – monitoring key civilian locations
The recent global rise in terrorism has enhanced the need to monitor key civilian locations, such as government facilities, for compounds that present an immediate and severe threat to human health (e.g. the G- and V-type nerve agents). These range from the Schedule 1 compounds through to Schedule 3 compounds (as defined by the Chemical Weapons Convention), with certain toxic industrial chemicals (TICs) also of concern because of their availability.
This need is addressed by near-real-time (NRT) monitoring, whereby air streams are continuously sampled for the presence of hazardous compounds, providing an early alert in the event of a chemical incident. Organisations such as the US Centers for Disease Control and Prevention (CDC) have defined parameters for NRT monitoring, including no ‘blind spots’ and completion of the entire sampling and analytical process within 15 minutes.
Airborne nerve agents are toxic at extremely low concentrations, and exposure limits are correspondingly low – for example, the current US airborne exposure limit for VX is just 0.001 µg/m3 (ca. 0.1 ppt). Conventional GC systems cannot detect these concentrations with certainty, making pre-concentration of the air or vapour sample by thermal desorption essential.
|Detecting free-VX || |
One of the most difficult nerve agents to monitor is the nerve agent VX, which as well as being highly reactive, has a high boiling point (298°C) and a correspondingly low vapour pressure. These problems have led many analysts to use methods that derivatise VX to the more stable ‘G’ analogue before analysis.
Unfortunately, derivatisation is often incomplete or inefficient, producing unreliable results. Markes has addressed this by ensuring that our instruments allow the detection of trace-level ‘free’ (underivatised) VX, as well as many other challenging analytes.
What Markes can offer
Markes’ TT24-7 thermal desorber meets the challenges posed by nerve agent detection in a homeland security context, by providing continuous monitoring without ‘blind spots’ and (when used with fast GC), response times of 15 minutes or less.
Additionally, use of time-of-flight (TOF) mass spectrometers such as BenchTOF can provide the information-rich datasets that enable the rapid screening for both known and ‘unknown’ trace-level toxins using software like Markes’ TargetView compound-identification package.
- For more background to chemical warfare agents and the analytical challenge they pose, see: T. Murphy, G. Roberts and G. Davies, Chemical warfare agents and use of thermal desorption-GC-MS to achieve improved trace-level detection, Spectroscopy, April 2009.
- For an example of the detection of CWA simulants with an analytical setup using the TT24-7, fast GC and BenchTOF, see: J. Leppert, G. Horner, F. Rietz, J. Ringer, P. Schulze Lammers and P. Boeker, Near real time detection of hazardous airborne substances, Talanta, 2012, 101: 440–446.
- For examples of the use of thermal desorption to analyse trace-level high-boiling compounds with similar characteristics to many CWAs, see Application Notes 034 and 039.
- For more detail on the detection of free-VX using thermal desorption, see Application Note 044.
- For information on the detection of trace-level chemical agents in air, see Application Note 063.