Toxic Organic Compounds in Air (EPA TO14 & TO15)

In this case, canister sampling has clear benefits over traditional forms of active sampling using Tedlar bags and sorbent tubes.  Samples can be collected using Silonite coated MiniCans and new low-cost Bottle-Vacs and this gives you the following advantages:
 

• Easy field sampling
• All chemistry is undertaken in the laboratory
• Very little training is required to collect valid samples
• Sampling is undertaken in the same manner independent of concentration, analytes to monitor or humidity and temperature
• Recoveries are more reliable
• Less matrix interactions
• Wide range of sample collection times (from seconds to days)
• Widest possible range of analytes
   

The sample can be taken either as a grab sample in a few seconds, or with the utilisation of critical orifice technology sampling can be time integrated for industrial time weighted averages (TWA).

Further benefits over conventional sorbent tube analysis include the absence of analytical breakthrough as a source of gross errors, and the ability to analyse the same sample multiple times without the need to re-sample.

This whole gas sampling approach is essentially non-selective which effectively removes the requirement to use multiple sorbent tubes (or sorbent types) to target specific compound volatility and/or chemical functionality.  This can mean that a single analytical method can be used to evaluate the whole sample.  In addition, the sampled atmosphere can be stored for extended periods of time (up to 30 days) without detrimental effect to the sample composition. 

This technology has been applied to a wide range of ambient air characterisation projects including TO14/TO15, ultra high sensitivity analysis of landfill gas samples from Tedlar bags, domestic air sampling, and through the use of the Entech Thermal Transfer System, the ability to transfer species adsorbed onto conventional sorbent tubes into Bottle-Vac Samplers for storage or analysis.

Unlike adsorbent-based sampling devices, whole air samplers are uniquely capable of completely mixing the collected sample with a surrogate or internal standard pre and post-sampling; another benefit to the canister based collection technique.