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Air monitoring - The respective advantages and applications os canisters and tube
Chris Llewellyn (1), Nicola Watson (1) and Danilo Pierone (2)
(1)Markes International Ltd, Gwaun Elai Medi Science Campus, Llantrisant, RCT, CF72 8XL, UK. (2)Nova Analítica, São Paulo, SP, BR

 

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Volatile (vapor-phase) organic air toxics or ‘Hazardous Air Pollutants’ (HAPS) are monitored in many industrial and urban environments as a measure of air quality. They range in volatility from methylchloride to hexachlorobutadiene & trichlorobenzenes and include some polar as well as apolar compounds. Several national and international standard methods have been developed for air toxics and related air monitoring applications. Key examples include: US EPA Method TO-17 and TO-15, ASTM D-6196-03 and D-5466, ISO EN 16017 and ISO EN 16000-6. All these standards specify air sampling using either canisters or sorbent tubes with subsequent analysis by thermal desorption (TD)–GC-MS.
In response to increasing demand for ambient air toxics monitoring around the world, cryogen-free TD technologies have now been developed which offer an automated, method-compliant analytical platform for both canisters and tubes. The latest systems typically feature innovations such as repeat analysis for sorbent tubes together with internal standard addition options for both canister and tube operation.
As evidenced by US EPA Methods TO-15 and TO-17, both canisters and sorbent tubes are compatible with air toxics in typical ambient concentrations i.e. at 0.1 to 25 ppb levels. However, for compounds outside the methylchloride to hexachlorobutadiene range and for other air monitoring applications there are differences between the two sampling methods which can make one technology more suitable than the other for a particular situation. In effect, canisters and sorbent tubes provide complementary sampling technology allowing analysts equipped with both to address a larger range of air monitoring applications than either method on its own.

This work presents in detail the technical features of tubes and canisters and respective air monitoring applications. A summary of canisters and sorbent tubes advantages for different air monitoring applications is presented. The two sampling techniques are evaluated for: volatility of the investigated compounds, practical/operating differences between the two techniques, cleaning procedures and cleaning costs/time considerations.