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HSE report on  uptake rates for Markes axial samplers
Categories: Passive sampling Thermal desorption Thermal desorption tube sampling

HSE Report – Diffusive sampler uptake rates

Tests for a range of compounds onto four sorbent types over periods of 1 and 2 weeks

Markes International commissioned the Science Division (SD) of the Health and Safety Executive (HSE) to undertake testing of thermal desorption type passive tube samplers containing four different sorbents. This work is described in project proposal HSE-SD Uptake Rate Tests PE08609. The objective of this study was to enable the determination of diffusive uptake rates for a range of analytes on these samplers by exposing them to low levels of chemical vapours under controlled conditions.

Before commencing the uptake rate tests, HSE generated a vapour comprising a mixture of 21 volatile organic compounds (VOCs) in air using bespoke standard atmosphere generation equipment and undertook a 10-litre breakthrough test on the two sorbents to be used for active sampling. This showed that the proposed test conditions were suitable for all of the components, with the exception of dichloromethane. After consultation with Markes, it was therefore agreed to remove this compound from the test mix and replace it with n-hexane.   

HSE then proceeded to expose sets of samplers to an atmosphere of the 21 compounds each at a nominal target concentration of 5 parts per billion (ppb). For these tests exposure times of 1 and 2 weeks were used. In addition, HSE collected samplers using pumped sampling for approximately 24-hour periods and accurately recorded collected sample volumes. At the end of the test the diffusive and pumped samplers were collected, sealed and returned to Markes for analysis. On supply of GC–MS data HSE calculated concentrations of the target compounds in the chamber over the exposure period and uptake rates for these compounds over the 1- and 2-week periods.  

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