Particle collection efficiency of sorbent tubes
Both the airborne particulates and the gas-phase VOC and SVOC are of importance for indoor air quality. The sampling of the various species, however, utilizes different techniques - it is a common procedure to sample particles on filter disks. whereas the gaseous compounds are trapped on solid sorbents. In many cases, the distribution coefficient of semivolatile organic compounds between the particulate and the gas phase are calculated by measuring gas phase and particulate phase concentrations of a certain substance. In some cases, such measurements were carried out in parallel. In this study, the collection efficiency of standard solid sorbent tubes for thermal desorption filled with Tenax TA was determined. The tubes were challenged with a polydisperse NaCl particles with count median diameter 120 nm and particle concentration and size distribution upstream and downstream of different sorbent tubes was measured by SMPS. The overall collection efficiency for particles in the size range of 20-700 nm was found to be close to 90 % for most tubes, thus indicating that particles as well as gaseous substances will be collected in these tubes and that sampling for the calculation of partitioning coefficients should only be carried out with specially designed combination samplers.