SO2 sorption characteristics of air sampling filter media using a new laboratory test

A significant factor in the selection of filter media used for air sampling is the formation of artifacts due to the sorption of sulfur and nitrogen oxides on the filter. These artifacts can erroneously increase measured particulate concentrations. A technique is developed to measure the uptake of SO2 and other gases and vapors on air sampling filter media. The static chamber technique features in-chamber measurements of SO2 concentrations using FTIR spectrometry. The filter uptake, partition coefficient, and diffusion coefficient are estimated from the loss of gaseous SO2 in the chamber. The technique provides rapid and precise results over a wide range of filter characteristics and avoids problems related to the extraction of target analytes from the filter. A total of 12 types of filters are evaluated, including glass fiber, Teflon-coated glass fiber, nylon, quartz fiber, Teflon, Supor, Nylasorb, and acrylic copolymer membranes. Results indicate that Teflon, quartz and acrylic copolymer filters have minimal sorption of SO2 while quartz fiber, Supor and Nylasorb filters have high to moderate uptake of SO2.