radiello® Diffusive Air Sampling Application - OzoneThe adsorbing cartridge is formed by a micropore polyethylene tube filled with silica gel coated with 4,4’-dipyridylethylene and closed, at one end, by a PTFE cap. Upon exposure, acid-catalysed ozonolysis of 4,4’-dipyridylethylene leads to 4-pyridylaldehyde.