A Multiple Parallel Plate Wetted Screen Diffusion Denuder for High-Flow Air Sampling Applications

Diffusion denuders are commonly used today for air sampling applications where it is necessary to discriminate between gaseous- and aerosol-phase analytes. In some applications, such as isotopic analysis, it is necessary to collect a sufficient analyte mass necessitating high sampling rates. Wetted denuders are preferred in many applications because they can be readily coupled to automated continuous analysis systems. We describe here a compact (5 cm diameter, 30 cm length) diffusion denuder with 11 individually wetted parallel screens (with an wetted area in excess of 0.1 m 2 ) that allow operation at high flow rates. The effluent liquid is collected at the bottom from two V-shaped grooves. With SO 2 as the test gas, ∼95% is collected even at a flow rate of 50 L/min with very low particle losses.