A Diffusion Scrubber for the Collection of Gaseous Nitric Acid

Abstract

A diffusion denuder with a thin anion exchanger membrane tube as the collecting element and with a scrubber solution flowing in a narrow annular gap outside the membrane is described. The use of this device with a dilute sulfate-sulfamic acid solution as scrubber has been exploited for collecting nitric acid. The method is essentially free from interference due to NO₂, and response characteristics are described for a continuous flow application. Direct UV detection, used to demonstrate response characteristics in the continuous monitoring mode, is not sufficiently sensitive for the measurement of low levels of ambient gaseous HNO₃.