HONO Measurement by Differential Photolysis

Nitrous acid (HONO) has been quantitatively measured in-situ by differential photolysis at 385 and 395 nm and subsequent detection as nitric oxide (NO) by the chemiluminescence reaction with ozone (O3). The technique has been evaluated by FT-IR to provide a direct HONO measurement in a simulation chamber, and compared side-by-side with a LOng Absorption Path Optical Photometer (LOPAP) in the field. The NO/O3 chemiluminescence technique is robust, well characterized and capable of sampling at low pressure whilst solid-state converter technology allows for unattended in-situ HONO measurements in combination with fast time resolution and response.