A Compact, High-Purity Source of Hono Validated by Fourier Transform Infrared and Thermal-Dissociation Cavity Ring-Down Spectroscopy

Abstract

A well-characterized source of nitrous acid vapour (HONO) is essential for accurate ambient air measurements by instruments requiring external calibration. In this work, a compact HONO source is described in which gas streams containing dilute concentrations of HONO are generated by flowing hydrochloric acid (HCl) vapour emanating from a permeation tube over continuously agitated dry sodium nitrite (span classCombining double low line"inline-formulaNaNO2) heated to 50&thinspspan classCombining double low line"inline-formulaspanC. Mixing ratios of HONO and potential by-products including NO,