The catalytic oxidation of 14CO in a flow reactor used to measure atmospheric hydroxyl radical concentrations

Abstract

Measurements of ultra-low CO oxidation rates of materials suitable for construction of a hydroxyl radical monitor are described. The procedure consists of passing an ultrapure ¹⁴CO tracer over the test material and collecting the resultant ¹⁴CO₂. Oxidation rates are measured for stainless steel, aluminum, alumina, titanium, and Teflon. Results show the oxidation rate with aluminum is at least an order of magnitude less than any other material (<10⁴ cm⁻²s⁻¹). These rates are three to four orders of magnitude lower than reported previously in the literature. Application to a ground-based hydroxyl monitor is discussed.