Minimizing Errors in Measured Yields of Particle-Phase Products Formed in Environmental Chamber Reactions: Revisiting the Yields of β-Hydroxynitrates Formed from 1-Alkene + OH/NOx Reactions

Environmental chamber studies are widely used for measuring the yields of reaction products and secondary organic aerosol formed from the oxidation of volatile organic compounds, information that can be subsequently used to develop chemical reaction mechanisms and models of atmospheric chemistry. Such measurements are challenging, however, and many potential sources of errors are not always appreciated. Here, we describe methods for minimizing and accounting for uncertainties associated with the chamber volume, gas and particle sampling, instrument calibrations, gas-wall partitioning, particle deposition to walls, and secondary reactions with OH radicals and demonstrate these methods by measuring yields and branching ratios for the formation of beta-hydroxynitrates from reactions of C-14 and C-15 1-alkenes with OH radicals in the presence of NOx Experiments were conducted in a Teflon environmental chamber and included Tenax sampling of alkenes with analysis by gas chromatography with flame ionization detection, filter sampling of particle-phase beta-hydroxynitrates and dioctyl phthalate seed particles with analysis by liquid chromatography with UV/vis detection, and measurements of aerosol volume concentration and composition using a scanning mobility particle sizer and thermal desorption particle beam mass spectrometer. The measured yields of beta-hydroxynitrates are similar to 25% higher than those determined previously using similar methods whose uncertainties were less well minimized and characterized.

Automated summary

Environmental chamber studies are essential for measuring reaction product yields and secondary organic aerosols formed from the oxidation of volatile organic compounds to develop atmospheric chemistry models. These measurements are challenging due to various potential sources of errors that need careful consideration and mitigation.