Excimer Laser Photofragmentation/Fragment Detection for Analysis of the Oxygenated Hydrocarbon Ethyl-3-Ethyoxypropionate: Implications for Atmospheric Monitoring

Abstract

In the present study, the use of ArF excimer laser photofragmentation/fragment detection (PF/FD) is considered for the characterization of gaseous ethyl-3-ethyoxypropionate (EEP), a representative solvent within the class of oxygenated volatile organic compounds (VOCs). PF/FD measurements of EEP resulted in identification of the resulting photofragments as C₂ and CH, allowing photofragmentation pathways to be proposed for the parent molecule for the first time. In addition, PF/PD measurements of EEP recorded in the presence of sodium-based aerosol particles resulted in a reduced signal from the EEP, indicating adsorption onto the particulates, thereby demonstrating proof-of-concept that PF/FD can be used to study heterogeneous chemical reactions relevant to atmospheric chemistry. Finally, both time-integrated and time-resolved measurements of the EEP photofragmentation signal in varying concentrations of oxygen revealed that oxygen effectively acts as a dynamic quencher of the EEP signal. In consideration of oxygen quenching, care must be taken in calibrating/analyzing data in selected applications of PF/FD for VOC characterization (such as combustion emission monitoring) in order to account for the potential variability of oxygen concentration.