Development and Laboratory Testing of an Automated Monitor for the Measurement of Atmospheric Particle-Bound Reactive Oxygen Species (ROS)

Abstract

Previous studies have found significant quantities of oxidative species associated with airborne particulate matter. Although oxidative stress is thought to be an important part of the mechanism by which particles produce adverse health effects, the lack of a suitable method to measure ROS on a routine basis has resulted in no work being undertaken to assess the effects of particle-bound ROS on health. In order to fill this need, an automated monitor for the continuous sampling of ambient aerosol and the measurement of concentrations of ROS on the sampled aerosol was developed. Potential methods to quantify ROS were compared in order to arrive at a suitable method to automate. The dichlorofluorescein (DCFH) fluorescence method was found to be the most non-specific, general indicator of particle-bound oxidants. Hence it was deemed the best suited method for the automated monitor. An integrated sampling-analysis system was designed and constructed based on collection of atmospheric particles in an aqueous slurry, and subsequent detection of the ROS concentration of the slurry using the DCFH fluorescence method. The results of the lab-scale investigation of the ROS sampling-analysis system suggested that the prototype continuous system was capable of detecting particle-bound ROS, and accounting for short-term variabilities in the same. The instrument was found to be capable of detecting nanomolar equivalent concentrations of ROS.

Acknowledgments

This work was supported by U.S. Environmental Protection Agency's Science to Achieve Results (STAR) Program through a subcontract from the University of Rochester PM and Health Center Grant RD832415 and by the Syracuse Center of Excellence CARTI project award, which is supported by a grant from the U.S. Environmental Protection Agency [Award No: X832325010]. Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency, it has not been subjected to the Agency's required peer and policy review and therefore, does not necessarily reflect the views of the Agency and no official endorsement should be inferred.

Notes

^a 2,2′-azobis (2-aminopropane) dihydrochloride, sonicated and incubated with DCFH.