Optimized Operation and Calibration Procedures for Radical Amplifier-Type Detectors

Abstract

Laboratory experiments were conducted to improve the operation and calibration procedures for the ambient ROx radical detectors (ROx = HO2 + RO2 + OH + RO) based on chemical amplification. A new method for the experimental determination of the effective ratio between the absorption cross sections for water and molecular oxygen at 184.9 nm was developed and used to reduce the uncertainties associated with the peroxy radical source based on water photolysis. A novel peroxy radical source based on OCIO was developed and employed to confirm the ambient humidity effect on the chain length of the radical detector. The humidity effect on the chain length can be reduced by heating the walls of the reactor and decreasing the residence time of the air sample in the reactor to avoid the possible interferences from thermolabile species.