THE DETERMINATION OF HYDROXYL RADICAL CONCENTRATIONS IN ENVIRONMENTALCHAMBERS USING ELECTRON-SPIN-RESONANCE

A simple sampling and analytical method for the determination of OH ra dical concentrations in air is described, as applied to the characteri zation of air in closed environmental chambers. High-volume sampling t hrough a filter paper impregnated with alpha-(4-pyridyl 1-oxide)-N-ter t-butylnitrone leads to the formation of an OH-spin adduct. After extr action into toluene the adduct is analysed by electron spin resonance spectroscopy. Unambiquous identification and quantification of OH radi cal concentrations is achieved, giving a detection limit of approximat ely 5 x 10(4) radicals cm-3 of air and a precision of +/- 25%.