Determination of wavelength-averaged,near UV quantum yields for environmental chemicals

The present study describes a procedure for determination of an average quantum yield for the wavelength range of 310 to 410 nm. Solutions of the pollutant in sealed Pyrex tubes are irradiated in a Rayonet photoreactor fitted with fluorescent lamps emitting maximally at 355 nm. The integrated spectral overlap and the photolysis half-life for both the chemical actinometer and the pollutant are determined and from these data the quantum yield is calculated. The method has been evaluated by measuring quantum yields for organophosphorus, chlorinated hydrocarbon, and dinitroaniline pesticides and $\text{p}$-nitroanisole/pyridine mixtures. Corrected quantum yields are obtained on simultaneous irradiation of the trifluralin actinometer.