Ring test of a method for assessing the phototransformation of chemicals in water

Seven types of apparatus have been used to measure the quantum yields for direct phototransformation in water of 4 chemicals (pentachlorophenol; 2,4-dichlorophenol; 3,4-dichloroaniline; 4-nitrophenol) under polychromatic (12 laboratories) and monochromatic (3 laboratories) light, according to a common test protocol. The results with both types of light were in good agreement. The reproducibility and accuracy of quantum yields obtained with the ECETOC/University of Clermont-Ferrand apparatus with polychromatic light (6 laboratories) were similar to or better than those obtained with monochromatic light. A disadvantage of the method with polychromatic light is that the calculation is more complicated, but this can be overcome by the use of a desk-top computer. On the other hand experiments with polychromatic light permit the determination of quantum yields of substances of low photoreactivity.