A Green Method to Determine VUV (185 nm) Fluence Rate Based on Hydrogen Peroxide Production in Aqueous Solution.

A mini-fluidic vacuum ultraviolet/ultraviolet (VUV/UV) photoreaction system (MVPS) was developed in our previous study. Based on the MVPS, a green method to determine VUV fluence rate has been developed using the production rate of H2 O2 when water is exposed to 185 nm VUV. The H2 O2 production followed pseudo-zero-order reaction kinetics well over the first 10 min of VUV/UV exposure. This new method was well calibrated with a standard cis-cyclooctene cis-trans photoisomerization actinometer as recommended by the International Union of Pure and Applied Chemistry. The apparent quantum yield for H2 O2 production by 185 nm VUV irradiation of water was determined to be 0.024 ± 0.002. As the solution pH increased from 5.0 to 8.0, the H2 O2 production rate decreased from 0.83 to 0.40 μm min-1 . Dissolved oxygen had a negligible influence on the H2 O2 production. This study proposes a novel VUV fluence rate determination method with advantages of nontoxicity, low detection limits, low costs and convenience, and it can be used as a good alternative to traditional actinometers.