On-line Measurement of Sub-ppb Level Hydrogen Peroxide in Ultrapure Water Production Process

An on-line H₂O₂ analyzer was developed for application to the ultrapure water production process, using a gasometric method. The analyzer consists of a dissolved oxygen (DO) sensor and analyzer, a catalyst that converts H₂O₂ to O₂, and a computer that stores the DO data. H₂O₂ concentrations were calculated by measuring the change in DO concentration before and after the catalyst and using the calculation formula presented in this study. In order to accurately analyze a sub-ppb level of H₂O₂, a DO meter which can correctly measure the DO concentration at the ppb level was applied. An ion exchange resin with Pd, was selected as an appropriate catalyst since it could decompose 99% of H₂O₂ to O₂ at a space velocity of 120/h. The minimum analysis time was 20 min, and the detection limit was observed to be 0.27 ppb. When the DO concentration of the sample was 1.5 ppb or lower, an H₂O₂ concentration of 1 ppb or lower was successfully measured. Good correlation, with an R² value of 0.99, was observed between the measured and calculated H₂O₂ concentrations.