This study has demonstrated a spectrophotometric method for residual hydrogen peroxide analysis in wood pulp bleaching streams. In an acidic medium, hydrogen peroxide can instantly associate with molybdate to form a peroxomolybdic acid complex that has an absorption peak at 330 nm. To avoid the spectral interference from excess molybdate ion, 350 nm is used for spectroscopic quantification. A linear relationship between the absorbance at 350 ran and peroxide concentration was found up to a peroxide concentration of ca. 0.2 mmol l(-1). It was discovered that 297 nm was an isosbestic point that could be used to develop a dual-wavelength method to account for the spectral interference from dissolved lignin in pulp bleaching streams, a critical procedure for the success of the present method. This method is simple, rapid, sensitive, accurate, and has the potential for on-line applications. (C) 2003 Elsevier B.V. All rights reserved.
