Surfactant Enhanced Resonance Rayleigh Scattering Method for the Determination of Dissolved Oxygen in Environmental Water

Abstract

A novel method for the determination of trace amounts of dissolved oxygen based on resonance rayleigh scattering (RRS) has been developed. Dissolved oxygen in the water sample was fixed by adding MnSO₄ in an alkaline medium to form Mn(OH)₃ from which oxygen was liberated upon addition of H₂SO₄ and reacted with the I₃^– liberated by the reaction of KI with H₂SO₄. In the presence of polyvinyl alcohol (PVA), I₃^– reacted with malachite green (MG) to yield I₃^–-MG-PVA complex, which results in the enhancement of resonance rayleigh scattering intensity and the appearance of the corresponding resonance rayleigh scattering spectral characteristics. The maximum scatter peak was at 474 nm for the I₃^–-MG-PVA system. The enhanced resonance rayleigh scattering intensity was directly proportional to the concentration of I₃^–. On the basis of these reaction, KIO₃, as the standard solution of the dissolved oxygen, reacted with excessive KI and malachite green in the polyvinyl alcohol solution and formed the I₃^–-MG-PVA complex. Thus the content of dissolved oxygen could be measured from the standard curve prepared by using KIO₃ standard solution as standard for dissolved oxygen. The optimum conditions of these reactions and the influencing factors have been investigated. In analyzing different water samples, results obtained by the resonance rayleigh scattering method were in consistency with the results obtained by the Winkler method.