Development of a Photometric Method to Measure Molecular Oxygen in Water

• Published in: Analytical Sciences Vol. 37; no. 6; pp. 839 - 844
• Main Authors: DANG, Tu, KAWAGISHI, Hiroto, FUJII, Yusuke, OKITSU, Kenji, MAEDA, Yasuaki, TAKENAKA, Norimichi
• Format: Journal Article
• Language: English
• Published: Singapore The Japan Society for Analytical Chemistry 10.06.2021; Springer Nature Singapore; Japan Science and Technology Agency
• Subjects: Analytical Chemistry; Chemistry; coacervate reaction; Dissolved oxygen; High temperature; Manganese; Metal ions; Optical measuring instruments; Original Paper; Oxygen; Photometry; ultrafine bubbles oxygen; UV/vis photometry; Water analysis; Water sampling; Winkler method; ultrafine bubbles oxygen; Dissolved oxygen; coacervate reaction; UV/vis photometry
• ISSN: 0910-6340; 1348-2246
• DOI: 10.2116/analsci.20P316

A photometric method to determine molecular oxygen in water was developed. When manganese(II) is oxidized by oxygen under alkaline conditions, the presence of polyphosphate can prevent precipitation due to a coacervate reaction. The oxidized manganese later dissolves in acid to form a pink Mn(III) species, which has a stable UV/vis spectrum. Monitoring of the oxygen concentration based on the absorbance of the pink Mn(III) species at 517 nm showed a strong correlation with both the Winkler method and an optical sensor. As a result, the present method can measure not only dissolved oxygen, but also fine bubbles oxygen in in the water sample with high reliability (0 – 26 mg dm−3, r2 = 0.9995). During this process, no significant interference from nitrite or metal ions was observed. The accuracy of the measurement was steady at high temperatures of the water samples (≤ 363 K).