Spectrophotometric Determination of Dissolved Oxygen in Water Sample with the System of I3–-Malachite Green-Polyvinyl Alcohol

Abstract

A new spectrophotometric method with the system of I₃^–-malachite green (MG)-poly(vinyl alcohol) (PVA) was first proposed for determination of dissolved oxygen in water sample. The I₃^– which reacted with malachite green to form an ion-associated complex has a characteristic abosrbance at 699 nm. KIO₃ which adopted as the primary standard substance was used to determine the dissolved oxygen directly. The calibration graph was linear over the range of 0.05-1.70 μg/mL IO₃^– (0.0137-0.466 mg O₂/L). The relative standard deviation (n = 6) was below 0.3 %. A complete analysis could be performed in 0.5 h including pretreatment and detection, giving a high throughput of 20 samples in about 40 min. Compared with the Wrinkler methods, this method is simple and sensitive and consumes limited and cheap reagents. It was successfully applied for the determination of dissolved oxygen in fresh or seawater samples, sewage, etc. It is suggested as a suitable alternative to titration in most applications of the Winkler determination of dissolved oxygen.