Abstract: An experimental comparison device for dissolved oxygen determination has been built in the laboratory to explore the difference between optical method and classical Winkler titration under different temperature and dissolved oxygen concentration conditions. The results show that the correlation between optical sensors and classical Winkler titration is good with correlation coefficient higher than 0.998 at different temperatures. Dissolved oxygen measured by optical sensors is slightly lower than that of classical Winkler titration in the concentration of dissolved oxygen lower than 4 mg·L^-1. The difference values between optical sensors and classical Winkler titration are mainly concentrated in -0.25~0.25 mg·L^-1 when the concentration of dissolved oxygen is higher than 4 mg·L^-1. The results measured by two kinds of optical sensors are close, and the difference is less than 0.10 mg·L^-1. This result proves that optical sensor is a reliable method for detecting dissolved oxygen, which can be applied to marine survey and conventional on-line monitoring in aquaculture areas.

Key words: dissolved oxygen, optical sensor, classical Winkler titration