Dissolved oxygen analyses are performed with an SIO/ODF-designed automated oxygen titrator using photometric end-point detection based on the absorption of 365nm wavelength ultra-violet light. The titration and data logging are controlled by ODF PC software compiled in LabView.
The ODF method uses a whole-bottle modified-Winkler titration following the technique of Carpenter [Carpenter, J. H., “The Chesapeake Bay Institute technique for the Winkler dissolved oxygen method,” Limnology and Oceanography, 10, pp. 141-143 (1965)] with modifications by Culberson et al. “A comparison of methods for the determination of dissolved oxygen in seawater,” Report WHPO 91-2, WOCE Hydrographic Programme Office Aug 1991. A summary can also be found here.
Concentrations of potassium iodate standard is approx 0.012N and thiosulfate solution is approx 55 gm/L. Thiosulfate is dispensed by a Dosimat 665 buret driver fitted with a 1.0 mL buret. Standard KIO3 solutions are prepared in-house and run daily. Reagent/distilled water blanks are also determined to account for presence of oxidizing or reducing agents.