Analysis of a spring water

Calibrating the electrode can be done in several ways:

• By finding two points on the calibration straight line: 1. The zero point (no dioxygen at all) is obtained using a saturated solution of sodium thiosulfate (Na₂S₂O₃) or dithionite (Na₂S₂O₄), saturated solution, prepared less than one month in advance. 2. Another point is found with a calibrated solution. This solution has been saturated with a known concentration of dioxygen (istilled water at 25°C, for example).
• By taking several measurements of dioxygen saturated solutions, at several partial pressures, to generate several calibration points.

The calibration curve is plotted against the dioxygen saturation rate (in %): ratio between the measured concentration under the given conditions, and the concentration of water saturated with dioxygen under identical conditions.