Water quality — Determination of dissolved oxygen — Electrochemical probe method

Electrochemical measurement of dissolved oxygen for drinking waters, natural waters, waste waters, and saline waters is a very important tool to assess the water quality. It is necessary to measure dissolved oxygen, because it is one of the most important index of the survival of aquatic organisms. The higher dissolved oxygen reflects the higher health degree of water ecosystem.

Standard Reference

ISO 5814:2012 Water quality — Determination of dissolved oxygen — Electrochemical probe method

The Principle

ISO 5814:2012 specifies an electrochemical method for the determination of dissolved oxygen in water by means of an electrochemical cell which is isolated from the sample by a gas permeable membrane.

Measurement can be made either as a concentration of oxygen in milligrams per litre, percentage saturation (% dissolved oxygen) or both. The method measures oxygen in water corresponding to 1% to 100% saturation. However, most instruments permit measurement of values higher than 100%, i.e. supersaturation.

The method measures oxygen in water with a saturation higher than 100 %, when special arrangements to prevent the outgassing of oxygen during the handling and measurement of the sample are made.

The DO Meters

The DO meters is suitable for measurements made in the field and laboratory.

The portable meter is suitable for fields measurements and out door measurements.

The portable meter has the Silicone rubber case and Wristbands.

The Factors of dissolved oxygen

The factors of dissolved oxygen in water include abiotic factors such as altitude, air pressure, temperature, salinity, wind and hydrodynamic conditions, as well as biological communities such as higher aquatic plants and phytoplankton.

• Temperature compensation

The DO meters has the automatic/manual temperature compensation to ensure accurate results.

• Pressure compensation

The 400F, 500T, 510T, 310F series meters have auto barometric pressure compensation function.

The DO210E has manual barometric pressure compensation function.

• Manual Salinity compensation

The DO meters have manual salinity factor correction.

If used for saline waters, such as sea or estuarine waters, a correction for salinity is essential.