Overview

This International Standard specifies an optical method for the determination of dissolved oxygen in water using a sensor working on the basis of fluorescence quenching. The measurement result can be indicated either as a concentration of dissolved oxygen in milligrams per litre and/or as relative percentage saturation (%). Depending on the instrument used, detection limits of 0,1 mg/l or 0,2 mg/l can be reached according to the manufacturer's manual. Most instruments permit measurement of relative saturation greater than 100 %, for example oversaturation. Oversaturation is possible when the partial pressure of oxygen is greater than in air. Oversaturation up to 200 % and more is possible, especially in the case of strong algae growth. With saturation greater than 100 % determination of oxygen in water is then possible if special precautions are taken in order to prevent the outgassing of oxygen during the handling and measurement of the sample. Similarly, it is important that the transport of oxygen into the sample is prevented if the saturation is below 100 %. The method is suitable for measurements made in the field and for continuous monitoring of dissolved oxygen as well as measurements made in the laboratory. It is one of the preferred methods for highly coloured and turbid waters as well as for waters that contain iron- and iodine-fixing substances and thus due to the interferences in the iodometric method specified in ISO 5813 are not suitable for the Winkler titration method. The method is suitable for drinking waters, natural waters, waste waters, and saline waters. If used for saline waters such as sea or estuarine waters, a correction of the oxygen concentration values as a function of salinity is essential. This document has been prepared by Technical Committee ISO/TC 147 "Water quality", the secretariat of which is held by DIN (Germany). The responsible German committee is NA 119-01-03-01-21 AK "Gelöstsauerstoffmessung" ("Measurement of dissolved oxygen") of Working Committee NA 119-01-03 AA "Wasseruntersuchung" ("Water examination") of the Water Practice Standards Committee (NAW).

Document: references other documents

Document: referenced in other documents

Responsible national committee

NA 119-01-03-01-21 AK - Measurement of dissolved oxygen (ISO/TC 147/SC 2/WG 62)  

Responsible international committee

ISO/TC 147/SC 2 - Physical, chemical and biochemical methods