1.1 This terminology covers those terms recommended by the International Union of Pure and Applied Chemistry (IUPAC),2 and is intended to provide guidance in the use of ion-selective electrodes for analytical measurement of species in water, wastewater, and brines. 1.2 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.