Sodium, fluid

Equipment : Roche Cobas Pro ISE

Method : Test principle An Ion‑Selective Electrode (ISE) makes use of the unique properties of ion‑selective membrane to develop an electrical potential (electromotive force, EMF) for the measurements of ions in solution. Selective membrane is in contact with both the test solution and an internal filling solution. Due to the selectivity of the membrane, only the ions to be measured contribute to the EMF. The membrane EMF is determined by the difference in concentration of the test ion in the test solution and the internal filling solution. The EMF develops according to the Nernst equation for a specific ion in solution The complete measurement system for a particular ion includes the ISE, a reference electrode and electronic circuits to measure and process the EMF to give the test ion concentration. The sodium2,3 and potassium4 electrodes are based on neutral carriers and the chloride5 electrode is based on an ion exchanger