Selective Ion Measurement
Measuring Ion Concentration
Each Ion Selective Electrode (ISE) is designed to detect a particular ion, within the concentration limits of the electrode.
The selectivity of the ion electrode is controlled by the type of internal sensing element and the type of membrane that seperates the internal element from the sample solution.
Electrode Types
There are four main classes of ISE, catagorized by their construction:
1. Solid state electrodes
2. Plastic electrodes
3. Gas sensing electrodes
4. Glass electrodes
LMS water supplies ion selective electrodes from several electrode manufacturers:
604IS (Ammonia) Electrode
This gas electrode measure the total (ammonia + ammonium) when the solution is alkaline (>11pH) This electrode is a monovalent anion type.
628IS (Ammonium) Electrode
At 7pH most of the ammonia/ ammonium is in the form of ammonium, hence the importance of the ammonium ion selective electrode , operating at 7pH.
606IS (Calcium) Electrode
The pH should be between 4 and 10 pH. This electrode is a divalent cation type.
605IS (Chloride) Electrode
This electrode is stored and shiped dry. This electrode is a monovalent anion type.
603IS (Nitrate) Electrode
This electrode is a monovalent anion type.
