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Beginners Guide to ISE Measurement, Chapter 15.
LOOKING TO THE FUTURE

Further developments are well advanced. It is likely that in the near future the range of the interfaces will be increased to include other sensors such as dissolved oxygen and conductivity. It must be noted, however, that conductivity may not be possible for simultaneous measurements with other sensors in the same solution, because of the interference caused by the alternating current which has to be applied to these electrodes.

Other developments will be to extend the range of the interfering ion corrections to other ion pairs, or even multiple interferences. One limitation to this may be that in some cases it may be necessary to make separate calibration nets for particular electrode combinations in order to achieve acceptable results, and this may prove to be an un-economical proposition and destroy the cost-advantage of using this technology in preference to others.

Unfortunately, for some interferences, it will never be possible to make any compensation or correction. For example, the silver electrode cannot be used in the presence of sulphide and vice verse. This is because the same silver sulphide crystal membrane is used for both electrodes. Thus it is equally sensitive to both the positive and negative ions in the solution and the potentials will tend to cancel one another. There is no way of overcoming this problem as long as this same crystal is used for both ions and this will always be a limitation on the use of the silver and sulphide electrodes. A similar situation exists for cyanide and iodide. In these cases the only solution will be to develop new membranes which are more specific for particular ions.