>In the case of this type of measuring device so-called ion-selective membranes are used which will only allow a specific target ion through. In an electrochemical measuring loop, consisting of the membrane and a reference electrode, an electrical potential is built up in this way across the membrane that is dependent on only one target ion. The concentration resulting from this can be calculated using the Nernst equation.
Advantages of these measuring devices:
They are usually designed as probes so that they take measurements directly in the medium and no longer require the samples to be treated.
They are relatively small, with the result that measurements can be taken using them even in difficult places.
The running costs are low as no chemicals are required.
The investment costs are considerably lower than in the case of an analyser.
The Disadvantages:
> The devices must be calibrated on a regular basis.
They cannot be used in all types of wastewater.
They do not yet achieve the accuracy of analysers.
At present, it looks as though this technology is becoming more and more widespread and is becoming a competitor to analysers that has to be taken seriously. In the last few years our research group has gained a lot of experience with regard to this technology in various projects.
