Monday, June 30, 2008

The difference between a pH reference electrode and a double junction electrode is that the pH reference electrode leaks electrolyte solution , thus you will have to replace the electrolyte solution periodically. People who work out in the field can find this procedure inconvenient and annoying. A pH reference electrode is separated from the external junction through which the electrolyte solution leaks. You must replace the lost electrolyte solution by refilling it through the filling hole. If you work out in the field I don't recommend this electrode for you. There is a side effect to refilling the electrolyte solution , it shortens the life of the electrode due to changes in the electrolyte composition, due to the contamination and diffusional leak of the ions. Contaminated gel cannot be replaced, this then shortens the life of the electrode. Rarely does this type of electrode last longer than several months. The Double Junction electrode is sometimes used to prolong the life of the electrode. There is an extra chamber between the reference electrode and the external solution. Before contamination can reach the reference electrode, it must pass through not just one junction but two, which is where we get the name (Double Junction). The extra chamber acts as a buffer, slowing down the changes in the composition of the reference electrode electrolyte. Double Junction electrodes will last longer and that is why they are often more expensive than your Single Junction electrodes. Single or Double Junction only refers to the way a reference electrode is made. So, make your selection wisely when searching for a pH electrode for your pH meter. You may pay a little more for the Double Junction electrode, but you will have less maintenance and it will last you longer!