Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Extend the life-span of your electrode
Article Type: Methods From: Anti-Corrosion Methods and Materials, Volume 55, Issue 4
Investing in a Metrohm high-specification Unitrode electrode and storage solution will result in many working hours of dependable titrations and pH measurements, no matter what the application. Cheap electrodes can be a false economy The Metrohm Unitrode sensor has been designed for a multitude of different applications.
This combined pH glass electrode has a fixed ground-joint diaphragm, the large surface area of which ensures the sensor is insensitive to blockage by particulates or contamination. In addition, the glass membrane of the Unitrode electrode is suitable for most conditions including high alkali and is resistant to high temperatures. This is because they are made from a specialised U-glass membrane which has been developed to have a very low-alkali error and temperature resistance.
The fixed sleeve diaphragm on the electrode is far superior to the standard ceramic pin diaphragm because of the following:
optimised geometry of the ring-shaped diaphragm increase electrolyte flow having a favourable effect on the measurement;
improved signal stability improves measurement;
reproducible electrolyte outflow of around 100 μl/h;
virtually insensitive to contamination and blockages; and
diaphragm design eliminates any effect of differing stirring speeds.
Normally, a combined pH glass electrode is only stored in c(KCl)=3 mol/L because it is then immediately ready for use without prior conditioning of the diaphragm. However, long-term storage in KCl solution damages the glass membrane and causes increased response times. For the pH glass membrane the optimal storage medium would be distilled water, but after such storage the diaphragm would have to be conditioned for several hours.
The new electrode storage solution has been developed to solve this very problem. If a combined pH glass electrode is kept in this solution then the performance of the glass membrane does not change with respect to the response time and the alkali error. If c(KCl)=3 mol/L is additionally used as the reference electrolyte then the optimised composition of the storage solution guarantees that the pH glass electrode is always ready for immediate use.
Conditioning prior to the measurement is not necessary, no matter how long the electrode has been stored. Therefore, by replacing your cheap ceramic pin diaphragm electrode with a Unitrode and storage solution will reduce the number of electrodes you get through and may turn out to be more cost-effective in the long-run.
For further information please visit the web site: www.metrohm.co.uk