Product category:
Liquid Analysis: pH, Conductivity, ISE
News Release from: Metrohm UK | Subject: Unitrode and storage
Edited by the Processingtalk Editorial
Team on 25 February 2008
How to extend the storage life of pH
electrodes
The best way to extend the life-span of your titration or pH electrode, is to use the Metrohm Unitrode and storage solution - Using cheap electrodes can be a false economy
Investing in a Metrohm high specification Unitrode electrode and Metrohm storage solution will result in many working hours of dependable titrations and pH measurements no matter what your application is The Metrohm Unitrode sensor (6.0259.100) has been designed for a multitude of different applications
This article was originally published on Processingtalk on 2 Jul 2008 at 8.00am (UK)
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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 specialized U-glass membrane which has been developed to have a very low alkali error and temperature resistance.
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The fixed sleeve diaphragm on the electrode is far superior to the standard ceramic pin diaphragm because:.
* 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 100ul/h.
* Virtually insensitive to contamination and blockages.
* 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 6.2323.000 Storage Solution (patent pending) 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. Request a free brochure from Metrohm UK ...
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