Cleaning of electrodes for cartridge-type moisture titrators
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As the title suggests, I feel that the electrode reactions have become a bit sluggish lately. What is usually used for cleaning them? Experienced sea travelers, please let me know.
The electrodes should be cleaned using acetone, methanol, or other solvents. Note: The electrodes must never be cleaned with water, as this will cause measurement errors when determining the moisture content of the sample.
According to the instructions, it seems that it should be soaked in dilute nitric acid
It can be cleaned with chromic acid solution, followed by rinsing with water, cleaning with ethanol, and drying at 80 degrees
If it’s not severe, it can be cleaned with solvents such as acetone; if that doesn’t work, soak it in dilute nitric acid or chromic acid for about 30 seconds, then clean it with water and organic solvents, and finally blow it dry
The endpoint indicator electrode of a Karl Fischer moisture titrator is generally a double platinum electrode, which also comes in various shapes. When the electrodes become dull, targeted cleaning can be carried out based on the properties of the contaminants. Cleaning solvents can include ethanol, xylene, petroleum ether, etc. When cleaning, you can use a cotton ball dipped in solvent to wipe. Try to avoid using solvents such as strong acids and strong bases for cleaning; firstly, it is not necessary, and secondly, cleaning with acids and bases later on also requires a certain amount of water or other solvents. It cannot be cleaned with aldehydes or similar solvents, as the residual aldehydes can form acetals or other compounds with the methanol in Carls reagent, along with the formation of water. Since this reaction proceeds slowly, it leads to a delay in reaching the endpoint. Additionally, the cleaned electrodes must not be heated and dried, to prevent the platinum wire from expanding and damaging the electrode body. However, the platinum wire of the electrode can be quickly burned with a small flame, which helps to completely remove contamination and improve the sensitivity of the electrode. However, it is not recommended to do this frequently, as it can easily damage the electrodes.
We all use ethanol for cleaning; it’s easy to work with and dries quickly. Tests show that it has no adverse effects, whereas using hydrochloric acid solutions for a long time is harmful to the human body.