Most Karl Fischer Moisture Analyzers use a polarized double platinum electrode to measure the voltage. After a period of use, "some Karl Fischer reagents and samples will invalidate the electrode response." End point recognition delay "to the end The color becomes brown instead of yellow. At this time, the electrode must be cleaned. When cleaning, generally put the electrode into an ultrasonic cleaning tank with deionized water or ethanol for several minutes; or put it in chromic acid for 60s '' and then clean with deionized water or ethanol (dry before use).
Types of contaminants and their cleaning methods.
Contaminant type cleaning agent
Fatty oil blend of chloroform and toluene
Polar material dimethylformamide
Salt carbohydrate formamide
Resin polymer substance alcohol acetone ether
Pigment-like substances
(3) Under normal circumstances, the `` drift value of the instrument is a few microliters per minute (referring to the amount of Karl Fischer reagent consumed per unit time to keep the titration cell dry ''; Titration of the water in the titration cell "on the other hand compensates for the consumption of iodine caused by slow side reactions). If the drift value becomes larger, you must check the tightness of the instrument or consider regenerating the molecular sieve. During regeneration, the molecular sieve is placed in a drying furnace at 160-300 ° C for at least 24 hours. The molecular sieve installed on the waste liquid bottle must be washed with distilled water before regeneration because it contains water and sulfur dioxide.
(3) The burette is washed with absolute ethanol solution. Do not place the burette at a temperature above 40 ° C.
(4) The instrument must be placed in a dry and clean environment and arranged for special personnel to keep it; if it is not used for a long time, all reagents in the instrument must be drawn out and all pipes must be cleaned and air-dried.
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