Proper Replacement of Moisture Analyzer Electrolyte
The electrolyte of the Karl Fischer moisture analyzer requires two reagents in the determination, one is the coulometric anolyte, and the other is the coulometric catholyte. The two reagents are separated by a septum to prevent the two reagents from interfering with each other.
Iodine is generated in the anode chamber of the titration cell, and the generated iodine reacts with the moisture in the sample. The anolyte can oxidize the iodide ions in the anolyte under the action of an electric current, so it can be said that the anolyte is a variant Karl Fischer reagent.
The catholyte is a reagent completely different from the anolyte, so not just any anolyte can be added to the cathodic chamber for analysis, otherwise the reduced product reduced by the catholyte may permeate into the anode chamber through the diaphragm, making iodine The ions are oxidized causing the measured result to be higher than it actually is.
Pay attention to the following points when replacing the electrolyte
1. Prepare a clean filter paper, put the two drying tubes of the electrolytic cell on the paper, take out the electrolytic electrode, pour out the electrolyte in the cathode chamber (electrolytic electrode), and then put the anode chamber (electrolytic cell bottle) Pour off the electrolyte solution slowly (be careful not to slip the stirring bar into the sewer).
2. If the electrolytic cell is not polluted, it does not need to be cleaned. Strict operation must be followed when cleaning.
3. Cleaning: including the electrolytic cell bottle, electrolytic electrode, measuring electrode, and stirrer, it can be cleaned with anhydrous methanol, ethanol and other anhydrous solvents; after cleaning, dry it in an oven below 60°C for 4 hours, and then dry it in the oven naturally cool down.
Note: When cleaning, the two plugs, wires and rubber caps should not touch the cleaning solution.
4. On the measuring electrode, two drying tubes, the sampling cock, and the grinding port of the sealing port, evenly apply a layer of vacuum grease and install it on the corresponding position, and turn it slightly to make it better sealed. Inject about 120 ml of electrolyte solution into the cathode and anode chambers respectively. Keep the liquid level in the cathode and anode chambers consistent, and the liquid level should reach the lower scale line of the electrolytic cell. Then install the sealing plug and drying tube, and turn it slightly to make it better sealed.
5. The color of fresh electrolyte is brown red or brown black. The color is light yellow in normal use.
6. Failure of the electrolyte: the following conditions may fail.
(1) The electrolyte has been used for more than one month;
(2) The color of the electrolyte becomes darker (in the non-iodized state);
(3) The electrolysis process is difficult to reach the end and also after shaking the electrolytic cell several times.
(4) Artificial iodine production is very slow.
7. During use, due to high air humidity, frequent sampling or difficulty in reaching the end point when making solid samples, shaking the electrolytic cell between experiments can make it reach the end point faster.
8. Note: Be careful when changing reagents. Do not inhale or touch the reagents with your hands. If you come into contact with the reagents, rinse them thoroughly with water. Because the reagent smells strong and contains toxic ingredients, the laboratory should be well ventilated.
