Pay attention to the following points when choosing to buy:
After the end point is reached, it also needs to be manually closed. 1 When selecting, Zui should consider the automatic type instrument. Manual moisture analyzers require the tester to visually inspect the reagents in the glass burette. Delays due to different people's habits can lead to unnecessary errors.
The ethyl ester sample to be tested and the methanol solvent should also prevent errors in the air from being dissolved. 2 When choosing a moisture analyzer, consider purchasing a fully enclosed test system. The bare Karl Fischer reagent absorbs moisture very easily because of the presence of iodine.
The Karl Fischer reagent is a highly corrosive reagent, and 3 should consider the life of the metering pump. The metering pump is a key part of the volumetric moisture meter. Metering pumps made of corrosion-resistant materials such as fluoroplastics should be purchased as much as possible to prevent leakage and cause the instrument to be scrapped.
On the one hand should have a higher sensitivity, 4 electrode problem. This part is a core part of the moisture analyzer. On the other hand, because it was soaked in the test cell during the test, Zui chose to equip with a high-quality platinum electrode instrument to adhere to the electrode life.
To get accurate test results, in addition. In addition to strict operation in accordance with the procedures, the moisture analyzer should also pay attention to the following problems:
From the reagent bottle to the metering pump to the reaction cell, the system is completely closed. The local connection of the Karl Fischer reagent fluid circuit must be tightened. Otherwise, reagent leakage will directly affect the test results. Another problem with its non-sealing is that the Karl Fischer reagent absorbs air moisture during the test, which causes a delay in the titration end point.
Try to use a 10ul sampler and sample the exact problem. 10 mg of water is required to calibrate the Karl Fischer reagent. This is not only accurate and fast, but also prevents water droplets from sticking. Similarly, the use of methanol reagents, ethyl esters have similar problems, should pay attention to minimize the opening time of the reaction tank after the transfer.
Since the titration reagent is added locally, the magnetic stirring speed is adjusted. In the reaction cell. It is not in one place with the electrode, so the stirring speed is so fast that it does not form turbulence, so that it can reach the end point quickly.
When the strain is slow near the end point, the titration speed should be set first and then slower. The titration is fast to minimize the test time. This improves metering accuracy.
Be sure to empty the Karl Fischer reagent in the system and after the test on the day. Then clean with methanol, do not wash the system with water, because it is not easy to volatilize, will cause the Karl Fischer reagent calibration is not true in the next test.
To prevent the electronic display from jumping during operation, the moisture analyzer should be kept away from strong magnetic fields. An abnormality has occurred. Manual moisture analyzers, because it is necessary to use a glass automatic burette to measure Karl-Fischer reagent and methanol solvent, and the glass burette itself must be connected to the outside due to the equilibrium pressure.
When used, in addition to the above aspects that need attention. You should also pay attention to the following two points:
In order to reduce the interference of air moisture on the test results. When the relative humidity of the air is greater than 70%, the system should be sealed as much as possible. A manual moisture analyzer requires a U-tube filled with a desiccant on the suction pipe and the glass burette. Try not to arrange a moisture test.
Zui is adjusted to 1 drop/second. Too fast a titration rate will result in a large delay error when reaching the end point; while a slow titration speed will lengthen the test process and adjust the titration rate of the burette. The above interference is likely to cause delay to reach the end point.
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