Mettler moisture analyzer maintenance experience

1. Environmental requirements The instrument specification particularly emphasizes that the air humidity is less than 80%. When the air humidity is greater than 70%, it is found that the balance time has been prolonged. When the balance is used, even the DRIFT (drift) changes, repeated titration, and balance. No, the dehumidifier must be turned on at this time to dehumidify the air and reduce the humidity to less than 70%.

There are three solvent bottles in the moisture analyzer. They contain the titration solution (Karl Fischer), solvent (anhydrous methanol) and waste fluid. Each of the above three solvent bottles has a dryer and a dryer on the instrument. The molecular sieve was placed in all four desiccators (in order to make it easier to observe the degree of water absorption, some discolored silica gel could be placed in the middle, and the new molecular sieve could be replaced by the instructions of the color changing silica gel). The desiccator on the instrument had the greatest impact on the stability of the instrument. Timely replacement, there will also be instrument balance extended, or even the phenomenon of balance can not be. In addition, the instrument's tightness must also be maintained and the instrument stable.

Zeolite regeneration method: baking at 160~380°C for 24 hours, it can be regenerated. In addition, the molecular sieve installed on the waste bottle needs special treatment because SO2 is volatilized in the waste liquid and is also absorbed by the molecular sieve. If it is not treated directly, SO2 will volatilize to pollute the instrument and the environment. Therefore, this molecular sieve should be used. The ionized water is washed several times and then regenerated.

2. The choice of reagents The choice of reagents is very important. The quality of the reagents directly affects the accuracy of the assay and the stability of the instrument. The analysis of moisture in the laboratory is relatively simple. According to the Pharmacopoeia standard, the solvents are all made of anhydrous methanol, regardless of whether the sample is soluble. Methanol. Titrant We chose pyridine-free Karl Fischer titrants (titer greater than 5.0mg/ml), which is the best in the country, but the domestic Karl Fischer titrant has one drawback, that is, the moisture meter is not used for 2 days. The burette inside the burette and the titration solution in the pipette will be delaminated. All the layered liquid must be discharged before use. Otherwise, the accuracy of the measurement will be affected. (Sometimes it may be necessary to eliminate a lot, but for the accuracy of the data, waste The point is worth it).

3. Use of the instrument Before using the instrument every day, first shake the bottle containing the titrant to make it uniform, and then check whether the titration solution flows through the tube for air bubbles, whether it is delaminated, and if so, pass. Drain to remove. Finally, pre-titration and calibration of the titrant (because the titrant will volatilize, the concentration will change, so the latest concentration must be calibrated before use every day to ensure the accuracy of the measured data).

When the titrant is replaced, it is best to use all the previous ones, and then drain the excess and reload the new titrant.