Peristaltic pump in the chromatographic analysis of the pressure display value is high and low, irregular phenomenon analysis
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At this point, it is necessary to carefully check whether the valve under the infusion tube and the pump head is tightened, whether the PTFE tube has cracks, etc., because the liquid will generate a slight negative pressure when flowing, and the air will enter the system.
After checking the confirmation, turn the vent valve counterclockwise for about one turn, then press and hold the traversing button. At this time, the pump flows out from the venting valve at the highest flow rate, and the air bubbles flow out.
This phase must be performed when the pump head has been cleaned or when the mobile phase has been replaced.
When the effect of this method is not good, the pressure cap of the valve on the main pump head can be loosened a little (about one-third of a turn) and the air bubbles in the check valve can be eliminated.
When the instrument is newly purchased or not used for a long time, sometimes such a phenomenon occurs. When it is confirmed that the infusion tube is all normal, the above situation is also outdated, the effect is still not good, and the pump can be operated for a period of time to achieve the purpose.
This is because the gem valve ball and the seat surface are not fully wetted by the mobile phase, and the sealing is not strict during the liquid absorption and drainage processes, and the backflow phenomenon causes the pressure and flow rate to be unstable.
For the mobile phase, full degassing (ultrasonic) is required. It is best to use the current degassing. Do not leave it for too long, otherwise the air will slowly dissolve into it. The bottle containing the mobile phase should not be exposed to direct sunlight. It is best to place it in a higher position (higher than the pump), but it is difficult for bubbles to enter the system (bubbles rise).