The main reason for this phenomenon is that there are bubbles in the system.

At this time, it is necessary to carefully check whether the infusion tube and the lower valve of the pump head are tightened, and whether the tetrafluorotube has cracks, etc., because when the liquid flows, a small negative pressure is generated at the flowing place, and the air will enter the system.

After checking and confirming, rotate the vent valve counterclockwise for about one circle, hold down the run key with your hand, at this time, the pump flows out of the vent valve at the highest flow rate, and the bubbles flow out.

This phase operation must be performed when the pump head is cleaned or when the mobile phase is 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 the circle).

When the instrument is newly purchased or not used for a long time, sometimes this phenomenon will occur, when the infusion tube is confirmed that everything is normal, the above situation is also outdated, the effect is still not good, let the pump run for a period of time, can also achieve the purpose.

This is because the gem valve ball and seat surface are not fully infiltrated by the mobile phase, and the seal is not strict during the suction and discharge process, resulting in backflow phenomenon causing unstable pressure and flow.

For the mobile phase, it is required to fully degassing (ultrasonic), it is best to use the current degassing, do not place for too long, otherwise the air will slowly dissolve into it. The bottle containing the mobile phase should not be directly exposed to the sun's rays, and it is best to put it in a higher place (above the position of the pump) so that it is difficult for bubbles to enter the system (bubble rise).