Liquid chromatography check valve cartridge ruby ceramic replacement Waters

When to replace check valve?
① "Lost Prime" appearing when system runs indicates the system pressure is too low, much lower than back pressure required for regular liquid chromatography operation. It mainly is caused by contamination of check valve in pump head, or small bubbles remained in check valve leading to the unsmooth infusion. At this time, what we need to do is to make an attempt to clear out the small bubbles through five-minute operation of "Wet Prime". If this solution fails, we are supposed to remove check valve, and clean it ultrasonically with water above 80℃. It is recommended to replace check valve cartridge if repeated cleaning is ineffective.

② It turns out to that there are bubbles in pump head or check valve when system pressure fluctuates greatly. We can operate "Wet Prime" for 5-10 minutes, to rinse out the bubbles with a high flow rate. If above method does not work, we are supposed to remove check valve, and clean it ultrasonically with water above 80℃. It is recommended to replace check valve cartridge if repeated cleaning is ineffective.

③ When there is a problem with system injection reproducibility, firstly observe retention time. If there a problem with retention time, check the fluctuation of system pressure is normal or not. Normally, at the flow rate of 1ml/min, the instrument's system pressure should be 2000~3000psi. (There are ratio differences depending on the types of chromatographic columns and mobile phases.) It is normal that pressure fluctuation is within 50psi. The balanced and good system pressure fluctuation is within 10psi. Under the condition that pressure fluctuation is too large, we need to consider the possibility that check valve is contaminated or has bubbles, then deal with it.

When to use ceramic check valve?
There is a compatibility issue between ruby check valve of 2690/2695 and certain brands of acetonitrile. The specific situation is: when using 100% acetonitrile, leaving it overnight, and continuing to start experiments the next day, there is no liquid coming out of the pump. This is because the ruby check valve's body and ruby ball have been sticked together after soaking into pure acetonitrile. We should remove the check valve and lightly knock it or treat ultrasonically. When shaking the check valve and hearing a slight sound, this means the check valve returns to normal. Now put the check valve back. The experiments can be normally carried out after 5-minute "Wet Prime".

To avoid this problem in following experiments, it is recommended to use ceramic check valve.