Chromatography Forum

Hello all,

We have several Waters 2690/2695 HPLCs and we have had a horrible time with check valve failure (both sticking open and close). Some of the problems may be due to analyst error using buffer and then organic and precipating out, but even after or annual PMs we have had instances where the check valves have seen nothing but Methonal and Water and then they have fouled within a week.

Our latest problems have been caused by people using an ACN mobile phase modified with phosphoric acid. It seems that even if the percentage of phosphoric acid is small (in this case 0.01%) then for some reason with the ACN it is causing the check valves to foul. This is not limited only to our waters instrument we had a Shimadzu (with passive check valves) go down yesterday using the same mobile phase formula.

Has anyone else experienced problems with their waters check valves and does anyone have any suggestions to remedy the problem? We are changing check valves sometimes several times a year on one instrument which gets costly. Also, all anlysts are trained to rinse the system with water after they use a buffer and then all analysts store the system in methanol when it is down.

I appreciate you help.

Jason

I had this problem in the past with old Waters and Gynkotek systems. Phosphate is very problematic, indeed.

The only solution is to either change your buffer system or use the same mobile phase without buffer (just deionized and filtered water + ACN) to wash the column overnight.

Most ruby ball/sapphire seat type check valves encounter problems running straight ACN. If you insist on running straight ACN and mixing on-line, I suggest using ceramic core cartridge check valves instead. This goes for Waters, Shimadzu and others.

The frustrating thing is that we have also tried Water's ceramic check valves as well as Optimized Technologies check valves and we have not found that they are any better. Our LCs are not dedicated to a particular person so they see lots of different mobile phases, but we rinse everything appropiately and store the systems in methanol so I believe it is not something we are doing, but I could be wrong.

Just a brief survey...if you have a Waters 2690/2695 how often do you change the check valves? And how frequent is the instrument in use?

I want to see what the "industry standard" is with this problem.

Thanks,
Jason

We get ours changed yearly, our LCs see a couple hundred samples per week (give or take a couple hundred ).

I know people that never changed their check valves and other that changes it every month...

I think, as with your car, you should schedule timely maintenance and stick to it...

Thanks you guys...We have our LCs on an annual PM cycle but I know we have seen some sporadic problems with our check valves that I am having trouble explaining. For example, on some systems they will last the entire year until the next PM. On most systems they foul sometime or many times during the year. I know that all of this could depend on the mobile phases that our analysts use on the LC, but what I really can’t explain is that a few times I have changed them while I was performing the PM and then in the next couple days of testing they will fouled they had only seen methanol and water.

I had this problem only extraordinarily and generally at use mobile phase with acetonitirile or with perchloric acid as ion-pair. I changed valves every once in a while (once a year or bi-early). I use PerformancePLUSâ„¢Check Valve Cartridges (700000254) no Check Valve Cartridges (WAT270941).

For elimination this problem you can try:
a) Use on-line vacuum degaser always.
b) All mobile phases must be filtered through 0.45 µm filter
c) In case of valves problem, the first action is wet prime with water and then with acetonitrile and with water again. Then with appropriate mobile phase again.
d) If the problem continues, I remove appropriate valve and clean/flush the valve with water and propan-2-ol (ultrasonic bath is possible). The repalce of valves I carry out under flow of solvent (not GPV turn off).