acetonitrile and check-valves

[lmh]

I'm struggling with an elderly Surveyor MS pump (Thermo). It's started to have what looks like check-valve problems (pistons move, no pressure, if I open the purge line, liquid goes in and out; same on all lines, so it can't be a GPV issue, happens in mid sequence when pressure has previously been stable, so I don't think it's a sudden bubble; forcing liquid forwards through pump usually frees it, and it starts pumping OK again, but not for ever...). This has happened at a time someone is pumping fairly high rates of 100% acetonitrile to degunk their column after making injections of samples that contain something hydrophobic that otherwise accumulates on column. Failures tend to happen correlating with their 100% acetonitrile clean-up runs. But the pump is also 10 years old... (although obviously maintained, with regularly-changed check-valves; this problem has happened on 2 sets of check-valves, one new, one of dubious history).

(1) Does anyone else have experience of this sort of problem on that pump?
(2) Is it likely to be an acetonitrile-with-check-valves problem?
(3) If so, is it possible to use a mix of acetonitrile and methanol as an alternative strong organic clean-up, without check-valve problems?

Thanks in advance for any comments and help.

[Csaba]

Hi all,
It was an article about this in one of the papers a couple of years ago. Yes 100 % acetonitrile increases the problem with the valves significatly so although it is more mork. It is better to have 95% Acn + 0.1 TFA + 5% water intead of 100 % Acn etc. It also depends on the quality of Acn because the problem is due to deposition of impurities on the balls. High quality checkvalves will have MORE problems since they require less deposit before they glue together. Ultrasonification of the valves in formic acid-water helps to clean them. Hope it helps.

[Johnny Rod]

I forget the details but many Waters systems had problems with check valves when using acetonitrile. Do a search on this forum, there were different/updated valves which worked a lot better.

[bisnettrj2]

lmh:

I have no experience with the Surveyor pump. You've probably identified the culprit, however. My thought while reading your thread was to mix acetonitrile and methanol, even before I got to your suggestion. It can't hurt to try. Maybe 90:10 acetonitrile:methanol?

Alternatively, you can attempt the cleaning process in the manual:

http://sjsupport.thermofinnigan.com/tec ... re_RFS.pdf

If that fails, you might want to consider changing to ceramic ball-and-seat check valves from Optimize Technologies. They claim that these check valves work better with high acetonitrile applications than ruby check valves.

https://www.optimizetech.com/part/OPTI% ... rmo-L-Pump

[Gerhard Kratz]

If the ball is an rubin ball and you clean the check valve in an ultrasonic bath with for example ACN or Isopropanole, please take the rubin ball in your fingers and roll it to get some "dirt" on it. Sounds strange, but it will work.

[lmh]

Thanks all! Much appreciated.