Acetonitrile and piston seals

[AnnP]

We have a GBC pump LC 1120. Since we switched to mobile phase with acetonitrile we are going through piston seals like crazy. They are leaking within a month of changing them. We got 6 months out of them with methanol.

Has anyone else seen this? The company says there are no compatibility issues, but then we are buying the seals from them.

[Kostas Petritis]

Do you have any buffer in your ACN? If yes it might be due to precipitation reasons. If not, that might be harder to figure out. There has been issues with the use of 100% ACN and checking valves (see the link below) but I haven't really heard anything about piston seals...

Another possibility can be if you acidify your ACN and leave the mobile phase for long time without changing it. ACN is polymerizing in acidic pH and the polymer is insoluble in 100% ACN. If this is the case, you can flash your system with warm water (the polymer is soluble in hot water)...


http://www.sepsci.com/chromforum/viewtopic.php?t=3676

[Jackus]

We use high acetonitril concentration mobile phases too. Test different seal material (if possible). For example Agilent offers "black" seals (for RP chromatography) and orange HDPE for normal phase chromatography too.
Regards