Acquity columns background contamination?

[guira]

Hi all
I'm a new user of UPLC-QTOF (synapt) i'm having really huge background contamination by polisiloxanes (m/z 610, 684, 758,.. in positive ESI) after just 20 runs using BEH C8 and HSST3 columns and a mobile phase of acetonitrile:isopropanol:water (0.1% formic acid)
Is this normal for these columns/mobile phase? would it be better to change the columns?
It would be really nice to hear from user of this equipment about their experiences

[Uwe Neue]

How did you store the columns?

[guira]

columns were stored in acetonitrile+10%water (without formic acid)
I'm afraid isopropanol cannot be used with these columns, but I'm not sure, am I right?

[Uwe Neue]

I did not check on the MW of your contamination. Assuming that it is related to hydrolysis of the surface, it it due to the storage of the columns with water. We recommend to store the columns in 100% acetonitrile, which stops all hydrolysis.
On the other hand, if the contamination is from the hydrolysis, it should be easy to eliminate it after a few blank gradient runs from 10% organinc to 90% organic.
There is nothing wrong with using IPA with these columns. IPA is completely innocuous.

[guira]

Thanks for your help!!
G.