nLC flow rate decrease during LC-MS run
Posted: Fri May 10, 2013 9:00 am
Hi all,
I'm wondering if anyone have the same problem with me and hopefully someone out there knows the remedy.
Our nLC-MS/MS system use a Ettan MDLC to deliver a 400-500 nL/min (by split the mobile phase into a 75um ID C18 100A 5um nanocolumn) flow into a ESI source. The gradient start with 5%ACN with 0.1% FA, slowly goes up to 35% ACN in 60 min and then ramp up to 85% ACN with 0.1%FA in 90 min. It works perfect fine when we just inject blanks, but every time we inject a peptide mixture sample, the nLC slowly decrease the flow rate as the sample were separated by the nanocolumn.
We suspect that the sample may contain contaminants, however, we have tried filtration, centrifigation (17000g), C18 spin column/SPE clean up, but those prep method does not help at all.
Is there anyone knows what might be the problem?
Thanks!
Sun
I'm wondering if anyone have the same problem with me and hopefully someone out there knows the remedy.
Our nLC-MS/MS system use a Ettan MDLC to deliver a 400-500 nL/min (by split the mobile phase into a 75um ID C18 100A 5um nanocolumn) flow into a ESI source. The gradient start with 5%ACN with 0.1% FA, slowly goes up to 35% ACN in 60 min and then ramp up to 85% ACN with 0.1%FA in 90 min. It works perfect fine when we just inject blanks, but every time we inject a peptide mixture sample, the nLC slowly decrease the flow rate as the sample were separated by the nanocolumn.
We suspect that the sample may contain contaminants, however, we have tried filtration, centrifigation (17000g), C18 spin column/SPE clean up, but those prep method does not help at all.
Is there anyone knows what might be the problem?
Thanks!
Sun