Hello All,

I'm running biological samples on Agilent 1100 system and Resource Q anion exchance column. Gradient is from

A: 300mM NaCl 50mM Hepes ph 7.5, to
B: 1500mM NaCl 50mM Hepes ph 7.5

followed by

C: 1500mM NaCl 50mM Hepes 1M NaOH, as a clean up for e.g. DNA

I'm seeing variable results for injection precision in my system suitability test. In one run it might be RSD=1% and in another run it jumps to RSD=25% showing a continuously increasing peak area.

I'm a beginner in AEX but I have a reason to believe that my problems is related to flow cell:

-after the run and a quick water flush, the lamp intensity test usually faills. The result is perfect when cell is taken out

-I can clean up the cell after a run. I've got best results by reverse flushing the cell with 1M HCl followed by water

-I've got best inj. precision results after: a) cell replacement, b) extensive cell flush

I don't think that this is traditional carryover because i tried to inject mobile C between my SST injections and I still got an increasing peak area.

Any ideas? Many thanks in advance.

thanks
mikko

ps. why does the threads become locked? some of my earlier problems were resolved and I went there to share the the result but the subject was locked.