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Noise or disturbance in the base line
Posted: Fri Oct 13, 2006 9:33 am
by gregorjose
Details of my process.
System Agilent 1100
Mobile phase 0.1% TFA in purified water
Gradient
Temperature maintained at 40 Degrees
For the last one week I am observing small peaks(noise) in my blank runs ( runs with out any sample injection but with a gradent). I tried washing my system with IPA, Methanol, hot water etc. It is not helping at all. I changed the UV lamp and used a new column, still it is showing noise. System is passing the gradient test.
Help me....
Posted: Fri Oct 13, 2006 10:58 am
by PJ8
Could you describe the symptoms a little more. Are you seeing the odd sporadic peak or continuous oscillation of your baseline which looks like a series of small peaks?
If the latter is the case then your problem is likely to be with the mixing of A & B in the pumps (easily diagnosed by monitoring the blank at 100% A or B and seeing if oscillation goes away.) If your run is gradient you would see the oscillating baseline decrease as the proportions approached 50:50.
Posted: Mon Oct 16, 2006 7:34 pm
by Tobias Jonsson
Poor quality of the purified water is a common source of strange peaks during blank gradient runs. Try a different source of water or try to vary the equilibration time. If the sizes of your small “noiseâ€
Posted: Mon Oct 16, 2006 9:45 pm
by Mark Tracy
TFA has the property of amplifying minor ripples in the solvent composition. High-pressure mixing gradient pumps are especially prone to this effect at the low-organic end of the gradient. This is because the residence time in the gradient mixer is shorter than the cam cycle of one pump when it is pumping <10% of the total flow. You can check for this by cutting the concentration of TFA in half; your noise peaks will decrease by half also.
Thanks
Posted: Wed Oct 25, 2006 4:13 am
by gregorjose
I found out the problem in my system. I think some proteins were getting deposited in the flow cell. I cleaned it with tissue paper and given a longer wash with hot water. My base line is very clear now.
Thanks to all...
Posted: Wed Oct 25, 2006 8:42 am
by HW Mueller
Did you take the cell apart to clean it with tissue on the inside, or did you have protein leak onto the outside.....? (I would be affraid to touch the optics with some tissue, do you have special material?)
Just wonder how much longer you washed the cell with hot water compared with the earlier hot water wash (which didn´t show improvement).