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Agilent odd noise
Posted: Fri Oct 14, 2011 5:45 pm
by sepscientologist
My 1100 has a sudden increase of noise on both UV and RI. Pumping via quaternary pump 10 mmol sulfuric acid.
Trying these various things caused no change in the observed sinusoidal noise signal.
*Take out/put in column (7.8 x 50 Hform ion exclusion)
*Turn on/off degasser
*Turn on/off UV (obviously the UV signal went away when off but no change on RI
*Turn on/off column heater (set at 60C)
The sinusoidal signal is observed on degasser/pump channel D. When using channel C I observe more random noize
of about the same amplitude and period. Really bizarre. Any thoughts?
Re: Agilent odd noise
Posted: Fri Oct 14, 2011 8:43 pm
by tom jupille
It looks like the frequency just about doubles when you double the flow rate, so suggest something like an air bubble or a wheezy check valve. If you can get a pressure profile, that might give more information.
Another possibility is a partial blockage or leak inside the degasser so that you end up aspirating some air during the intake stroke (that's consistent with different results on the different channels). Bypassing the degasser entirely should confirm/deny that.
Re: Agilent odd noise
Posted: Mon Oct 17, 2011 7:41 am
by LCbob
Hi
First off can I suggest you overlay the Pump pressure plot to the DAD plot, this will indicate whether it is a pump problem. My only concern at this moment is the period is very long for a check valve issue.
It would be nice to know what pressures you are running at with the column in place. Also have you just set this method up on this system or has it been running fine for a while.
Re: Agilent odd noise
Posted: Mon Oct 17, 2011 11:31 pm
by sepscientologist
The pressure is rock solid. It is a flat line at around 40 bar at 1 mL/min. I replaced the UV lamp and oddly noise on both RI and UV seem fine
on the degasser/solvent channel I am using. Running a glut of samples but will check the other channels when I get a break. For now it is working
but I wouldn't imagine that a bad UV lamp would affect the RI detector. Thanks!
Re: Agilent odd noise
Posted: Sun Oct 23, 2011 6:13 am
by chakri36
Hi i Agree with others to isolate problem with pump but one moreimportant thing is
1. Agilent recommend not to Mutli channel Gradient valve in line when using RI detector , the line from from Solvent bottle has to go directly to AIV whci is below the pump . this is the best way to isolate your problem(You can isolate Degasser also).
2.Use premix if you want to use two solvent mix