Agilent 1100 - Sinusoidal baseline

[t_morris]

Hello,

I am running on a Agilent 1100, and continue to get a sinusoidal wave with a period of about 13 min. I don't know where to go as I have already changed the pump seals. I don't see a leak anywhere in my system and my pressure is stable with fluctuations within 1 Bar. Any help is appreciated.

Thanks,

Tim

[tom jupille]

What detector?

[t_morris]

UV currently set at 277nm.

[bisnettrj2]

What column temperature? How well do you control the room temperature? Is there an A/C vent blowing on the instrument?

Also, try this - remove the flow cell, replace the cover, and start a run. See if the problem persists. If it does, it's optics or lamp related.

[tom jupille]

Another (admittedly less likely) possibility is that you are seeing the effect of a slight variation in composition (by the way, an out-of-alignment flow cell will exacerbate this). You can check for that by pre-mixing your mobile phase and then putting *all* of the solvent intake lines in the same jug.

[KM-USA]

We just recently had a similar issue on an Agilent 1200 system essentially the same, but this had DAD detector and wavelength of 280nm.

First we isolated that it was NOT the pump (we set flow to zero or shut off pump). The repeating pattern remained, sure seemed like it was detector-related, not related to flow at all, did not change. Then we turned pump on but slid the detector flow cell out, still repeated.

Unfortunately, we do not yet have Lab Advisor software, so we couldn't run a lamp diagnostic test, or even see how many hours the lamp had been on in its lifetime (the system came from a different department).

So I installed a new old-stock UV lamp (from May 2008, never used), ran the system overnight, and I've since run another sequence and no issues.

So - for us - so far it seems like it was an old lamp. Notice that I said "so far".

[LCbob]

As bisnettrj2 has said most long period sine waves on detectors is caused by air conditioning temperature changes. Agilent's early DAD ( G1315A ) were very prone to this until Agilent put a heater by the optics bench ( G1315B+ ).

[t_morris]

Well...
The detector # is the G1315A-DAD. I have removed flow cell and am still seeing the sinusoidal curve. I have replaced lamp and no change. I will try to insulate the device, but we haven't changed the room's temperature setting so I don't know what else to do now...

Could there be a bad relay/fuse for the fan in the detector? If so how would I determine that...it is currently running on chromeleon 6.8.

Thanks again

Tim