Chromatography Forum

I have two DAD detectors which are giving high baseline noise than they used to and it's now interferring with peak integration, causing the SSTs to fail.

I have changed the lamps (more than once) and have seen no improvment. The noise is still there even when I remove the flow cell so the rest of the HPLC system can be taken out of the equation.

I tried cleaning the windows and even exchanged the entire optical unit and saw no change. Although it didn't look like electrical interference noise I tried moving the system and that made no difference either (besides, the two troublesome units are in different rooms and there's no problem with neighbouring systems).

I haven't run an ASTM noise test as it's not running Chemstation so I haven't worked out how to do that through their Chromeleon software without running a whole PQ, however the undulations have an average height of 0.02mAU which is out of spec (should be <0.01).

Any ideas? I'm going to try taking the main board out and cleaning up the contacts but to be honest I'm not holding my breath with that solution...

Thank you.

Any chance you could post a picture of the noise and is it short term noise or a cyclic change in the baseline?

thanks
Mike

The noise is there all the time. I guess it's short-term... it's not really even enough to be considered cyclic but it's certainly constant.

Unfortunately I can't see the image. Probably thanks to our paranoid IT department.
As it is short term noise, and you can see it without the flow cell in place and you have replaced the optical unit and the lamps, I would think it is due to an electrical fault contributing to the dark noise of the system.

regards
Mike

Hi

The Agilent spec for ASTM noise through chemstation is 0.05mAU, if you are getting an average peak height of 0.02mAU then you would pass.

The noise is there all the time. I guess it's short-term... it's not really even enough to be considered cyclic but it's certainly constant.

Unfortunately, I am was also was not able to inspect your problem in detail. But you should always take in conclusion, that sometimes problems come from the VIS-Lamp.

I had the same problem on a G1315A. Also exchanged the optical unit without any improvement of the baseline. Eventualy I changed the mainboard, which helped! The idea behind changing the mainboard is: when the mainboard becomes "old" it interferes with the powersupply of the lamp. So the lamp gives an inconsistent ammount of energy which results in a noisy baseline.

hello,

Before changing the mainboard, i will clean lenses, holmium filter and i will rebuilt the flow cell.
All procedures are detailled in the operator manual, and it's not so diffucult to do.

If it doesn't works, you can try to change the mainboard.

good luck,

Pierre