Chromatography Forum

Hello everyone

I have a problem with my Dionex UV detector: Since yesterday using an eluent with 0.3% formic acid it tells "Invalid baseline data [AZD]" when doing autozero. It was fine the day before. Using other eluents (without formic acid, or less concentrated formic acid) everything is OK. The manual says to check alignment of the flow cell. I don't think this is the cause of this problem, because I would expect decreased sensitivity or higher noise, but other methods still work perfectly.
Any idea (except from lowering formic acid concentration, I really need it )

Thanks a lot
Jörg

Which wavelength do you use?

Formic Acid has a very ugly UV-spectrum < ~230nm

At 254nm it is no problem to use Formic Acid.

Yes, I'm aware of that. Even if I only aquire 250 and 280 it tells the same error message.

Jögr

Hi, Just an idea: It MIGHT be that turning on and off lamp with formic acid in the flow cell is seen by the self-test as too bad to be correct light intensity.
Try to have water/acetonitrile when turning on and off lamp and change to your correct eluent and do a autozero then. Hope it helps.

Thank you Csaba, this did the trick.

Jörg