Chromatography Forum

I'm having significant RI baseline issues. I'm not used to this specific detector, mobile phase or column or HPLC so I am not sure if it's detector issue or if it's due to some other issue or if it's "normal" (which i doubt. It's been a long while since I had dome much with an RI... and way back when it was GPC work not Carbohydrate quantiation.

I'm using an Infinity 1260 with a binary pump and the 1260 RID

My mobile phase is ACN/Water 80:20 (premixed). The column is a 150 mm Agilent Carbohydrate column. Both the RI and column are are to 38C. Because of the noise level I'm getting HORRID sensitivity. The noise looks to be about 1000+ nRIU from peal to peak!

I would appreciate any suggestions!

Thanks!

Here is What I am seeing:

Have you tried purging your reference cell with your current mobile phase?

If this were my problem, the first thing I would do is shut the pump off and measure the baseline noise under static conditions. That will pick up any lamp stability or electronic problems.

Assuming everything is OK there, burp the reference side as suggested by mardexis.

You're running a pre-mixed mobile phase, which should eliminate any pump proportioning issues, but be sure that both inlet lines are in the same reservoir and are fully primed.

Check the user's manual and see if there is a procedure for cleaning the sample side of the flow cell. That pattern (or lack of pattern!) is consistent with either a small air bubble or a piece of particulate garbage wandering around in the flow cell.

I found the problem... Even though there was no visible leak the problem was with the pre-column cartridge holder. once I took that out everything was fine (I'm injecting some standards without it). I'm guessing one of the cartridge holder end caps was a tiny bit loose and there was a tiny leak.

When I put it back in and make sure everything is tight, if it happens again I'll know there is an issue with is the holder and order another.

Thanks all,
- Karen