Chromatography Forum

Hi all I have never worked with an RID before. I would like to try it for Steviol glycosides and Mogroside V from monk fruit. They may have possibly enough sensitivity for my purposes at UV210 (with 10ul injection on a 1260HPLC running water acidified with H2SO4 down to pH 2.5/CH3CN I can get 10ppm in the standards probably ~50ppm samples.

What temperature should I set the RID at. Should it match the column temperature? The column separation is high temperature at 60 deg C. Is it far enough from the column (It passes through the DAD first I believe just to control it at 30 deg C or whatever).

I'd try setting RID at 60C. And I'd insulate the tubing connecting to the RID.

RI often has VERY long equilibration times and poor sensitivity, but IS worth a try if you have the detector.

Try this free article with tips on how to best use a RID inline.

"HPLC Baseline Stabilization Tips for Refractive Index Detectors (RI or RID)"; https://hplctips.blogspot.com/2018/02/h ... s-for.html

RI often has VERY long equilibration times and poor sensitivity, but IS worth a try if you have the detector.

Try this free article with tips on how to best use a RID inline.

"HPLC Baseline Stabilization Tips for Refractive Index Detectors (RI or RID)"; https://hplctips.blogspot.com/2018/02/h ... s-for.html

I am doing a lot of work on artificial sweeteners. Steviol glysocides (working with Rebaudioside A, D, M and stevioside) and monk fruit mogroside V have a pretty poor sensitivity on UV even at 210nm, worse than the other 210 analytes potassium acesulfame, aspartame, and neotame. I can get down to 1ppm with those and in standards I get down to 10ppm with steviol glycosides running a gradient with acetonitrile and water acidified to 2.5 with H2SO4. But in samples there are all these random peaks and noise making it problematic even to get to 100ppm which are cleaned with carrez. I am planning to try RID to see if it is any better.

In my system, after the column, the line goes through the DAD then to the RID so by then the flow has probably cooled so the column compartment temperature is not relevant.

Ok thanks I just read the article. I adjusted my method to 50degC column temperature to resolve a coelution so I will try 50deg for the RID.

I just read a bunch of old articles about bypassing the gradient mixing valve to get a more stable RI baseline. I am a bit confused how to do that. I see there is an adapter mentioned 0100-1847 that takes 10-32 to 1/4-28 at the AIV.

My 1260 has a bunch of larger diameter ptfe tubes going from each degasser channel to the MCGV. All the fittings are Peek finger tights. Then, in the center, a smaller diameter Ptfe tubing comes out and goes to the inlet valve. Could I plug that smaller sized ptfe tubing into the degasser or should I take the larger diameter ptfe tubing coming from the degasser and run that to the AIV with the previously mentioned adapter ferrule. I think all the threads on the MCGV are 10-32 so I would think the former.

edit:
Nevermind I found the answer and a picture in an old thread. I need the adapter and to plug the larger diameter tubing coming from the degasser into it and the AIV.
https://www.chromforum.org/viewtopic.php?t=102284

At our lab, folk were confusing adapter 0100-1847 with some fingertight fittins we used.

So I taped plastic sandwich bag to the sides of our unit and put the adapter into that when not in use (1050 and 1100 units).

Well I managed to get the RID to stabilize. I had to make a new bypass tube as all the existing tubes were not long enough they were just long enough for their usual paths.

I cut some PTFE solvent tubing put those flangeless fittings with the tefzel hat shaped grommet and the steel rings and put that into the detector.

I set the column temperature to 55 deg C and the RID to 50 because it has a very weak slow heater and despite having a maximum temp of 55 it really struggled to get above 50.