Anion exchange carbohydrates with RID

[mardexis]

What about analyzing carbohydrates by anion exchange chromatography (ie; pH 13) and RI detection? Assuming the NaOH doesn't destroy my detector is there any reason that would not work well?

Thanks,
Marc

[mardexis]

Hmmm... I was worried about the metal parts but I bet the glass optics in the flowcell would degrade pretty fast too. What if the RI flowcell were plastic coated?

[Bryan Evans]

Is there any particular reason you want to use IEX as opposed
to normal phase?

What sugars will you be working with? What is your sample
matrix?

[mardexis]

I would love to run normal phase with my RID but it just doesn't work that well. Maybe IEX would. The ELSD works fine with normal phase but linearity is much poorer than RI.

[Bryan Evans]

We customers analyzing saccharides on LC-RI using
Unison UK-Amino.

What carbohydrates will you be working with?

[mardexis]

Is that a polymer based amino column like the Asahipak or Alltech Prevail? I don't have any column problems... just detection.

Potentially, all carbohydrates. We are working on biofuels.

[Noser222]

You may find it difficult to get good sensitivity with acetonitrile/water mobile phases and RI detection. The ligand-exchange approach might be better if you're limited to RI since it uses pure water as the mobile phase.

That said, the amino column will definitely give you a lot more flexibility in your mobile phases, but you should consider other options for detection. Evaporative light-scattering might be the best as far as having universal response and sensitivity.
I actually couple the Unison Amino to LC-MS.
If you have UV or fluroescent detectors, consider pre- or post-column derivitization.

[Bryan Evans]

Ok - so your issue right now is with sensitivity -
LC-RI obviously is not very sensitive.

Can you tell us what the end goal of the research is?
I can understand IEX for assaying known analytes in solution.

If your goal is to eventually go to prep (to characterize unknown
saccharides in biofuel) - then normal phase seems more appropriate.

[mardexis]

So, back to my original question... Has anybody run anion exchange chromatography of carbohydrates using RID?


We run ion exclusion now with RID but when we get interferants there is not much you can do.

Typically we are assaying thousands of samples containing known analytes. If I find unknowns I run on the LC/MS for ID.

[Bryan Evans]

Hi Mardexis -

The typical NH2 column is 5um (sometimes polymer based - sometimes silica based).

Unison UK-Amino is 3um silica-based that is durable in aqeuous eluent.
This means you can run a lot of samples - and not worry about loss
of retention (typical problem with silica-based NH2 phases).

Below is a chromatogram comparing our 3um to a typical 5um NH2 phase:
http://www.silvertonesciences.com/files/TI313E.pdf

If you email me - I'll be more than happy to send you more carbohydrate data. Thank you.