Alginate

[timjm]

Hello All:

I am currently trying to determine the ratio of mannuronic acid to guluronic acid in a sample of alginate. Both are carbohydrates.

Alginate itself is a linear unbranched polymer containing b-(1-4)-linked D-mannuronic acid (M) and a-(1-4)-linked L-guluronic acid (G) residues.

If I have pure samples of D-mannuronic acid and L-guluronic acid, would I be able to determine their ratio in alginate using LC?

Thanks in advance for the help.

[Kostas Petritis]

Normally yes...

Assuming that you have the right LC conditions (i.e. both of your acids are separated among themselves and other impurities contained in the alginate).

Do you want to determine the ratio of these acids after you hydrolyse somehow the alginate? What do you intend to use for their detection?

[timjm]

Kostas:

Thanks for the quick reply.

I'm really shooting blind as to determing the m/g ratio of my alginate. I was just trying to find an approach, and was considering either NMR, HPLC, or mass spec.

Have you determined the m/g ratio with LC before, and if so, how did you accomplish it. More specifically, did you hydrolyze your alginate, and do you need controls?

Thanks.

[Einar Ponten]

Why don't you try ZIC®-HILIC?

That will most likely solve your problem.

[Kostas Petritis]

If you have the monomers of your polymer then you are able to know their response factor and make a calibration curve. I would first inject the non-hyrolysed alginate to see if it contains any of the monomers (as impurities).

Then, you need to hydrolyse your alginate (I have no idea with what) and be somehow sure (maybe with SEC) that you have hydrolyse it about 100%. You should be able then to calculate the ratio of your monomers.

[Chris Pohl]

timjm,

I'm quite certain these compounds can be separated readily by anion exchange. For example, one can readily separate glucuronate and galacturonate on an IonPac AS11 column using a hydroxide eluent system. I don't have ready access to mannuronate and guluronate, though but if you send me a sample of each analyte I can have someone here do a quick separation for you.