Chromatography Forum

We are attempting to develop a method for quantitating inositol via GCMS in a powder mixture that also contains water soluble vitamins and amino acids. The method linked below seems to cover this however we are having a heck of a time getting the inositol standards (and presumably therefore the inositol in the mixture) dissolved in a non aqueous solution. I have tried DMSO, Pyridine, 80:20 ethanol:water - applied heat to all (70C) and still no luck. The concentration I was shooting for with the standard for testing this was 0.1% based on the spike levels utilized in the method.

I want to be able to move this to the derivatization step but without getting inositol dissolved that of course is not going to happen. Any ideas/help is appreciated - here is the method referenced above:

https://academic.oup.com/chromsci/artic ... 631/374225

Did you try just acidified water?

No I did not for this particular issue - I did try the 80:20 ethanol:water as I thought that if it did go into that it could lead to a filter/evap procedure moving forward however based on what I've read (I've never actually done it), trimethylsilylation requires a non aqueous environment. Acidified water will certainly work for dissolving the inositol along with all the other items in the blend but does not get me into a position where the inositol has been further isolated and can be treated further for trimethylsilylation.

Perhaps my 0.1% attempt in pyridine was too high? There has to be something I can dissolve this material in and proceed to the trimethylsilylation step.

Possible solution - Dissolve samples and standards in water - aliquot into pyridine to achieve desired concentrations - initial testing shows that this results in a uniform dissolved sample. Derivatize utilizing TMSI which can tolerate water concentrations up to 40% according to spec however it looks like I should be able to achieve an H2O level of 10% or less.

Open to other suggestions from those with experience with derivatizing carbohydrates such as inositol.

I would try DMF as the solvent, typically what we would use for consumer products, which also contained simple carbohydrates such as glycerin, sorbitol.

Hi

Just a thought. Have you considered or tried just adding the appropriate silylating reagent for inositol to your dry powder and standard?

Regards

Ralph

Thank you for the suggestions. Dissolving in water first, then adding to pyridine at levels that kept the water concentration at 1% prior to derivatization ended up working and we have validated within our specifications.

For sugar and sugar alcohol I like acetates/PAAN peracetylated aldonitrile.

For sugars
add ribitol/aldonitol ITD
blow down
200ul hydroxylamine in pyridine
90 deg 30 min
200ul acetic anhydride
90 deg 30 min
1ml water 0.5ml toluene inject toluene

If all you care about is inositol you don't need the hydroxlamine step go straight to acetic anhydride.