Analysis of Hexanoic acid in alcoholic extracts.

[ProfessorRabbit]

Dear all,

I have to find a procedure for the analysis of hexanoic acid in ethanolic or methanolic solutions.

I think that I have to derivatize the molecule, but have no experience with derivatization procedures. Are Silylation reagents suitable for ethanol or methanol solutions? Is there a good procedure for derivatization in alcoholic solutions?

How to prepare standards for calibration if no derivatized standards are available? Also derivatize the standard solutions?

regards,
ProfRabbit

[krickos]

Hi

No, you should not have to derivatize hexanoic acid. There several examples of chromograms including instrument settings at supplier sites without it (for example Agilent).

A FFAP or INNOWax column (30m*0,25mm* 0,25µm) may be used to analyse/separate your acid.

[ProfessorRabbit]

Hi,

unfortunately it is not only Hexanoic acid, but also other compounds like dicarboxylic acids, phenols, glycols, non-saturated acids...

And I have only one GC/MS System running. It is used all day with a conventional column.

regards,
ProfRabbit

[krickos]

Hi

Well that may limit your options abit

Is still "only" hexanoic acid the intresting part or all the others too?

As for standards, several methyl esters of acids are commercially availeble, for instance at FLUKA including the methyl ester of hexanoic/Caproic acid.

If the acid is the only intresting one, BCl3-methol 12% solution would proberly work, generates a methyl ester of the acid fairly quickly.

Suppliers like fluka/supelco etc have a bunch of good booklets/pdfs on their sites where you can read up a bit on dervatisation.

[Consumer Products Guy]

I have to find a procedure for the analysis of hexanoic acid in ethanolic or methanolic solutions.

You'll likely find that some/most of the hexanoic acid has already esterified with the alcohol(s) in situ before you get the sample. We used to assay for hexanoic acid in fatty acids using GC after trimethylsilyl derivatization using C7 fatty acid as internal standard. Hexanoic acid methyl or ethyl esters are pretty volatile. Are you looking for "free" hexanoic acid" or total "free and combined" ?