Analysis of benzoic and salicylic acids

[Andre Orci]

Hi everyone!

Can i perform the analysis of pure benzoic and salicylic acids in an Agilent HP-FFAP column (FID detector)?

If yes, what is the methodology for the analysis (sample preparation, GC parameters...)?

I try to dilute the acids in acetone (3% w/w) but the analysis had a poor resolution.


(I also have an HP-INNOWax column. If this column provides better results than the FFAP, i would like to know the methodology for this one).

[HPLC chemist]

Yes. But HPLC is even better and has replaced thus GC analysis. See attached for GC chromatographic conditions;

https://www.agilent.com/cs/library/appl ... 4582EN.pdf

[Consumer Products Guy]

Yes. But HPLC is even better and has replaced thus GC analysis.

Yes, HPLC using reverse phase and low pH mobile phase and UV detector is typically easier.

But there were instances when we assayed these by GC, but we derivatized with BSTFA and used a non-polar capillary.

[rb6banjo]

I've done this sort of thing by solid-phase extracting them out of the aqueous matrix and derivatizing them with MeOH:BF3. After quenching the reagent with aqueous sodium phosphate, analyze for the methyl esters by headspace SPME.

[Henrylozano]

I've done this sort of thing by solid-phase extracting them out of the aqueous matrix and derivatizing them with MeOH:BF3. After quenching the reagent with aqueous sodium phosphate, analyze for the methyl esters by headspace SPME.

Hello, I think that you can perform one method from direct injection without Derivate any components. Can you send me the list of compounds and I can make one method that you can to essay?

[James_Ball]

Yes. But HPLC is even better and has replaced thus GC analysis.

Yes, HPLC using reverse phase and low pH mobile phase and UV detector is typically easier.

But there were instances when we assayed these by GC, but we derivatized with BSTFA and used a non-polar capillary.

Would derivatizing a 3% solution of benzoic acid require quite a bit of derivatizing agent?

[Consumer Products Guy]

Can i perform the analysis of pure benzoic and salicylic acids in an Agilent (GC using) FID detector?

Would derivatizing a 3% solution of benzoic acid require quite a bit of derivatizing agent?

I think his samples are pure substances. I'd dilute a small amount of sample in DMF or pyridine (my first tries) and then take 250ul and add 125ul BSTFA and mix, then inject.

Even if I had 3% solution in water, I would dilute 0.25 grams sample in DMF or pyridine and then take 250ul and add 200ul BSTFA and mix, then inject. We would use that same sample dilution on samples containing 90% water to assay for analytes 0.1% or lower in the sample.

[MSCHemist]

For esterfication of larger acids I like mild methanolysis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817593/

I've used HCl methanol and done either the overnight 40 deg C or 30 minutes at 90 deg C. It works on diacids like succinic, fumaric etc as well it does hydroxy acids but some give me activity issues with the hydroxyl (citric/tartaric).

[Consumer Products Guy]

Funny, even though we made methyl esters of fatty acids thousands of times, we never bothered for benzoic or salicylic acids.

Like I said before, we ether used BSTFA or simply used HPLC.