Chromatography Forum

Hej,
We have got a request to analyze formaldehyde, formic acid and methanol from aqueous samples at concentrations around 10 to 500 uM. Concentration range is too low for our normal organic acid method (ion exclusion) and I was wondering if there is a way to derivatize these different functionalities either for HPLC-UV or GC-MS in water solution? If possible, I would prefer to stick with one method for these three analytes.

I know that formaldehyde can be derivatized and analyzed by HPLC-UV, not too sure about methanol and formic acid along with formaldehyde though.

Hi

Is example 2 in this article using GCMS of any help?

http://www.shimadzu.com/an/industry/new ... e0zdh.html

Your lower limit of 10uM for methanol would, for example, be approximately 0.3 ppm.

Regards

Ralph

That's a tough call to quantify them all in one run. Here is what worked well in our hands"

Sampling: SPME with Carboxen fiber at around room T
GC: Porapack-Q column starting at around 0C. Need to hold at 0 for about 2 min.

MS: Use isotopically labelled targets as IS. Monitor pertinent ions in SIM mode.

LLOQ: From low ppm to tens ppb depending on matrix: These are ions common for a lot of compounds.

This sounds like a good approach

Regards

Ralph

You can derivatize the formaldehyde and formic acid but not the methanol (easily). Acetyl chloride in acetone works quite well for GC and GC-MS methods.

Methanol at 0.3 ppm is going to be tough no matter what method you use.

If you've got a good UV/vis spec, you could probably set up an enzyme-coupled assay for methanol using alcohol dehydrogenase and following appearance of NAD(P)H (340nm, roughly 6.2 mOD units per uM solution with a 1cm path-length).