Chromatography Forum

Hello,

I am trying to measure formaldehyde levels by GC using a FFAP column and TCD. Analysis of a pure sample appears fine -- but I just found out that the actual sample I will be provided contains formaldehyde reacted with sodium hydroxide. In theory, all of the NaOH will be converted to methanol and sodium formate and I need to measure the remaining unreacted formaldehyde. I am wondering if this sample mixture (sodium formate, in particular) will be problematic or damaging to the GC? Additional method details: Inlet temp 250 C with packed injection liner, TCD 200 C. I'm fairly new to GC and just want to be sure that I don't ruin anything by trying this sample! Thanks for any guidance.

Depending upon how much water is present a certain amount of NaFormate will be converted to formic acid. This in itself does not pose a problem for most GC columns.

But any salt (such as NaFormate) has little or no vapor pressure. If it doesn't vaporize it will not elute from the injector or the head of the column when deposited during injection. Formaldehyde generally reacts when heated and forms dimers and trimers of itself, if not with other analytes in the matrix.

Reaction with Diphenylhydrazine and HPLC analysis will probably be a much more reproducible and accurate determination. You may see NO formaldehyde by GC but that doesn't mean it wasn't there to begin with.

I have been burned too many times trying to measure formaldehyde as formaldehyde by GC. It just doesn't work.

Best wishes,

Rod