Aldehyde DNPH derivatives and GCMS

[mspera]

Can 2,4-dinitrophenylhydrazone derivatives of aldehydes, particularly that of formaldehyde, be quantified using GCMS? We have a GCMS and are looking into analyzing raw materials and products for their formaldehyde content. I see numerous papers and test methods which specify HPLC. Are the DNPH derivatives unstable to high temperatures? I know they can be used for melting points, but will they survive a 275 C GC inlet?

[James_Ball]

The other question would be if DNPH has a low enough boiling/melting point to be used in GC. It may not be volatile enough.

EPA Method 556.1 uses PFBHA 0-(2,3,5,6-PENTAFLUOROBENZYL)-HYDROXYLAMINE HYDROCHLORIDE as a derivitizing agent for GC/FID which should work for GC/MS also.

[rb6banjo]

You will likely struggle with 2,4-DNPH derivatives and GC - even for formaldehyde.

I've used this and solid-phase microextraction to get H2CO:

https://www.sigmaaldrich.com/US/en/prod ... ich/194484

The idea was to load up a fiber (CX/PDMS) with reagent by exposing a fiber to the headspace of an aqueous solution of the reagent. Then, remove it and expose it to the sample for X amount of time. The derivatives are amenable to GCMS. I just used a flame but you could use MS. The trouble I had was that you can't get a tremendous amount of the reagent on a small SPME fiber so I had to expose the sample to the loaded fiber for very brief times (15-20 seconds). Otherwise, I risked running out of derivatizing agent on the fiber. In the end, I was able to determine H2CO in plywood with that procedure.

[soccerdad007]

I am not sure if you have the capability to do headspace but we used this method in past with reliable results
https://resources.perkinelmer.com/lab-s ... dehyde.pdf

Kevin

[mspera]

Thank you all for your helpful responses. I will need to investigate this further.

[csiquet_flex2000]

Hello everybody,

For my very first post, I will be commenting on this one year old topic as it is very similar to what I'm trying to do.

I managed to come up with a GC-FID method to separate and detect DNPH-propionaldehyde derivatives and I was trying to devise a quantification method.
My problem is that, according to this article, aldehydes (except formaldehyde) and asymmetric ketones will produce two isomers when derivatized and the ratio of the cis/trans isomers might be light dependent.
It would not be a problem if the response factors of the isomers were the same but they should be different.
So far, it seems the ratio has been mainly the same. I even injected a solution before and after sun exposure. The ratio stayed the same but the signal was lower (this suggested the solution is not stable to light).

Would you have a suggestion on how to procede with a quantification method?
I usually do external standard calibration curves with added internal standard but I'm really puzzled on how to consider the possibility of having a variable isomers ratio.

Thank you.

[Consumer Products Guy]

We investigated this as well, and our conclusion was that DNPH derivatives of formaldehyde and glutaraldehyde were best assayed by HPLC.

[csiquet_flex2000]

We investigated this as well, and our conclusion was that DNPH derivatives of formaldehyde and glutaraldehyde were best assayed by HPLC.

Thank you for the answer.

Indeed, according to the article I mentioned, HPLC is better suited for this analysis. If the correct wavelength is selected because the isomers have different absorption spectra.
The thing is, the peak for DNPH-propionaldehyde is not too well resolved from the matrix with our LC method. Further development is needed I guess.

Alternatively, I could use GC-MS I believe.
The difference of response factors seen in GC-FID should not be a problem in SIM mode.
Am I wrong?

[csiquet_flex2000]

Can 2,4-dinitrophenylhydrazone derivatives of aldehydes, particularly that of formaldehyde, be quantified using GCMS? We have a GCMS and are looking into analyzing raw materials and products for their formaldehyde content. I see numerous papers and test methods which specify HPLC. Are the DNPH derivatives unstable to high temperatures? I know they can be used for melting points, but will they survive a 275 C GC inlet?

Just leaving this here for reference:
GC-FID - Application News from Shimadzu (Nº G327A)