Bisphenol A vs. Bisphenol F

[Izabela]

Hello everyone!

I analyze various plastic samples with pyrolysis-gcms. Sometimes I get bisphenol samples. It is difficult for me to distinguish whether a sample consists only of bisphenol F or is it a mixture of bisphenol F and bisphenol A. In the chromatogram of samples with bisphenol F I can always also see peaks with the same mass spectrum as bisphenol A. Is this just a fragment of bisphenol F?

I know that's a very specific area. Maybe someone here knows the topic and can help me?

Best regards,
Izabela

[Consumer Products Guy]

Can you obtain and inject a reference sample of bisphenol F ?

[rb6banjo]

Certainly BPA and BPF don't coelute. I did some work on BPA years ago and found that even my deuterated BPA standard didn't exactly coelute with BPA. I was making acetate derivatives to get BPA by GCMS. While BPA and BPF do have some common masses in their spectra, the big ones are not the same (the ones I would use as qualifiers).

What about using the ratios of isopropylphenol to phenol for BPA and p-cresol to phenol for BPF as a way to sort it out?

[Izabela]

Thank you for your reply!

Unfortunately I cannot be sure that there is no residue of BPA in the BPF reference samples.

The fragments elute one after the other. With such samples, I always have two large peaks that I can identify as bisphenol F and then one with a mass spectrum like bisphenol A. I am not sure whether this is actually a mixture of BPF and BPA or just BPF with a fragment that only looks like BPA.

The decomposition temperature of BPA and BPA is very similar, so I can not separate the bisphenols with pyrolysis GCMS.

Best regards

[Sunny.Singh]

Hi Isabela, Great post. We are currently working on applications in this area. We are using a Frontier lab Pyrolyzer Scion 456 GC and a Scion Single quad mass spectrometer for this application. Could you please reach out using sunny.singh@scioninstruments.com. We might be able to help.

[rb6banjo]

I guess I'm not clear on what you're saying. Is your end goal polymer identification? It might be helpful if you could explain in more detail, what you're trying to accomplish in your measurement.

When you use the term "fragment" in the context of pyrolysis sampling, it could mean how the polymer breaks apart upon intense thermal degradation. In mass spectrometric terms, it means those mass fragments that result because of the sampling introduction into the source of the detector.

If you are analyzing BPA-based polymers, thermal degradation should result in a lot of isopropylphenol and phenol (relatively much smaller amounts of methylphenol). If it is a BPF-based polymer, thermal degradation will result in a lot of phenol and methylphenol (very little isopropylphenol). I believe that Acetone is used to make the bridging carbon between the phenol rings in bisphenolA. That's why it's an "A". Formaldehyde is used to make the bridging carbon in bisphenolF. That's why it's an "F". It is not inconceivable that you might have some residual formaldehyde or acetone in either process and end up with a little bit of one or the other in every sample.

I doubt there's a purely BPA or BPF polymer that you can find, anywhere.

Under pyrolysis conditions, you should be able to use the relative amounts of isopropylphenol, phenol, and methylphenol to sort out if the polymer is F-based or A-based. One or the other pair will predominate in your pyrolysis GCMS traces.

It would be a good trick to make bisphenol-A from bisphenol-F. BPF is a simpler molecule. Is there a way to make BPF from BPA? Perhaps but it seems highly unlikely. Knowing the structures of these epoxy polymers, I just can't see a good synthetic reason for why the methyl groups would leave preferentially and be substituted by hydrogen atoms.

The mass spectra of BPA and BPF are clearly different from each other. Even if they coelute, you should be able to sort your TIC by 107, 183, and 200 for BPF and 119, 223, 228 for BPA and tell the difference. 228-213 = 15 (loss of a methyl group). Phenols typically give great molecular ions in the mass spectrometric detector.

[Izabela]

I identify unknown polymer samples with pyrolysis GCMS. Most of the samples are polyurethane but sometimes I get also epoxy resin and I don’t have much experience with those samples.

I have a few reference samples with Bisphenol A and Bisphenol F. The Bisphenol A samples are easy to identify by comparing them with reference samples.

The problem is for me to identify the samples with bisphenol F. According to the description, the references should contain only bisphenol F. Nevertheless, the results of thermal degradation (pyrolysis 600°C) indicate both phenols (A and F). They are 2,4'-isopropylidenediphenol (m / z 119, 213, 228), methylenediphenol (m / z 107, 200, 202) phenol, isopropylphenol and methylphenol.

I suspected that Bisphenol A was accidentally mixed into the Bisphenol F references or that I was misinterpreting the results.

You are probably right and there are always residue of bisphenol A in the bisphenol F samples.

Thanks for the discussion and tips! It was very helpful!