FTIR and Terephthalate

[MestizoJoe]

Hi

I am trying to identify the components in a face mask. I observe the presence of polyethylene but I also see a C=O vibration at 1718. The spectral library is saying I have polyethylene, terephthalate but I'm not convinced. Is there some way I can say defininitively if terephthalate is present?

I don't see "benzene finger" in the spectrum either which would be found around 1800. I also don't see CH3 at 1375 nor do I see CH3 vibrations.

[rb6banjo]

Phthalates give a really strong C=O stretch. Is it big? Generally, PE is not plasticized so I'd bet it's something else. For a simple identification, you can do a an extractables test (any solvent other than water, methanol, isooctane, etc.) and analyze for phthalates in the extract by GC. 30 minutes of extraction or so at elevated temperature should do the trick. If quantitation is what you want/need, it'll take some more effort.

FTIR on mixtures must be interpreted with much caution. Usually, you need some other supporting information before figuring out the puzzle.

[MestizoJoe]

Thanks. I'll have to find a suitable gc method for phthalate analysis.

This is part of a medical device and phthalate was te closest library match.

I need to figure out a way to narrow down what this might be.

[rb6banjo]

Mine is like this:

Column: HP-5, 30 m x 0.32 mm x 0.25 µm
Carrier Gas: Helium, @ 25 cm/s with CH4 at 40 °C
Injector: 300 °C, split injection at about 20:1
Column: 40 °C for 2 min., 40-320 °C at 10 °C/min., 320 °C for 10 min.
Detector: FID with standard flows, 320 °C

I inject about 1 µL of extract.

Good luck.