[lexi7_]

i'm having trouble with this FTIR spectrum i took of an "unknown" polymer, and i'm not sure what the (double) peak at 2360 is supposed to represent?

i searched online and only found CO2, but based on TGA and DSC analysis performed on the polymer i should have PET, so CO2 doesn't make any sense? so yeah i'm a bit lost

[rjb]

Hi Lexi,

CO2 (from the atmosphere) is a distinct possibility...
How are you creating your background and could you purge with something like nitrogen maybe?

R 

[wildfyr]

100% certain its CO2. Its from you or others breathing nearby after backgrounding it. You raise local CO2 slightly.

This PET sample is not in good contact with the ATR crystal, which is the reason for poor quality. But after backgrounding it, quickly load sample and try not to breathe on it if the sample chamber is opento the air