An analytical method for formaldehyde, acetaldehyde and cyclic oligomers in polyethylene terephthalate (PET) products was improved. PET samples were dissolved in trifluoroacetic acid in the presence of 2,4-dinitrophenylhydrazine to derivatize formaldehyde and acetaldehyde to their dinitrophenylhydrazone derivatives. After neutralizing with aqueous K
2CO
3, the solution was filtered under reduced pressure to remove the precipitated PET, then extracted with dichloromethane to obtain the derivatives along with the PET cyclic oligomers. The derivatives and PET cyclic oligomers were analyzed using HPLC with UV detection at 360 nm and 254 nm. They could be identified by LC/MS. Recoveries of 76.9〜101.2% were obtained for a PET pellet sample (0.5 g) spiked with formaldehyde (2.5μg), acetaldehyde (2.5μg) and PET cyclic oligomer (trimer, 1.8 mg). Using the analytical method described herein, it was determined that PET food packages contained formaldehyde (ND〜1.38μg/g), acetaldehyde (11.57〜44.43μg/g) and PET cyclic trimer (3.6〜10.9mg/g).
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