Isolation, Characterization and Structural Elucidation of Polybutylene Terephthalate Cyclic Oligomers and Purity Assessment using a 1H qNMR Method

Abstract

The use of polybutylene terephthalate (PBT) as a food contact material is increasing over the last years. Typical contaminations in the final PBT product include its cyclic oligomers, which are allowed as additives in food contact plastics according to Regulation (EU) No. 10/2011.Their investigation is currently limited by the lack of analytical standards and physical-chemical information. Therefore, four PBT cyclic oligomers have been isolated and purified from a PBT raw material with an automated preparative HPLC-DAD system. Comprehensive characterization of the compounds was performed using Ultra-High Performance Liquid Chromatography (UHPLC) with high resolution time-of-flight mass spectrometry, Fourier-Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Nuclear Magnetic Resonance (NMR) spectroscopy. The purity of each oligomer was assessed using a 1H qNMR method and ranged from 96.1% to 97.0% for PBT tetramer and trimer respectively. The availability of pure and well characterized PBT cyclic oligomer standards will facilitate future studies of release from plastic food packaging materials.

Analysis of PBT and PET cyclic oligomers in extracts of coffee capsules and food simulants by a HPLC-UV/FLD method

“…Other options for isolating oligomers from FCM polymeric materials include the drastic complete dissolution of the PES followed by precipitation of the polymer and recuperation of the oligomers ( Tsochatzis et al, 2019b ). In order to select the extraction solvent for the study here, the following points were considered: For comparability reasons the same solvent should be used with the three extraction techniques; Ethanol proved to be an efficient alternative to chlorinated solvents in the ASE extraction from PES ( Alberto Lopes et al, 2018 ); The use of chlorinated solvents can improve extraction yields of oligomers, but this effect is expected to be more significant when high oligomeric amounts are present in the polymer; The dissolution technique may lead to potential misleading results if the polymer degrades into its oligomers during the process ( Tsochatzis et al, 2019c ). …”

“…The dissolution technique may lead to potential misleading results if the polymer degrades into its oligomers during the process ( Tsochatzis et al, 2019c ).…”

“…10/2011 ). The PBT oligomers were in-house characterised and checked for purity, which was found to be 96% w/w or higher ( Tsochatzis et al, 2019c ). All chemical information for the PET and PBT cyclic oligomers is given in Table S1 of the supplementary information .…”

Synthesis, Characterization and Properties of Biodegradable Poly(Butylene Sebacate-Co-terephthalate)

“…The intensity of the C–H peak was the greatest for PBSe, while that of PBT was the weakest. Specifically, strong peaks were detected at 2919 and 2851 cm −1 in the spectrum of PBSe; the intensity of these peaks weakened with increasing DMT content [ 38 , 39 ]. PBT exhibited three low-intensity peaks corresponding to C–H stretching (2962, 2915 and 2848 cm −1 ).…”

Food Contact Materials: Migration and Analysis. Challenges and Limitations on Identification and Quantification

“…Polyester cyclic oligomers have been identified in food simulants and extracts from FCMs, ranging from linear to cyclic structures, presenting a diverse spectrum of physico-chemical properties, e.g. molecular mass, octanol-water partition coefficient (logK ow ) [ 4 , 5 , 6 ]. The lack of commercially available oligomer standards, and the lack of mass spectra libraries are a trivial downfall to this direction, as it hinders their confident analytical identification and quantification into food, food simulants or FCMs [ 3 , 5 , 7 ].…”