Determination of Volatile Organic Compounds in Recycled Polyethylene Terephthalate by SPME/GC ¡Á GC£­QTOF MS

KeyWord:recycled polyethylene terephthalate£¨rPET£©  comprehensive two-dimensional gas chromatography£­quadrupole time of flight mass spectrometry  volatile organic compounds  method optimization

Abstract:

      Polyethylene terephthalate£¨PET£© is an excellent material for recycling due to its low diffusivity and low sorption features£®The ideal recycling is to use the recycled PET£¨rPET£© material for the initial intended use£®There are some intentionally added and non-intentionally added risk substances in rPET£®There will be some safety risks if these substances migrate into food£®Due to insufficient data on rPET pollutants for safety assessment£¬rPET cannot be used in food contact materials in China£®In this study£¬a method was established for the analysis of volatile organic compounds£¨VOCs£© in rPET using comprehensive two-dimensional gas chromatography£­quadrupole time-of-flight mass spectrometry£¨GC ¡Á GC£­QTOF MS£© combined with headspace solid phase microextraction£¨HS-SPME£©£®Influences of different SPME fibers£¨PDMS£¬DVB/PDMS and DVB/C-WR/PDMS£©£¬extraction temperatures£¨50£¬70£¬90£¬110£¬130£¬150 ¡æ£©£¬headspace equilibrium times£¨15£¬30£¬60 min£©£¬modulation periods£¨2£¬4£¬6 s£© and heating rates of oven£¨3£¬5£¬8£¬10 ¡æ/min£© on the determination effect were compared£®The VOCs were identified with NIST library combined with Kovats indexes£®The content of high-frequency compounds was determined by semi-quantification£®The best HS-SPME and instrument conditions were as follows£ºSPME fiber£º80 ¦Ìm DVB/C-WR/PDMS£¬extraction temperature£º110 ¡æ£¬equilibrium time£º30 min£¬modulation period£º4 s£¬and heating rate of oven£º8 ¡æ/min. 209 volatile organic compounds were determined in 9 rPET samples£¬including aromatic compounds£¬alkanes£¬alcohols£¬aldehydes£¬ketones£¬esters£¬olefins£¬naphthalene£¬carboxylic acids and phenols£®Aromatic compounds could be derived from the degradation of rPET in different environments£®Terpene may come from the residue of flavor substances in early PET bottle drinks£®Among the 9 rPET samples£¬the substances with detection frequency greater than 5 were d-limonene£¬¦Ã-terpinene£¬5-methyl-1-undecene£¬tetradecane£¬naphthalene£¬1-methyl-naphthalene£¬1-ethylidene-1h-indene£¬2-dodecanol£¬2-decanone and 2£¬4-di-tert-butylphenol£®D-Limonene is a common pollutant in rPET£¬which comes from the contact between original PET bottle and beverage£®2£¬4-di-tert-butylphenol may be the degradation product of antioxidant 168£¬and remaining in rPET£®The highest content of high-frequency compounds was 2.13 mg/kg£¨tetradecane£©£®No misused compound with extremely high concentration was found£®This research provided not only a scientific and reliable methodological basis for the investigation of VOCs in rPET£¬but also the basic data for utilization and safety assessment of rPET.