Untargeted Screening of Nonvolatile Organic Compounds in Recycled PET Flakes for Food Contact Applications by Ultra-performance Liquid Chromatography£­Quadrupole Time-of-flight Mass Spectrometry

KeyWord:recycled polyethylene terephthalate£¨rPET£©  ultra-performance liquid chromatography£­quadrupole time-of-flight mass spectrometry£¨UPLC£­QTOF MS£©  non-intentionally added substances  untargeted screening

Abstract:

      An ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry£¨UPLC£­QTOF MS£© was established and employed for the untargeted screening of non-volatile organic compounds in washed recycled polyethylene terephthalate£¨rPET£© flakes£®Influences of pretreatment methods including choice of precipitation solvent£¬method of solvent removal£¬amount of test sample£¬and the chromatographic conditions including different mobile phases and eluent gradients on the determination of non-volatile organic compounds in rPET bottle flakes were investigated£®A satisfied results could be obtained by using the following optimized condition or method£º0.2 g rPET flakes was dissolved in 10 mL hexafluoro-isopropanol£¬20 mL methanol was used as precipitation solvent£¬the solvent was removed by nitrogen-assisted evaporation£¬methanol£­0.1% formic acid water system was used as the mobile phase by gradient elution£¬and the data-dependent acquisition£¨DDA£© mode was employed as data acquisition method£®The qualitative analysis on the analyte was carried out by using MS database and secondary spectroscopy£¬while the semi-quantitative analysis was performed using compounds with similar structures£®A total of 30 non-volatile organic compounds were detected in the rPET flakes£¬with amount of 0.038£­4.92 mg/kg£®The detected compounds included 27 types of non-intentionally added substances such as cyclic and linear oligomers£¬by-products of additives£¬degradation and contaminants£¬and the remaining 3 compounds might be associated with intentionally added additives£®The recoveries ranged fron 66.0% to 80.4%£¬with relative standard deviations£¨RSD£© not higher than 5.1%£¬indicating that this method has good stability and repeatability£®24 types of rPET bottle flakes£¨rPET C and rPET N£© from two different geographic manufacturers were detected by the established non-targeted screening methods with principal component analysis£¨PCA£©£®The£¨PCA£© results showed that there were significant differences observed between rPET group C and group N£¬while 15 different types of compounds were detected£®These results indicated that the recycled PET bottle flakes with the same type but having different sources may have different compositions£®The UPLC£­QTOF MS method was demonstrated to be accurate£¬reliable£¬simple and rapid£¬which could be effectively used for the analysis and safety assessment of non-volatile organic compounds in rPET intended for food contact applications.