Analysis of Residual Volatiles in Recycled Polyethylene Terephthalate

Optimization of Ti-BA efficiently for the catalytic alcoholysis of waste PET using response surface methodology

A titanium benzoate (Ti-BA) catalyst was prepared by hydrothermal method, which has an ordered eight-face structure, and was used for polyethylene terephthalate (PET) depolymerization. With bis(2-hydroxyethyl)terephthalate (BHET) as the target molecule and ethylene glycol (EG) as the solvent, the best reaction conditions for catalytic alcoholysis via a PET alcoholic solution were investigated via response surface experiments and found to be a EG/PET mass ratio of 3.59, temperature of 217 °C and reaction time of 3.3 h. Under these conditions, the amount of the catalyst required was only 2% of the mass of the PET, and the yield of BHET reached 90.01% and under the same conditions, the yield of BHET could still reach 80.1%. Based on the experimental results, the mechanism of alcoholysis, Ti-BA catalyst activated ethylene glycol deprotonation to achieve the progressive degradation of polymers. This experiment provides a reference for the degradation of polymer waste and other transesterification reactions.

Determination of potential volatile compounds in polyethylene terephthalate (PET) bottles and their short- and long-term migration into food simulants and soft drink

Head space (HS)-GC-MS was used to analyze possible migration of volatile compounds from polyethylene terephthalate (PET) bottles for soft drinks, and a total of six compounds were identified. Next, a rapid, simple, and accurate simultaneous method was established using purge-and-trap (PT)-GC-MS, to quantify their amounts in the liquid contents after short- and long-term storage in PET bottles. Starting with brand-new PET bottles, the maximum migration of 2-methyl-1,3-dioxolane into distilled water and 50 % aqueous ethanol after 2 years at 25 °C were 2.3 and 19 ng/mL, respectively. In commercially available bottled mineral water sold inside and outside Japan, we were able to detect 2-methyl-1,3-dioxolane in the same way. While nonanal was also detected in some products, 2-methyl-1,3-dioxolane was confirmed as the main volatile compound. Finally, the human exposure to 2-methyl-1,3-dioxolane was estimated based on the per capita intake of soft drinks in Japan and the migration amount in this study.

Reducing off-Flavour in Commercially Available Polyhydroxyalkanoate Materials by Autooxidation through Compounding with Organoclays

Polyhydroxyalkanoates (PHAs) are nowadays considered competent candidates to replace traditional plastics in several market sectors. However, commercial PHA materials exhibit unsatisfactory smells that can negatively affect the quality of the final product. The cause of this typical rancid odour is attributed to oxidized cell membrane glycolipids, coming from Gram-negative production strains, which remain frequently attached to PHAs granules after the extraction stage. The aim of this research is the development of customised PHA bio-nano-composites for industrial applications containing organomodified nanoclays with high adsorbance properties able to capture volatile compounds responsible for the displeasing fragrance. To this end, a methodology for the detection and identification of the key volatiles released due to oxidative degradation of PHAs has been established using a headspace solid-phase microextraction technique. We report the development of nine bio-nano-composite materials based on three types of commercial PHA matrices loaded with three species of nanoclays which represent a different polar behaviour. It has been demonstrated that although the reached outcoming effect depends on the volatile nature, natural sepiolite might result in the most versatile candidate for any the PHA matrices selected.

Determination of Volatile Components from Live Water Lily Flowers by an Orthogonal-Array-Design-Assisted Trapping Cell

A convenient and easy-moving, modified, headspace solid-phase microextraction (HS-SPME) device was developed for monitoring a living plant’s volatile organic compounds (VOCs). It consisted of a polyethylene terephthalate (PET) bottle as a sampling chamber, and certain variables were considered when using the HS-SPME device, including the material used and the fiber position, the direction of the airstream, and the distance between the sample and the fan. The results from varying those factors, generated by the orthogonal array design (OAD) method, were used to optimize the modified HS-SPME conditions. Based on the current literature regarding extracting fragrances by SPME, we selected polydimethylsiloxane/divinylbenzene (PDMS/DVB) and polydimethylsiloxane (PDMS) as the fiber materials. Using the OAD method, PDMS/DVB was found to be the better fiber material when it was parallel to the fan, and also when the airstream provided positive pressure to the sample with the fan near the sample. The device was used to sample biogenic volatile compounds emitted from fresh Nymphaea caerulea (water lily) flowers, followed by gas chromatography-mass spectrometry (GC-MS) analysis. For the method validation, under the optimum conditions, the calculated detection limit value of the model compound (butyl decanoate) was 0.14 ng on column, which was equal to 1.41 ppm for the injection. The relative standard deviations of the intra-day and inter-day precisions were 1.21% and 3.05%. Thirty-three compounds were separated and identified. The main components in the vapor phase of N. caerulea were benzyl acetate (10.4%), pentadecane (15.5%), 6,9-heptadecadiene (40.1%), and 8-heptadecene (15.3%).

Determination of volatile organic compounds in exhaled breath of heart failure patients by needle trap micro-extraction coupled with gas chromatography-tandem mass spectrometry

The analytical performances of needle trap micro-extraction (NTME) coupled with gas chromatography-tandem mass spectrometry were evaluated by analyzing a mixture of twenty-two representative breath volatile organic compounds (VOCs) belonging to different chemical classes (i.e. hydrocarbons, ketones, aldehydes, aromatics and sulfurs). NTME is an emerging technique that guarantees detection limits in the pptv range by pre-concentrating low volumes of sample, and it is particularly suitable for breath analysis. For most VOCs, detection limits between 20 and 500 pptv were obtained by pre-concentrating 25 ml of a humidified standard gas mixture at a flow rate of 15 ml min^-1. For all compounds, inter- and intra-day precisions were always below 15%, confirming the reliability of the method. The procedure was successfully applied to the analysis of exhaled breath samples collected from forty heart failure (HF) patients during their stay in the University Hospital of Pisa. The majority of patients (about 80%) showed a significant decrease of breath acetone levels (a factor of 3 or higher) at discharge compared to admission (acute phase) in correspondence to the improved clinical conditions during hospitalization, thus making this compound eligible as a biomarker of HF exacerbation.

[Validation Study on Headspace-GC Analytical Method for Residual Volatile Substances in Food Contact Polystyrene and Its Application for Surveillance (1998-2014)]

A headspace-GC analysis method for the determination of residual volatile substances (styrene, toluene, ethylbenzene, isopropylbenzene and propylbenzene) in food contact polystyrene (PS) was evaluated. Ten PS products were analyzed by this headspace-GC method and the Japanese official method, and the values obtained were almost equal. The performance of the method was evaluated, and the trueness, repeatability and reproducibility were 100.4-102.8%, 3.7-6.3% and 6.0-11.1%, respectively. The values of the performance parameters of the headspace-GC method fulfilled the requirements, and this method was confirmed to be extremely precise. Moreover, contamination of the GC equipment was minimized. The residual volatile substances in 58 PS products were surveyed with this method. All products met the specifications defined in the Japanese Food Sanitation Law, and no relationship was found between volatile substances and the sampling year or country of origin.

Metals in Recycled Polyethylene Terephthalate and Discrimination Method for Its Use

Metals in recycled polyethylene terephthalate (PET) were analyzed by ICP-MS following microwave digestion with nitric acid. Physically and superclean-like recycled PET contained both Ge and Sb, and sometimes contained Co, P or Si. In contrast, the chemically recycled PET contained only Ge or Sb, and some samples contained Co. The recycled PETs did not contain Pb or Cd. Ge and Sb were catalysts of the polymerization, and the other metals also originated from the PET resin as additives. It was concluded that there is no safety concern about metals in recycled PET. It became clear that the presence of both Ge and Sb could identify products formed using physically or superclean-like recycled PET. According to this discrimination method, about half of the sheet molding products used recycled PET.

Analysis of Formaldehyde, Acetaldehyde and Oligomers in Recycled Polyethylene Terephthalate

Formaldehyde (FA), acetaldehyde (AA) and oligomers in recycled polyethylene terephthalate (PET) were analyzed by HPLC. All of the physically recycled PET contained detectable levels of FA, AA and oligomers, and the levels were almost the same as in used bottles. Most superclean-like and chemically recycled PET contained lower levels than new pellets. These compounds showed no decrease upon physical recycling, but showed a marked decrease upon superclean-like recycling. In PET sheets made using physically recycled PET, FA was decreased, though AA was increased by the sheeting process as same as new one. FA, AA and oligomers originated from PET resin and their levels in recycled products were almost equivalent to those in new products. It was concluded that there is no particular safety concern about their presence in recycled PET.