Determination of volatile and semi-volatile model contaminants in recycled high-impact polystyrene from food-contact applications. Comparison of extraction by purge-and-trap, co-evaporation, and total dissolution

Poly(ethylene terephthalate), Poly(butylene terephthalate), and Polystyrene Oligomers: Occurrence and Analysis in Food Contact Materials and Food

Polyesters (PES) and polystyrene (PS) are among the most used plastics in the production of food contact materials (FCM). The existence of compounds that could migrate from these materials into food requires a constant analytical control to ensure the safety of consumers due to consumption. It also implies a significant research challenge for their identification and quantification. One of the most important groups of known FCM migrants are the substances known as oligomers. PES and PS oligomers have long been suspected to possess some toxicological effects. The International Agency for Research on Cancer and the European Food Safety Authority alerted recently to the potential carcinogenicity of styrene, with its oligomers consequently being also in the spotlight. At the same time, PES cyclic oligomers are categorized as having Cramer III toxicity. Many recent works on the occurrence of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and PS oligomers in FCM and food have been published. The oligomeric chemical analysis requires the use of demanding analytical strategies to address their different physicochemical characteristics (melting points, octanol/water partition coefficients, and solubility properties). Chromatographic methods are normally preferred due to the intrinsic complexity of the target matrices, but the reduced amount of reliable analytical standards still hinders the widespread screening analysis of oligomers in food. This work presents the most relevant recent studies and analytical methodologies used in the analysis of PET, PBT, and PS oligomers in food and FCM, as well as current and future challenges.

Development and validation of a fast gas chromatography mass spectrometry method for the quantification of selected non-intentionally added substances and polystyrene/polyurethane oligomers in liquid food simulants

A simple, fast, sensitive and reliable method was developed for the simultaneous determination of 13 food contact materials (FCM) regulated substances and non-intentionally added substances (NIAS) migrating into official food simulants. The method has been optimized to quantify the monomers styrene and α-methyl styrene, selected polystyrene oligomers (dimers, trimers) and polyester urethane-based oligomers (PU) cyclic oligomers, as well as cyclic NIAS originating from food packaging such as 2,6-Di-tert-butylbenzoquinone and 7,9-Di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione. The method employs liquid-liquid extraction of aqueous ethanol food simulants with dichloromethane, and analysis with gas chromatography coupled to mass spectrometry (GC-MS) with a total analysis time of less than 16 min, with limits of detections ranging from 0.32 ng mL^-1 (1,1-diphenyl-ethylene) to 14.8 ng mL^-1 for 7,9-di-tert-butyl-1-oxaspiro[4.5]deca-6,9-diene-2,8-dione and respective limits of quantification from 1.0 ng mL^-1 to 41.7 ng mL^-1, for the same analytes. Accuracy and precision results showed that the method is sufficiently accurate for all target analytes, with recoveries ranging between 80 and 110% and relative standard deviations (RSDs) smaller than 16% at the three selected concentration levels. The method has been successfully applied to seven FCM. Results indicated that significant amounts of polystyrene monomers, dimers and trimers are migrating into food simulants; this is also the case for polyester urethane-based oligomers (PU). Exposure assessment estimation was performed using EFSA's approach on the total sum of migrating oligomers. In certain cases, amounts of PS and PU oligomers found to be in some cases higher than the respective limits, for the sum of oligomers with a MW lower than 1000 Da.

Efficiency of whole and skimmed powdered milk for trapping volatile compounds released from plastic containers in high-temperature applications

Plastic food containers used for high-temperature applications are not completely inert, and potentially harmful chemicals may be transferred to foodstuffs when such containers are heated. The aim of this work was to investigate the role of food fat content on the efficiency of trapping volatile organic compounds from heated plastic packaging. Relatively simple food matrices such as powdered skimmed and whole milk were evaluated with respect to their retention of several selected migrants: toluene, 1-octene, ethylbenzene, o-, m-, and p-xylene, styrene, and 1,4-dichlorobenzene released from containers made of polypropylene (random and copolymer), polycarbonate, and styrene-acrylonitrile copolymer, which are all commonly used in high-temperature applications. The analytical method (purge and trap gas chromatography and mass spectrometry) was optimized for each matrix. The developed procedure had detection limits of 0.01 to 1.2 ng, depending on the analyte and sample matrix, and both reproducibility and repeatability (expressed as relative standard deviation) were below 15%. This method was applied to the different plastic materials. The concentrations of the volatile compounds in both matrices were well below the established specific migration limits. Temperature and fat content of powdered milk were the most influential variables in mass transfer processes. These values were compared with those obtained with either Tenax TA (alternative test medium for fatty food simulants) or Porapak Q (another widely used sorbent). Similar results were found in skimmed powdered milk and Tenax TA, but significant differences were observed for whole powdered milk.

Use of new generation poly(styrene-divinylbenzene) resins for gas-phase trapping-thermal desorption

Two new generation polymeric resins, Bond Elut ENV (styrene-divinylbenzene) from Varian and LiChrolut EN (ethylvinylbenzene-divinylbenzene) from Merck, commonly used in liquid--solid-phase extraction (SPE) were evaluated as sorbents for gas-phase sampling followed by thermal desorption and compared to Tenax TA, a reference sorbent in this kind of applications. The three resins were tested against seven volatile organic compounds (VOCs): 1-octene, ethylbenzene, (p-, m-, o-)xylenes, styrene and 1,4-dichlorobenzene. Elution curves for all compounds were determined at temperatures from 120 to 180 degrees C, and from such curves, different parameters, such as retention factor (k), distribution coefficient (K), height equivalent to a theoretical plate (H), asymmetry factor (Fa) and breakthrough volume (VB) were calculated and extrapolated at room (25 degrees C) and desorption (220 degrees C) temperatures in order to estimate breakthrough and elution volumes. In average, retention in LiChrolut EN is 10 and 200 times stronger than in Bond Elut ENV and Tenax TA, respectively, but its chromatographic behavior is rather poor giving quite asymmetric elution profiles (Fa >1.8 at 120 degrees C). Bond Elut ENV exhibited the best chromatographic behavior, with H values two or five times lower than those of LiChrolut EN or Tenax TA. An additional advantage of the new sorbents is that retention decreases with T much faster than it does in Tenax (8 or 20 times for Bond Elut ENV or LiChrolut EN). Modeling has finally shown that beds with 60-80 (for Bond Elut ENV) or 300-400 (for LiChrolut EN) times less of sorbent have the same retention properties than standard Tenax TA tubes and similar (LiChrolut EN) or five to six times smaller (Bond Elut ENV) elution volumes. These predictions have been experimentally confirmed.