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Resoles are multifarious pre-polymeric resins produced by the condensation of basic chemicals phenols, formaldehyde and optionally aliphatic alcohols like butanol. They are widely used as cross-linkers to form resistant internal coatings on metal surfaces of cans, containers or closures. Although the application of resoles is common in food contact, usually little is known about their exact composition, the toxicological hazards of their individual constituents and the migration of phenolic compounds, e.g., of the potentially endocrine-disrupting chemical bisphenol F. Our study fills major gaps of knowledge in risk assessment, using the example of a two-layer polyester-phenol coating system, which is based on three different resoles and is commercially used for closures of infant food glass jars. Various analytical approaches, namely size-exclusion chromatography, nuclear magnetic resonance spectroscopy, liquid chromatography coupled to mass spectrometry, fluorescence and diode array detection as well as gas chromatography-mass spectrometry were evaluated to quantitatively characterise resoles. Additionally, derivatisation with dansyl chloride as well as Folin–Ciocalteu colorimetric assay was adapted first times to determine the total phenol content from technical resoles. Individual mono- and bisphenols were determined in resoles up to about 120 mg/g, while the concentration of bisphenol F isomers was below 10 mg/g. Migration from the coating system was determined after sterilisation (121°C, 1 h, 20% ethanol). Results were ~2 µg/dm2 for identified individual mono-phenols like 2-hydroxybenzyl alcohol and up to ~120 µg/dm2 for total phenolic compounds, representing approximately 7% of the overall migration. The migration of bisphenol F isomers was negligible below 0.3 µg/dm2. Potential exposure to migrating phenols was assessed based on the threshold of toxicological concern concept to be significantly below for individual phenols and in the same order of magnitude for total phenols compared to the respective thresholds calculated for infants.
Linear and cyclic oligomers are unavoidable non-intentionally added substances (NIAS) present in food contact materials made from common polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyester coatings. Although polyester oligomers can migrate into fats in significant amounts in high-temperature processes such as baking or frying, little is known about their toxicological properties and their behaviour in the human gastrointestinal tract. In the present study, first indications of a possible digestibility of polyester oligomers formed from the commonly used aromatic dicarboxylic acid terephthalic acid (TPA) are provided by in vitro experiments. Three cyclic polyester oligomers originated from PET (trimer) and PBT (dimer and trimer) were extracted from the raw materials, isolated and subjected to a simulated intestinal digestion. A fast cleavage (≥75% of the initial amount) of all three cyclic oligomers into their linear counterparts was detected already within the first hour of in vitro intestinal incubation. Subsequent hydrolysis to shorter chained linear oligomers was determined especially for the PET cyclic trimer. Degradation down to the monomer TPA was not observed. In terms of risk assessment and prioritisation for non-evaluated NIAS, the threshold of toxicological concern (TTC) concept is an appropriate tool. While cyclic polyester oligomers based on TPA are assigned to the TTC Cramer class III (high potential concern, exposure threshold 1.5 µg/kg body weight per day), the corresponding linear oligomers are expected to be of a lower probable toxicological concern (Cramer class I, 30 µg/kg body weight per day). A cleavage of cyclic polyester oligomers under human intestinal conditions, which was assessed to be likely by the provided in vitro experiments, could consequently affect the risk assessment on polyester oligomers.
Thermal papers (e.g. point of sale receipts, adhesive labels, tickets) significantly contribute to contamination of paper material cycles and the environment with substances of (eco-) toxicological concern. In particular, they contain color developers like endocrine disrupting bisphenols in typical concentrations of about 1–2 percent per weight (wt%). Bisphenol A (BPA) was used as the common color developer over the last decades, but it will be restricted for thermal paper application in the European Union to a limit of 0.02 wt% from 2020 onwards. Consequently, a variety of BPA substituents such as bisphenol S (BPS) and its derivatives gain importance in thermal paper application. In this study, a rapid, reliable and cost-effective method for identification and quantification of BPA, alternative color developers and related substances like sensitizers is presented based on HPLC separation coupled with diode array detection (DAD) and Corona charged aerosol detection (CAD). Quantification was performed with regard to the intended use of the substances in thermal papers. Besides traditional UV external calibration using reference standards, alternative quantification approaches, in particular UV chromophore concentration for BPS derivatives and CAD universal response technique for low-volatile color developers, were applied and compared in order to allow quantification without reference substances. A market analysis for intended used color developers and sensitizers was performed on thermal paper samples (n = 211) collected in Germany during 2018 and 2019. Pergafast 201 (in 41.7% of the samples) was the most common color developer with concentrations above 0.02 wt%, followed by BPA (36.0%), BPS (13.3%) and other BPS derivatives known as D8, D-90, BPS-MAE and TGSA, that are mainly present in adhesive labels. Sensitizers were determined in over 90% of the samples.
Coatings for cans or closures are essential to protect the metal from corrosion and the food from migration of hazardous metal ions. Since coatings are no inert materials, they can release substances of potential health concern into food. In the present study, a comprehensive analysis is presented for a complex two-layered polyester–phenol-coating commercially used for metal closures of complementary infant food in sterilised glass jars. Focussed on the identity and migration of cyclic polyester oligomers as a kind of predictable non-intentionally added substances, polyester resin raw materials (n = 3) as well as individual coating layers (n = 3) were characterised by several analytical strategies (size exclusion chromatography, high-performance liquid chromatography mass spectrometry, diode array detection, charged aerosol detection, monomer determination after alkaline hydrolysis, overall migrate). The main polyester monomers were terephthalic acid, isophthalic acid, trimellitic acid, ethylene glycol, diethylene glycol, neopentylglycol, 2-methyl-1,3-propanediol, 1,4-butanediol and tricyclodecanedimethanol. The coatings were extracted with solvents acetonitrile and ethanol (24 h, 60°C), food simulants 50% ethanol, 20% ethanol and water (1 h, 121°C) as well as homemade and commercial baby food (1 h, 121°C). The released total polyester content determined by alkaline hydrolysis ranged from 288 µg/dm² (water, 1 h, 121°C) to 6154 µg/dm² (acetonitrile, 24 h, 60°C). However, individual cyclic oligomers, mainly dimers, were released from the coating to up to about 140 µg/dm². Migration into infant food was best represented by the food simulants water (up to 1% fat) and 20% ethanol (up to 5% fat). Cyclic polyester oligomers are classified as Cramer III substances by the threshold of toxicological concern concept associated to an exposure threshold of 1.5 µg/kg body weight per day. Exposure to cyclic polyester oligomers might be a potential concern for highly exposed infants.
Die Polyarylsulfon-Kunststoffe Polyethersulfon (PES) und Polyphenylensulfon (PPSU) werden seit dem Verbot von Bisphenol A (BPA) haltigem Polycarbonat vermehrt für die Herstellung von Babyflaschen verwendet. PES und PPSU sind enorm widerstandsfähige Kunststoffe gegenüber chemischen (Säuren/Basen), mechanischen und thermischen Einflüssen. Formal sind beide Polymere aus den Bausteinen Bisphenol S (BPS) sowie 4,4'-Dihydroxybiphenyl (DHBP) aufgebaut, welche nach derzeitigem Kenntnisstand eine ähnliche endokrine Wirkung zeigen können, wie das in Verruf geratene BPA. Ziel der Untersuchungen war es, am Markt erhältliche PES und PPSU Kunststoffe zu charakterisieren. Der Fokus lag dabei auf der Bestimmung von Substanzen, besonders Monomeren und Oligomeren, die aufgrund ihrer geringen Molekülgröße (< 1000 Dalton) potentiell von der Babyflasche auf das Füllgut übergehen können.
Since polycarbonate basically consisting of bisphenol A (BPA) was banned for the production of baby bottles, the polyarylsulfone plastics polyethersulfone (PES) and polyphenylsulfone (PPSU) became promising alternatives. PES and PPSU are extremely resistant materials to chemical (acids/bases), mechanical and thermal treatments. PES and PPSU are formally composed of bisphenol S (BPS) as well as 4,4‘-dihydroxybiphenyl (DHBP). Based on their bisphenolic molecular structure, both substances might cause similar endocrine effects compared to the banned BPA. In our study, we analyzed commercially available PES and PPSU materials used for baby bottles. We focussed on the identification and quantification of polymer related substances, mainly monomer derivatives as well as oligomers with a molecular weight below 1.000 dalton, as potential migrants into baby food.
Der Charged-Aerosol-Detektor (CAD) stellt eine innovative Detektionsmöglichkeit von schwerflüchtigen Analyten in der Hochleistungsflüssigchromatographie (HPLC) dar. Es handelt sich um einen unspezifischen, massen-proportionalen Detektor, der in Analogie zum verwandten Evaporative-Light-Scattering-Detektor (ELSD) schwerflüchtige Substanzen, unabhängig von deren chemischen Strukturmerkmalen, detektieren kann, jedoch Vorteile in der Empfindlichkeit und in der Linearität der Detektion aufweisen soll. Auf dem Gebiet der Konformitätsprüfung von Lebensmittelkontaktmaterialien, besonders bei der Durchführung von substanzunspezifischen Analysen (Screenings), kann somit der CAD eine wertvolle Option darstellen.
Bei der Nutzung von z.B. Polyethylenterephthalat (PET) für Getränkeflaschen und Trays oder Polybutylenterephthalat (PBT) für Küchenartikel können Oligomere in Lebensmittel migrieren. Die Monomere dieser Polykondensationskunststoffe sind mit Migrationsgrenzwerten in der Kunststoff VO 10/2011 gelistet (TPA: 7,5 EG: 30 BD : 5 mg/kg Lebensmittel). Bisher ist nicht bekannt, ob die migrierenden Oligomere im menschlichen Gastro-Intestinaltrakt hydrolysiert werden können. Zur Risikobewertung solcher nicht absichtlich zugesetzten Substanzen (NIAS) wird das TTC-Konzept (threshold of toxicological concern) angewandt. Den zyklischen halbaromatischen Oligomeren dieser Kunststoffe wird dabei ein Grenzwert für die Exposition von 90 μg/Tag/Person (Cramer III) zugeordnet, den linearen Oligomeren dagegen 1800 μg/Tag/Person (Cramer I). Durch einen simulierten Dünndarmverdau sollte geprüft werden, ob zyklische Oligomere des PBT bzw. PET im menschlichen Gastro-Intestinaltrakt zunächst zu linearen Oligomeren oder weiter bis hin zu den Monomeren abgebaut werden können.
Haftetiketten werden häufig für die Kennzeichnung mittels Clingfolien frisch abgepackter Lebensmittel (LM) verwendet. Diese Etiketten basieren meist auf dem Thermodruck-Prinzip, wobei das Druckbild über eine hitzeinduzierte, chemische Reaktion zwischen einem Leukofarbstoff und einem Farbentwickler in der Thermoaktivschicht des Etikettes gebildet wird (Erklärung rechts). Als Farbentwickler werden meist Bisphenole, wie das endokrin wirksame Bisphenol A (BPA), verwendet. Aufgrund ihrer hohen Konzentration im Etikett und der nicht kovalenten Bindung in der Thermoaktivschicht ist eine Migration vom Etikett durch die Clingfolie auf das Lebensmittel nicht auszuschließen. Ziel der Studie war es, das Übergangspotential von gesundheitlich relevanten Sub-stanzen aus Haftetiketten auf LM zu untersuchen. Dazu wurden anhand von Handelsproben eine Marktanalyse der in Haftetiketten verwendeten Farbentwickler vorgenommen, die korrespondierenden Clingfolien charakterisiert und Migrationsexperimente auf reale LM (Käse, Wassermelone) durchgeführt.
Polyphenylsulfone (PPSU) is a new material for the production of baby bottles. PPSU is a polyether plastic formally composed of bisphenol S (BPS) and 4,4ʹ-dihydroxybiphenyl (DHBP), which both have slight endocrine activities in in-vitro-tests. So far, little is known about the presence and the release of potentially hazardous substances from PPSU baby bottles. In our present study, we present a three step approach for the analysis of PPSU starting with polymer characterization in terms of chemical structure, total oligomer content and hydrolytic stability. Second is the determination of extractables focussing on monomers, monomer derivatives, linear and cyclic oligomers below 1000 dalton (Da) and residual solvent. Third is a risk assessment on migration-related substances in accordance to EU plastics regulation No 10/2011 based on triplicate consecutive migration experiments using official milk simulant 50% ethanol. We analysed five types of PPSU baby bottles from different brands as well as corresponding raw materials from different manufacturers by various analytical techniques (HPLC-DAD/FLD/Corona/ESI-MS, HPLC-SEC, GC-MS, ¹H-NMR). We found significant variations of PPSU materials from different producers with regard to polymer and oligomer chain end groups (methoxylation, chlorination), while total oligomer content below 1000 Da was similar (mean about 0.48%). BPS was not detected above 0.3 mg/kg polymer in any PPSU sample. Residual DHBP content ranged between 1.7 and 15.5 mg/kg polymer. The most common oligomer in all PPSU samples was the cyclic tetramer (about 1200 mg/kg polymer), which is the only cyclic compound below 1000 Da. Residual solvent, sulfolane, was determined to a maximum of 1300 mg/kg polymer. In migration tests, we detected exceedances of neither specific migration limits (SML) for listed substances nor of thresholds of toxicological concern (TTC) for non-listed substances (monomer derivatives, oligomers). Based on our analytical results, no concerns exist regarding migration of polymer-related substances from PPSU baby bottles.
Bisphenol A (BPA) was commonly used as color developer for thermal paper such as cash register receipts, labels or tickets. Therefore, thermal paper was considered by the European Food Safety Authority (EFSA) as the main source of human exposure to BPA beside epoxy based food contact materials. In this study, a German market analysis on the use of BPA and alternative color developers in thermal paper receipts is provided for the years 2015, 2016 and 2017.114 (2015), 98 (2016) and 99 (2017) samples were randomly collected and analyzed by HPLC-DAD. In summary, BPA was still the most frequently found color developer (48.2% in 2015, 46.9% in 2016 and 52.5% in 2017). The most commonly used alternative was the phenol-free substance Pergafast® 201 (34.2%, 33.7%, 40.4%). The bisphenol analogs bisphenol S (BPS; 11.4%, 9.2%, 6.1%) and D8 (6.1%, 7.1%, 1.0%) were less common. Another phenol-free substituent, a urea urethane compound (UU), was also detected (3.1% in 2016). Concentrations of color developers in thermal paper ranged from 1.4 to 32.4 mg/g (median values between 2.5 and 15.9 mg/g). Concentrations of BPA were found to be highest followed by BPS, UU, Pergafast® 201 and D8. In addition, two pharmacologically active substances, dapsone (6.0 mg/g) and tolbutamide (5.5 mg/g), were detected in a non-marketed thermal paper, that was supposed to use ascorbic acid as initial color developer. Different release experiments of the detected color developers were performed. Sensitizers 1,2-diphenoxy-ethane, 1-phenylmethoxy-naphthalene and diphenylsulfone, used frequently in the thermal paper processes, were quantified.
Food contact materials (FCM) made of metal, such as tin cans or closures for baby food, are often lacquered with a coating to protect against corrosion and a possible transfer of undesirable metal ions into food. As an alternative formulation to the etablished but potentially hazardous epoxy-phenol-coating based on bisphenol A (BPA), polyester-phenol-coatings are widely used. However, these coatings can also release substances with unknown toxicological potential into food in direct contact. Especially oligomers formed by polyester monomers are in focus. In this study, an analytical concept for the identification and determination of polyester oligomers releaseable from a commercial coating, used in closures for baby food, into food and food simulants is presented.