Determination of bisphenol-type contaminants from food packaging materials in aqueous foods by solid-phase microextraction-high-performance liquid chromatography

Food and beverage can coatings: A review on chemical analysis, migration, and risk assessment

The internal surface of food and beverage cans is generally covered with polymeric coatings to preserve food and protect metal substrate from corrosion. Coating materials are complex formulations that contain different starting substances (e.g., monomers, prepolymers, additives, etc.) and in addition during the manufacture of the material several compounds can be formed (e.g., reaction products, degradation products, etc.). These substances have the potential to migrate into the food. Many of them have not been identified and only some have been toxicologically evaluated. This article aims to provide a comprehensive review on the analytical methods used for the identification of potential migrants in can coatings. The migration and exposure to chemicals migrating from can coatings are also reviewed and discussed so far, which is essential for risk assessment. Moreover, a brief section on the current status of the legislation on varnishes and coatings for food contact in Europe is also presented. Liquid chromatography coupled to diode array and fluorescence detectors and particularly to mass spectrometry and gas chromatography-tandem mass spectrometry seem to be the techniques of choice for the identification of potential migrants in can coatings. Some studies have reported migration levels of BPA (bisphenol A) and BADGE (bisphenol A diglycidyl ether) and derivatives exceeding the specific migration limits set in the European legislation. On the whole, low dietary exposure to migrants from can coatings has been reported. However, it is interesting to highlight that in these studies the combined exposure to multiple chemicals has not been considered.

Preparation of 2D Graphene/MXene nanocomposite for the electrochemical determination of hazardous bisphenol A in plastic products

Bisphenol A (BPA) is one of the major contaminants with significant health hazards, which could also affect the endocrine system or induce cancer. It is essential to develop a highly sensitive and selective BPA sensor for environmental and food safety. Herein, 2D hybrid graphene/Ti₃C₂T_x nanocomposite (Gr/MXene) was prepared via a top-down method and then used to fabricate an electrochemical BPA sensor. The X-ray diffraction spectrometer (XRD) and Raman spectroscopy analysis were carried out to verify the successful formation of Gr sheets with MXene. The high resolution scanning electron microscopy (HR-SEM) was revealed the formation of MXene, and Gr/MXene nanocomposite. Furthermore, the 2D hybrid Gr/MXene nanocomposite modified glassy carbon electrode (GCE) was prepared for BPA oxidation in 100 mM phosphate buffer solution (PBS). Under the optimized condition, the Gr/MXene/GCE was displayed a linear range of detection from 10 to 180 nM and 1 to 10 μM BPA with the detection limits of 4.08 nM and 0.35 μM by amperometry and differential pulse voltammetry (DPV), respectively. Moreover, the proposed Gr/MXene modified electrode exhibited excellent stability, selectivity, repeatability and reproducibility towards the BPA detection. As a proof of concept, Gr/MXene modified sensor was effectively used to detect BPA in modern plastic products with the recovery ranging from 99.2 to 104.5%.

Ethoxylated Butoxyethanol-BADGE Adducts-New Potential Migrants from Epoxy Resin Can Coating Material

The acetonitrile extracts of can-coating materials have been analyzed by using high-pressure liquid chromatography/electrospray ionization-mass spectrometry (HPLC/ESI-MS). On the basis of detected ions [M + H]⁺, [M + NH₄]⁺, [M + Na]⁺ and product ions, the ethoxylated butoxyethanol-bisphenol A diglycidyl ether adducts were identified in two of the analyzed extracts. Although the oxyethylene unit-containing compounds are widely used for the production of different kinds of materials, the ethoxylated species have not been earlier detected in epoxy resin can-coatings.

Sensitive and selective electrochemical detection of bisphenol A based on SBA-15 like Cu-PMO modified glassy carbon electrode

This work reports the electrochemical detection of bisphenol A (BPA) using a novel and sensitive electrochemical sensor based on the Cu functionalized SBA-15 like periodic mesoporous organosilica-ionic liquid composite modified glassy carbon electrode (Cu@TU-PMO/IL/GCE). The structural morphology of Cu@TU-PMO is characterized by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Field emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET). The catalytic activity of the modified electrode toward oxidation of BPA was interrogated with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (pH 7.0) using the fabricated sensor. The electrochemical detection of the analyte was carried out at a neutral pH and the scan rate studies revealed that the sensor was stable. Under the optimal conditions, a linear range from 5.0 nM to 2.0 µM and 4.0 to 500 µM for detecting BPA was observed with a detection limit of 1.5 nM (S/N = 3). The sensor was applied to detect BPA in tap and seawater samples, and the accuracy of the results was validated by high-performance liquid chromatography (HPLC). The proposed method provides a powerful tool for the rapid and sensitive detection of BPA in environmental samples.

HPLC with Fluorescence Detection for Determination of Bisphenol A in Canned Vegetables: Optimization, Validation and Application to Samples from Portuguese and Spanish Markets

Bisphenol A (BPA) is one of the chemicals used to produce both polycarbonate plastics and epoxy resin coatings. Research has shown that small amounts of BPA can migrate into the foods and beverages enclosed in these types of containers. In this research, an analytical method based on high-performance liquid chromatography with fluorescence detection (HPLC-FLD) was developed and validated for the determination of BPA in canned vegetables. The results were confirmed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was performed, to identify the coating material of each tin can. Nineteen cans of vegetables were taken as study samples (eleven samples from the Spanish market, and eight samples from the Portuguese market). Excellent linear correlation (r2 = 0.9999) was observed over the range of 0.01 to 0.25 mg/L. Limit of detection (LOD) and limit of quantification (LOQ) values were calculated to be 0.005 mg/kg and 0.01 mg/kg, respectively. Good recoveries, between 72% and 90% were obtained at three different levels of concentration (RSD% = 4.6). BPA was not detected in the samples. The proposed HPLC-FLD was found to be suitable for the determination of BPA in canned vegetables.

Ultrasound assisted solvent extraction of porous membrane-packed samples followed by liquid chromatography-tandem mass spectrometry for determination of BADGE, BFDGE and their derivatives in packed vegetables

The problem of the presence of trace organic pollutants in food is of growing importance due to increasing awareness about their impact on newborns, infants and adults of reproductive age. Despite the fact that packaged food products offer many advantages, packaging can be a source of contamination for stored food. Thus, monitoring such pollution in food is of high importance. In this work, a novel methodology based on the solvent extraction of porous membrane-packed samples followed by liquid chromatography-tandem mass spectrometry was applied for the determination of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives in packed vegetables. Several parameters of the extraction process were optimized, including the volume and type of extraction solvent as well as the sonication time. Due to advantages such as simplicity of use, short analysis time, and a reduction in the required amount solvent, the developed procedure can be considered green. In addition, the developed methodology was characterized by good validation parameters. Limit if quantitation (LOQ) was found to be in the range of 0.8 to 1.5 ng/g. The obtained recoveries varied from 78.3% to 111.2%. The repeatability of the extraction ranged between 0.6% and 5.8% (RSD). The proposed method was successfully applied to determine the presence of BADGE, BFDGE and their derivative compounds in the vegetable samples stored in different types of containers. The obtained data indicate that the majority of investigated samples were contaminated by chlorinated and hydroxyl derivatives of BADGE.

Analysis of Selected Endocrine Disrupters Fraction Including Bisphenols Extracted from Daily Products, Food Packaging and Treated Wastewater Using Optimized Solid-Phase Extraction and Temperature-Dependent Inclusion Chromatography

The aim of this research is to demonstrate the concept and ability for the fast and preliminary screening of complex food and environmental samples for the presence of endocrine disrupters fractions, consisting of low-molecular mass micropollutants, particularly various bisphenols (A, B, C, E, F, S, Z, AF, AP, BP and FL). The developed analytical protocol for this research requires two main steps: (i) optimized solid phase extraction (SPE) for selective isolation, purification and pre-concentration of target fraction, and (ii) selective temperature-dependent inclusion chromatography for samples analysis via a HPLC-UV-VisDAD system using isocratic elution and internal standard quantification approach. The chromatographic experiment revealed that both β-CD and its hydroxypropyl derivative strongly interact with selected bisphenols. This is in contrast to the steroids and PAHs molecules investigated previously, where a strong interaction with β-cyclodextrin was observed. Integrated areas derived from acquired chromatographic profiles for each individual sample were used as the simple classification variable enabling samples comparison. We demonstrated that the proposed analytical protocol allows for fast estimation of EDC fractions in various daily use products, food and environmental samples. The materials of interest were selected due to the presence in surface water ecosystems of their residues, and finally, in raw wastewater including rice bags, plastic bags, cloths, sanitary towels, fish baits and various plastic foils from food products. Treated sewage water released directly to the environment from a municipal treatment plant (Jamno, Koszalin) was also investigated. It has been demonstrated that a whole range of low-molecular mass compounds, which may be detected using UV-Vis detector, can easily be emitted from various in daily use products. The presence of micropollutants in treated wastewater, water ecosystems and plastic waste utilization via technological wastewater treatment processes must be addressed, especially in terms of microplastic-based pollutants acting as endocrine disrupters. It is hoped that the proposed simple analytical protocol will be useful for fast sample classification or selection prior to advanced targeted analysis involving the more accurate quantification of specific analytes using e.g., mass spectrometry detectors.

The occurrence of bisphenol plasticizers in paired dust and urine samples and its association with oxidative stress

Bisphenol A diglycidy ether (BADGE) and its derivatives are epoxy resins and widely used as emerging plasticizers in food packages and material coating. Though known as endocrine disruptors, little information is available on their occurrence, exposure routes and toxicity. Besides, the analysis of BADGE and its derivatives has always been a challenge due to their reactive chemical properties and the background contamination. Therefore, we firstly developed a novel water-free method to analyze BADGE and its derivatives in dust samples together with other two typical plasticizers bisphenol A (BPA) and bisphenol S (BPS). In order to investigate the levels in paired dust and urine samples, 33 paired samples were collected from Singapore. In both dust and urine samples, the predominant compounds were BPA, BADGE-2H₂O and BPS. A significantly positive correlation of BPA levels in paired dust and urine samples was observed in this small-scale study. To tentatively explore the human health effect from exposure to these bisphenol plasticizers, we assessed the correlation between the urinary concentrations of these compounds and oxo-2'-deoxyguanosine (8-OHdG), an oxidative stress biomarker. The result showed that 8-OHdG levels in urine samples was positively correlated with urinary BPA level and body mass index (BMI), suggesting that elevated oxidative stress might be associated with BPA exposure and obesity. In the future, a larger scale study is warranted due to the limited sample size in this study.

Determination of bisphenol A in red wine using a double vortex-ultrasound-assisted microextraction assay: Role of the interfacial properties

Bisphenol A (BPA) is a synthetic compound broadly used in medical devices as well as in packaging of food and drinks. Recently, BPA toxicity has become of concern to environmental public health. Red wine that is susceptible to BPA contamination is an alcoholic beverage made from yeast fermentation of grapes in the presence of grape skins so as to extract phenolic compounds. The aim of this study was to validate an efficient, low cost, and time-saving method for BPA determination in red-wine beverage. To this end, a rapid and simple microextraction method is here proposed consisting in liquid-liquid separation assisted by a vortex-ultrasound-vortex procedure combined with gas chromatographic analysis (GC-Fid or GC-IT/MS). By means of a comparative study between real red-wine matrix and synthetic hydroalcoholic solutions, different parameters related to the microextraction steps were investigated. The minimal amount of extraction solvent for a given volume of sample was calculated for both the systems. It was demonstrated that for red-wine matrix, the extent of phase separation is strongly affected by some wine constituents and that separation can be tuned by varying the amount of the extraction solvent. This double vortex-ultrasound-assisted method achieved high recovery of BPA and enrichment factor compared with other microextraction methods.

Determination of Nine Bisphenol-Diglycidyl Ethers in Human Breast Milk by Ultrahigh-Performance Liquid Chromatography Tandem Mass Spectrometry

Because of their widespread use, and the mutagenicity and teratogenicity observed in in vitro studies, bisphenol-diglycidyl ethers (BDGEs) were suspected of posing health risks to humans, especially to infants. Quantifying exposure of BDGEs from breast milk is essential in assessing the potential health risks of these ubiquitous compounds to infants. However, there is no reported analytical method for the determination of BDGEs in breast milk. In this context, we developed a rapid and sensitive method based on ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to measure nine BDGEs in breast milk. The analytes were extracted with acetonitrile and fat was removed by freezing under -20 °C. The extracts were further purified by PRiME HLB solid-phase extraction (SPE) cartridge. The limits of detection (LODs) and quantification (LOQs) for the analytes were 0.033-0.500 and 0.100-1.500 μg L^-1, respectively. The recoveries of BDGEs were ranged from 71.33% to 114.33%. Good method reproducibility regarding intra- and interday precision was observed, yielding relative standard deviations (RSDs) less than 11.81% and 10.83%, respectively. The proposed method was successfully applied to 20 breast milk samples. BADGE·2H₂O, BADGE·HCl·H₂O, BADGE·H₂O, BADGE·HCl, BFDGE·2H₂O, and BFDGE·2HCl were detected. BFDGE·2HCl was the dominant BDGE with detection rate of 65.0% and the concentration ranging from 0.4 to 1.0 μg L^-1. This is the first report describing the occurrence of BDGEs in breast milk.

Spectroscopic and molecular modeling approaches to investigate the interaction of bisphenol A, bisphenol F and their diglycidyl ethers with PPARα

A fluorescence polarization (FP) assay for the simultaneous determination of bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE) was developed. The method was based on the competition between bisphenols (BPs) and fluorescein-labeled dexamethasone derivative (Dex-fl) for mouse peroxisome proliferator-activated receptor α ligand binding domain (mPPARα-LBD). A recombinant soluble protein derivative mPPARα-LBD* was prepared, then in vitro binding of 4 BPs to mPPARα-LBD* was investigated. Fluorescence polarization assay showed that these compounds exhibited different binding potencies with mPPARα-LBD*. Additionally, molecular dynamics simulations were performed to further understand the mechanism of BPs binding affinity for mPPARα-LBD*. Docking results elucidated that the driving forces for the binding of BPs to mPPARα-LBD* were predominantly dependent on hydrophobic and hydrogen-bonding interactions. Comparison of the calculated binding energies vs. experimental binding affinities yielded a good correlation (R² = 0.7258). The proposed method has potential for multi-residue detection of BPA, BPF, BADGE, and BFDGE.

A high-throughput screening method of bisphenols, bisphenols digycidyl ethers and their derivatives in dairy products by ultra-high performance liquid chromatography-tandem mass spectrometry

A simple and universal analytical method based on ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for high throughput screening of 21 bisphenols, bisphenols digycidyl ethers and their derivatives in dairy products was developed. Response Surface Methodology (RSM) was used to optimize sample preparation conditions based on a quick, easy, cheap, effective, rugged and safe (QuEChERS) method. The analytes were extracted by using 15 mL acetonitrile with 1% acetic acid, and the extracts were further purified by using 190 mg of C18 and 390 mg of PSA. The extracts were analyzed by UHPLC-MS/MS with electrospray ionization (ESI) source. Linearity was assessed by using matrix-matched standard calibration and good correlation coefficients (r² > 0.99) were obtained. The limits of quantitation (LOQs) for the analytes ranged from 0.02 to 5 μg kg^-1. The extraction recoveries were in a range of 88.2%-108.2%. Good method reproducibility in terms of intra- and inter-day precision was observed, yielding relative standard deviations (RSDs) less than 8.9% and 9.9%, respectively. The validation method results revealed that the proposed method was sensitive and reliable. Finally, this method was successfully applied to dairy product analysis.

Automated solid-phase extraction of organic pollutants using melamine–formaldehyde polymer-derived carbon foams

Solid-phase extraction of environmental pollutants is accomplished using carbon foams derived from melamine–formaldehyde polymer foams.

Determination of bisphenol-type endocrine disrupting compounds in food-contact recycled-paper materials by focused ultrasonic solid-liquid extraction and ultra performance liquid chromatography-high resolution mass spectrometry

Focused ultrasonic solid-liquid extraction (FUSLE) and reverse-phase ultra performance liquid chromatography (UPLC) coupled to a quadrupole-time of flight mass spectrometer (Q-TOF-MS) was applied to the determination of bisphenol-type endocrine disrupting compounds (EDCs) in food-contact recycled-paper materials. Recycled paper is a potential source of EDCs. Bisphenol A (BPA), bisphenol F (BPF) and their derivatives bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE) are used for the production of epoxy resins employed in the formulation of printing inks. The FUSLE of bisphenol-type EDCs from packaging is reported for the first time. First, different extraction solvents were studied and methanol was selected. Then, the main FUSLE factors affecting the extraction efficiency (solvent volume, extraction time and ultrasonic irradiation power) were studied by means of a central composite design. The FUSLE conditions selected for further experiments were 20 ml of methanol at ultrasonic amplitude of 100% for 5s. Finally, the number of extraction cycles necessary for complete extraction was established in two. The analysis of the FUSLE extracts was carried out by UPLC-Q-TOF-MS with electrospray ionization and the determination of the four analytes took place in only 4 min. The FUSLE and UPLC-ESI-QTOF-MS method was validated and applied to the analysis of different food-contact recycled-paper-based materials and packaging. The proposed method provided recoveries from 72% to 97%, repeatability and intermediate precision under 9% and 14%, respectively, and detection limits of 0.33, 0.16, 0.65 and 0.40 μg/g for BPA, BPF, BADGE and BFDGE, respectively. The analysis of paper and cardboard samples confirmed the presence of EDCs in these packaging.

Bis(hydroxyphenyl)methane-bisphenol F-metabolism by the HepG2 human hepatoma cell line and cryopreserved human hepatocytes

Bisphenol F (BPF) is present in the environment and as a contaminant of food. Humans may, therefore, be exposed to BPF, and an assessment of this risk is required. BPF has been shown to have genotoxic and endocrine-disruptor properties in a human hepatoma cell line (HepG2), which is a model system for studies of xenobiotic toxicity. In this study, we investigated the ability of HepG2 cells to biotransform BPF, because metabolism may affect the observed effects of BPF, and we compared this metabolic capacity with that of human hepatocytes. Cells were incubated for 24 hours with [(3)H]-BPF. The culture medium was then concentrated and its metabolites were isolated by high-performance liquid chromatography and identified by mass spectrometry. BPF was largely metabolized into the corresponding sulfate by the HepG2 cell line. BPF was metabolized into both sulfate and glucuronide by human hepatocytes, but with differences between individuals. The metabolism of BPF in both HepG2 cells and human hepatocytes suggests the existence of a detoxification pathway. Thus, these two cell models differ in metabolic capacity. It is, therefore, very important, when assessing the toxic effects of substances in vitro, to determine, in parallel, the biotransformation capacities of the model used to extrapolate in vivo.

Fast liquid chromatography-tandem mass spectrometry for the analysis of bisphenol A-diglycidyl ether, bisphenol F-diglycidyl ether and their derivatives in canned food and beverages

In this work a fast liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method using a C18 Fused Core™ column, was developed for the simultaneous analysis of bisphenol A diglycidyl ether (BADGE), bisphenol A (2,3-dihydroxypropyl) glycidyl ether (BADGE·H(2)O), bisphenol A bis(2,3-dihydroxypropyl) ether (BADGE·2H(2)O), bisphenol A (3-chloro-2-hydroxypropyl) glycidyl ether (BADGE·HCl), bisphenol A bis(3-chloro-2-hydroxypropyl) ether (BADGE·2HCl) and bisphenol A (3-chloro-2-hydroxypropyl)(2,3-dihydroxypropyl ether) (BADGE·HCl·H(2)O) and bisphenol F diglycidyl ether (BFDGE), bisphenol F bis(2,3-dihydroxypropyl) ether (BFDGE·2H(2)O), bisphenol F bis(3-chloro-2-hydroxypropyl) ether (BFDGE·2HCl). The LC method was coupled with a triple quadrupole mass spectrometer, using an ESI source in positive mode and using the [M+NH(4)](+) adduct as precursor ion for tandem mass spectrometry experiments. The method developed was applied to the determination of these compounds in canned soft drinks and canned food. OASIS HLB solid phase extraction (SPE) cartridges were used for the analysis of soft drinks, while solid canned food was extracted with ethyl acetate. Method limits of quantitation ranged from 0.13 μgL(-1) to 1.6 μgL(-1) in soft drinks and 1.0 μgkg(-1) to 4.0 μgkg(-1) in food samples. BADGE·2H(2)O was detected in all the analyzed samples, while other BADGEs such as BADGE·H(2)O, BADGE·HCl·H(2)O, BADGE·HCl and BADGE·2HCl were also detected in canned foods.

Multiple-stage mass spectrometry analysis of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether and their derivatives

The fragmentation of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives was studied by electrospray ionization tandem mass spectrometry. Multiple-stage mass spectrometry and accurate mass measurements were combined to establish the fragmentation pathways. BADGEs and BFDGEs tend to form ammonium adducts under electrospray conditions which fragmented easily. The fragmentation of [M+NH(4)](+) for BADGEs started with the cleavage of the phenyl-alkyl bond, which was followed by the α-cleavage of the ether group to generate the characteristic product ions at m/z 135, [C(9)H(11)O](+), and m/z 107, [C(7)H(7)O](+). The fragmentation of the BFDGE isomer mixtures was studied by on-line reversed-phase liquid chromatography coupled to multiple-stage mass spectrometry (LC/MS(n)). Information obtained from product ion spectra for each BFDGE isomer and its comparison with the fragmentation pathway of BADGE allowed each isomer and the chromatographic elution order to be identified.

Determination of endocrine disruptors in honey by CZE-MS using restricted access materials for matrix cleanup

An analytical method based on CZE coupled to ESI-MS is proposed for the identification and simultaneous quantification of several endocrine-disrupting chemicals in honey. The target compounds were the chlorophenols: 2,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol, and bisphenol-A, 4-tert-butylphenol, and 4-tert-butylbenzoic acid. A two-step optimization of the ESI-MS detection was carried out. First, the organic solvent present in the sheath liquid was selected and its effect on the analytical signal was studied. The best results in terms of the intensity of the MS signals were obtained with methanol. Thus, an experimental design technique (Doehlert type) was used for the optimization of the other parameters: the NH(3) concentration in the sheath liquid, the flow of the sheath liquid, the nebulizer pressure in ESI, and the drying gas temperature and flow. Here, we developed a new sample treatment based on the combined use of a restricted access material and a polymeric sorbent for SPE. The LOD achieved were in the range of 5-31 ng/g. The intraday precision of the proposed method was determined from replicate analyses (n=4) at a concentration level of 50 ng/g, with RSD values in the range of 15-23%. The results revealed that the proposed method is suitable for the reliable quantification of endocrine-disrupting chemicals in honey at nanograms per gram levels.

Study on the migration of bisphenol-A from baby bottles by stir bar sorptive extraction-thermal desorption-capillary GC-MS

Migration of bisphenol-A (BPA), the principal monomer of polycarbonate (PC) baby bottles, was investigated using an aqueous migration simulant. BPA was determined in 200 mL water samples using stir bar sorptive extraction (SBSE) after in situ derivatization with acetic acid anhydride followed by thermal desorption (TD)-capillary GC-MS. The concentration of BPA was calculated using the deuterated internal standard d6-BPA. Calibration for BPA was shown to be linear in a concentration range from 1 ng/L to 10 microg/L with a correlation coefficient >0.99. The LOD for BPA (as acetate) was 0.12 ng/L and LOQ 0.40 ng/L (ppt). PC bottles were heated in a water bath and in a microwave oven at four different temperatures (37, 53, 65, and 85 degrees C). The higher the temperature, the more the BPA was released, and after a few heating cycles, the released concentrations became constant. At normal use, i.e. at 37 degrees C, concentrations are ca. 10 ng/L. No significant difference was noted between water bath and microwave heating illustrating that migration of BPA is mainly temperature dependent.