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Evaluation of long term migration testing from cans coatings into food simulants: Epoxy and acrylic–phenolic coatings. Rafael Paseiro-Cerrato, Jonathan W. DeVries, and Timothy H. Begley J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b00081 • Publication Date (Web): 10 Mar 2017 Downloaded from http://pubs.acs.org on March 14, 2017
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Journal of Agricultural and Food Chemistry
TITLE Evaluation of short and long term migration testing from cans coatings into food simulants: Epoxy and acrylic–phenolic coatings. AUTHORS R. Paseiro-Cerrato1*, J. DeVries2 T. H. Begley1 1
US FDA, Center for Food Safety and Applied Nutrition, 5001 Campus Drive, College Park, MD, 20740, USA 2 DeVries & Associates, 2261 105th Lane NW, Coon Rapids, MN 55433-4157, USA
*Corresponding Author Rafael Paseiro-Cerrato US FDA, 5001 Campus Drive, College Park, MD, 20740, USA Phone number: 1-240-402-1370 Fax number: 1-301-436-2634 Email:
[email protected] 1 ACS Paragon Plus Environment
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ABSTRACT
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Traditionally, migration testing during 10 days at 40 °C has been considered sufficient and
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appropriate for simulating the potential migration of substances from food contact materials into
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foods. However, some packages, such as food cans, may be stored holding food for extended
5
time periods (years). This study attempts to verify whether common testing conditions accurately
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estimate long term migration. Two types of can coatings, epoxy and acrylic-phenolic, were
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subjected to short and long term migration testing (1 day to 1.5 years) using food simulants
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(water, 3% acetic acid, 50% ethanol and isooctane) at 40 °C. Using HPLC-DAD/CAD, HPLC-
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MS, UHPLC-HRMS (where HRMS is accurate mass, mass spectrometry) and DART-HRMS we
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identified potential migrants before starting the experiment: BPA, BADGE, BADGE derivatives,
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benzoguanamine, and other relevant marker compounds. During the experiment using a water-
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based food simulant, migrants remained stable. Most of the cans in contact with 3% acetic acid
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did not survive the experimental conditions. Tracked migrants were not detected in isooctane. In
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the presence of 50% ethanol, the traditional migration test during 10 days at 40 °C did not
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predict migration during long term storage. These results suggest that migration protocols should
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be modified to account for long term storage.
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KEYWORDS: Food packaging, can coatings, epoxy-resin, acrylic-phenolic, long term migration, direct
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analysis in real time (DART), LC-DAD/CAD, LC-MS, UHPLC-HRMS, NIAS.
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INTRODUCTION
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Bisphenol A (BPA) has been commonly used monomer for polymers used in food contact
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material (FCM) applications. Examples of FCMs containing BPA include polycarbonate and
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epoxy-based can coatings 1, 2. For many years, BPA has received attention due to suspected
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toxicological effects. However, BPA migration from packaging into food occurs at very low
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concentrations3, 4 and is not expected to be a risk for consumers 5. In addition, several regulatory
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agencies agree that BPA poses no health risk for consumers of any age at the dietary exposure
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concentrations consumed6, 7. Due to various perceptions surrounding BPA, new formulations of
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can coatings, such as polyester, acrylic-phenolic, and PVC, have been introduced in the market
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as potential replacements for epoxy-based materials.
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Polymers, such as coatings, are manufactured using monomers and additives. The resulting final
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materials may have unreacted substances that can potentially migrate into the food. Several
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studies dealt with the measurement of unreacted stating substances from epoxy-resins8-11. In
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addition, non-intentionally added substances also known as NIAS (e.g. oligomers, products of
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degradation) may also occur. These compounds are formed because of chemical side reaction
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during the manufactured process. NIAS could also potentially migrate from the FCM into the
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food. Due to the unknown nature of most NIAS, most of them are not toxicologically evaluated.
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Identifications of some of these substances were performed in several types can coatings as well
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as analysis into food or food simulants12-19.
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Based on FDA Guidance documents 20, migration tests performed at 40 °C for 10 days, are often
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considered appropriate for simulating the migration of substances into food. For high
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temperature, heat sterilized, or retorted products, a thermal treatment at 121 °C for two hours
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continued by the conventional migration test is also recommended. Migration testing typically
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uses food simulants (e.g. water, 3% acetic acid) instead of actual food to simplify analysis.
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However, because cans containing food may be stored for years, rather than months, those
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migration protocols might not accurately simulate the likelihood of migration or reaction
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products (hydrolysis) over extended time periods. The goal of this investigation was to evaluate
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whether the accepted “short term” migration protocols accurately predict migration during long
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term storage conditions.
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We performed long term migration testing in polyester can coatings 12 and in PVC-coated cans
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21
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cans, to assess the long term migration patterns of two other types of coatings, epoxy-resins and
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acrylic phenolic coatings. Our results provide valuable data for understanding migration patterns
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over extended time periods.
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MATERIALS AND METHODS
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Chemicals and standards solutions
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Acetonitrile (ACN) (Optima® for LC-MS), methanol (Optima® for LC-MS), isooctane
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(Optima®) and water (Optima® for LC-MS) were obtained from Fisher Scientific (Fair Lawn,
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New Jersey). Tetrahydrofuran (THF) for HPLC and ethyl alcohol absolute were from Acros
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(New Jersey, USA). 2,4-Diamino-6-phenyl-1,3,5-triazine (benzoguanamine, (BGA)) 97%,
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Bisphenol A ≥ 99% and Bisphenol A –d16 98 atom % D (BPA-d16) were from Aldrich (St.
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Louis, MO, USA). Bisphenol A diglycidyl ether ≥ 95% (BADGE), Bisphenol A(3-chloro-2-
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hydroxypropyl) glycidyl ether ≥ 90% (BADGE.HCl), Bisphenol A(2,3- dihydroxypropyl)
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glycidyl ether ≥ 95% (BADGE.H2O), Bisphenol A bis (3-chloro-2-hydroxypropyl) ether ≥ 97%
. In this study, we have used a protocol similar to that used for evaluating polyester coated
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(BADGE.2HCl), Bisphenol A bis (2,3- dihydroxypropyl) ether ≥ 97% (BADGE.2 H2O) and
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formic acid for LC-MS ˜ 98% were from Fluka (St. Louis, MO, USA). Bisphenol A (propane –
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D6, 98%) (BPA-d6) were purchased to Cambridge Isotope Laboratory Inc. (Andover, MA,
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USA). Distilled white vinegar (5% acidity) was provided by an industrial partner and diluted
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with water to reach 3% acetic acid solution.
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Instrumentation
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A protocol similar to Paseiro-Cerrato’s method for identifying polyesters 13 was used to identify
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substances migrating from the coatings (“migrants”). Briefly, FTIR using a diamond-ATR
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sample cell was used to identify coating materials, and HPLC-DAD/MS, HPLC-DAD/CAD,
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UHPLC-HRMS and DART-HRMS were used to identify non-volatile compounds initially
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present in the coating. The instrument settings and detailed protocol for identifying migrants
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were described in previous publication.
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During the migration experiments, HPLC coupled to a Diode Array Detector (DAD) and to a
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Charge Aerosol Detector (CAD) as well as a HPLC coupled to a Mass Spectrometer (MS) were
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used to detect Bisphenol A diglycidyl ether (BADGE), BADGE derivatives, and potential
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unreacted oligomers that could migrate into the different food simulants. Instrument settings
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were as described in Paseiro-Cerrato11 with slight modification. For the epoxy-resins analysis,
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the HPLC-MS was used only in the positive mode. For acrylic-phenolic coatings analysis by
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DAD, wavelengths 220, 230 and 266 were used, rather than the 225, 242 and 288 nm settings.
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Due to the lack of commercially available standards for BADGE derivatives and unknown
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migrants, BADGE.2H2O was used for quantification of these migrants in the long term
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migration. For BADGE determination, standards of BADGE, BADGE.H2O, and BADGE.2H2O
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were employed. For BGA determination in acrylic-phenolic cans, the same method, using
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UHPLC-HRMS as described by Vaclavikova21 was used.
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We used an UFLC XR ( Shimadzu, Kyoto, Japan) coupled to a 4000 Qtrap, controlled by
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Analyst, Version 1.6.2 software (Applied Biosystems, Foster City, CA, USA) for BPA
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determination. The column was an Agilent Polaris 3 C18 (150 x 2.0 mm) thermostatted at 35 °C.
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The autosampler was maintained at 15 °C, the flow rate was 0.1 mL/min, and the injection
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volume was 5 µL. The mobile phases were water (A) and acetonitrile (B). The gradient, starting
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at 60% of A, was maintained for 2 min, then decreased to 0% in 8 min., at which point it was
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held for 5 min. Afterwards, the mobile phase was returned to the starting ratios and held for 5
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min. The total run time was 20 min. The MS data were acquired in MRM using an electrospray
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source (ESI) in the negative mode and the detector was set as follows: ion source gas one was
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60, ion source gas two was 90, curtain gas 30, ion spay voltage - 4500, temperature 450 °C; the
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declustering potential was -55, and entrance potential was -10. The MS/MS transitions were: For
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BPA, 227.3 m/z to 212.3 and 133.1, collision energy (CE) was -28 and -36 respectively. For the
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internal standard BPA-d16, m/z 241.0 to 222.3 (CE = -29) and 142.2 (CE = -36).
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Migration experiment and coating extraction
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The cans used in this study (calculated area= 4.57 dm2 and calculated volume = 740 mL) were
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provided by an industrial partner. For the coating extraction assays, epoxy-resins and acrylic
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phenolic cans were extracted three times with acetonitrile (ACN) at 40 °C for 24 hours.
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Acetonitrile extracts were used for identification of potential migrants as well as for total extract
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of migrants from the coatings.
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Filling and sealing of the acrylic and epoxy-coated cans were performed by an industrial partner,
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using water and 3% acetic acid as food simulants, which had been previously heated to 38 °C.
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From among these cans, a half was placed at room temperature for cooling (non-retorted). The
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rest of the cans were heated to 127 °C for 24 minutes (retorted), as is common in industrial
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practice, before being allowed to cool to room temperature. Additional acrylic and epoxy-coated
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cans were filled and sealed in the laboratory with either 50% ethanol or isooctane. The ethanol
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solution was sonicated for 15 minutes and sparged with nitrogen for 5 minutes prior to being
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used for can filling.
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Cans were placed into the oven at 40 °C for 1, 10, 30, 90 and 180 days, 1 and 1.5 years. The one
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year migration period for epoxy cans was equivalent to 305 days; the 1.5 years migration period
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was equivalent to 475 days for acrylic-phenolic and 490 days for epoxy-resins. A migration
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period of 30 days was used for epoxy-resins cans and 180 days for acrylic-phenolic food cans.
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Migration times for 1 day, 10 days, 1 year, and 1.5 years were performed in triplicate for epoxy
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resins and migration times at 10 days, 180 days, and 1.5 years were conducted in triplicate for
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acrylic phenolic cans. Control samples of simulants and a zero time point for retorted cans were
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also analysed. After each migration period, samples were analysed on the same day the cans
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were opened or the simulant was transferred into glass vials with polypropylene lids and PTFE
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septa, and then stored in the refrigerator (2-8 °C) until analysis. An extra migration experiment at
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40 °C, using 50% ethanol for 1, 10, 30 and 130 days, was conducted using two different epoxy
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cans, one with a white coating and the other with yellow-coloured coating.
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Method development
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Twenty-five millilitres of water and 3% acetic acid food simulant samples were poured in an
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Agilent Bond Elut C18, 500 mg 3mL column, which had been conditioned using 3 mL of
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methanol followed by 3mL of the corresponding simulant. Compounds were eluted using 1 and 2
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mL of ACN for the acrylic and epoxy coatings, respectively. For 50% ethanol and isooctane, 25
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mL of migration simulant were concentrated (Rapidvap®, Labconco corporation, Kansas City,
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MO), almost to dryness, then 5 mL ACN were added to the concentrates. At that point the ACN
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of the samples was re-concentrated to 1 mL, under a N2 stream at 40 °C using a Techne DB-3A
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sample concentrator. All concentration steps were carried out in glass equipment. Prior to the
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concentration step, all food simulants were spiked with 5 µL of an ACN solution of BPA-d6 (400
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µL/mL), except for the isooctane food simulant, which was spiked with a BPA-d6 solution in
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THF; this compound serving as a surrogate standard. Samples were then filtered using a 0.2 µm
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PTFE membrane filter. In addition, to perform the analysis by HPLC-DAD/CAD, 0.2 mL of
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concentrated ACN from simulants water and 3% acetic acid were diluted to 1mL with water. For
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BADGE and BADGE derivatives determination, samples were injected by LC-MS. The same
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systems were used to analyse concentrated ACN samples for the identification as well as the
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pure simulant of water retorted cans and 50% ethanol. ACN can extracts used for identification
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were concentrated from 25 to 1 mL under N2 stream at 40 °C. For BPA determination, 0.4 mL of
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ACN, spiked with a BPA-d16 acetonitrile solution (used as an internal standard) was analysed by
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LC-MS/MS.
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Recovery was evaluated using the following compounds: BPA, BADGE, BADGE.H2O,
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BADGE.2H2O, BADGE.HCl, BADGE.2HCl and BPA-d6. The spiking level for BPA was 0.4
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ng/mL and for the rest of compounds the spiking amounts ranged from 0.4 to 0.8 µg/mL. For
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BADGE assessment, a stability test was conducted from 1 day to 120 days in acetic acid, ethanol 8 ACS Paragon Plus Environment
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10%, water and isooctane conditions. For BPA, the stability test to 120 days was conducted in
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50% ethanol.
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RESULTS AND DISCUSSION
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Identification of migrants
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The exact can coating formulations and compositions for these studies were not available before
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testing. Therefore, the first step was to identify the compounds that could potentially migrate
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from these can coatings into the food simulants. We used a protocol similar to that described by
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Paseiro-Cerrato11 to identify the types of coating and the potential migrants. Because little
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difference was observed between the results obtained by DAD and CAD, only results obtained
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by DAD are displayed.
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FTIR
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Identification of the type of coating for the two types of cans in this study was performed using
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FTIR. Our data illustrates that the can bodies with epoxy-resin coating, were based on Bisphenol
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A and epichlorohydrin (72 %) (Figure 1). The can lids used in our study were either poly
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(trimethylene isophthalate) (66%) or epoxy resin ester Bisphenol A (61%). For to the acrylic
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phenolic cans, the best match of the can body IR spectra corresponds with a phenol resin (62%)
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and poly(dicyclononyl itaconate) 54 % or poly( 11-bromoundecyl methacrylate) 53% (Figure 1).
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The can top matched with 73 % of PETE (40%) + PBTE (60%). Results for the cans used in our
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additional migration experiments using 50% ethanol simulants, best fit the profiles of cured high
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strength epoxy (92%) for the white coating and extra time epoxy water resistant high strength
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(89%) for the yellow coloured coating.
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-
The use of HPLC coupled to DAD, CAD, MS and HRMS for migrant identification.
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Based on our laboratory experience and in previous studies13, 22, we selected acetonitrile (ACN)
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as the most appropriate solvent for extracting the unreacted compounds remaining in the coating.
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This solvent was in contact with the can coatings for 24 h at 40 °C. A concentration step was
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performed to reduce 25 to 1 mL, and the ACN was analysed by HPLC coupled to different
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detectors.
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The extracts from epoxy-resins, analysed using the DAD, presented several chromatographic
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peaks with spectra consistent with BADGE derivatives at 232 nm and 280 nm. However, spectra
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from other chromatographic peaks having maximum molar absorptions at 230, 262, and 340 nm
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were also obtained. A very similar spectra (maximum molar absorption 228, 266 and 346 nm)
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was identified in most of acrylic-phenolic migrants in the ACN extract. Interestingly, spectra
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with similar molar absorptions had been identified during our previous study of polyester can
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coatings 12. Because these types of compounds are more common in acrylic-phenolic coatings, it
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is quite possible that the compounds we have detected are derivatives of acrylic and/or phenolic
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compounds; nonetheless, we would need to have comparative analyses using standards of those
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types of compounds to confirm this hypothesis. On the other hand, we also found
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chromatographic peaks from the acrylic-phenolic cans with spectra at max 248, 282, and 332 as
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well as 242 and 288 nm, but the identity of these compounds could not be confirmed (Table 1).
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To analyse the extracts from epoxy-resin cans, we also ran the HRMS detector in positive and
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negative mode, from 100 to 1000 m/z and several chromatographic peaks with different m/z
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were obtained. These masses were compared to an in laboratory list, which had been developed
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based on the possible starting substances and BADGE derivatives already identified by Schaefer
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et al. 15 and Berger et al. 23. We also took into account possible products of hydrolysis with
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water and hydrochloric acid, the resulting adducts, including H+, ACN+, Na+, K+, and H-, and n
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repetitions of BADGE units up to 1000 m/z. The MS and database only included compounds up
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to 1000 m/z because is generally recognized that hydrocarbon compounds above this mass range
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are typically not absorbed through the intestinal tract and consequently these are generally
201
considered not a hazard for consumption. The accurate mass with good ppm mass agreement (≤
202
5 ppm) as well as the suggested molecular formula estimated by fitting with Xcalibur software
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TM
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Additionally, ACN were also injected by HPLC-DAD/MS and the proposed compounds were
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assigned to peaks obtained by DAD. Compounds had the appropriate spectra of BADGE
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derivatives as well as an appropriate retention times with regard to the molecular weight. The
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results obtained using these analytical techniques and the agreement with the published
208
literature15, 23 give confidence in the identification of the BADGE derivatives. Identified
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compounds in epoxy-resin are reported in Table 2.
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The extracts from cans lined with acrylic-phenolic resins were also injected and analyzed using
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HPLC-HRMS, but, due to the high number of potential acrylic monomers in this type of can and,
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to the best of our knowledge, the lack of published literature in this topic, identification of
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acrylic-phenolic derivatives was not achieved.
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Using TOX ID software version 2.1.2, data obtained by HRMS for both coatings were compared
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with an internal laboratory list of monomers and additives listed in the FDA Food Contact
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Notification System and substances included in EU positive list until 2013. Several compounds
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were identified by this process. These compounds were purchased and injected using the same
2.2 (Thermo Fisher Scientific, San Jose, CA, USA) gives confidence in the identification.
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chromatographic method in HRMS. BADGE was identified in both cans. In addition, BGA was
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identified in acrylic-phenolic cans.
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In summary, for epoxy phenolic cans, BPA, BADGE, BADGE 1st and 2nd product of hydrolysis,
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identified BADGE derivatives as well as unknowns 1 and 2 were monitored in this study. For
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cans having acrylic-phenolic coatings, BPA, BADGE, BADGE 1st and 2nd product of hydrolysis,
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and BGA were monitored during the migration experiment, as well as several unidentified
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migrants which gave high responses in the DAD detector (Table 1). In most samples, our
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BADGE determination was in the form BADGE.2H2O. We used BADGE.2H2O as a proxy to
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track the relative changes in intensity among BADGE derivatives and unknown migrants during
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the migration periods.
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Identification of BADGE derivatives and monomers by DART-HRMS
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DART-HRMS was used for direct screening of the oligomers in the epoxy coating. Data were
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compared with DART analysis of the ACN concentrated extract (25 mL to 1 mL) and the not
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concentrated ACN can extract. Table 2 presents the identified BADGE derivatives detected by
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DART. Most of these compounds were detected in the positive mode. Of the 10 identified
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substances by UHPLC-HRMS, 7 were identified by DART in the coating and in the concentrated
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acetonitrile extract, totaling 70 % of the compounds. However, only Cyclo-di-BADGE and
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BADGE+BPA+PrOH were detected in the non-concentrated ACN extract. Compounds that were
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not detected by DART (see Table 2), in the coating or in the concentrated ACN extract;
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correspond to oligomers with highest molecular weight. This pattern fits with expectations
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because high molecular weight (MW) compounds are usually less volatile at working
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temperatures and are therefore difficult to detect using DART-HRMS. In addition, we looked for
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the monomers BPA and BADGE. Using the negative mode, BPA was detected directly in the
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coating and in both acetonitrile extracts. BADGE was detected in the positive mode in the
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coating and in the ACN concentrated extract. Because direct identification in the coating gives
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results similar to those provided by other conventional techniques, our data suggest that DART is
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capable of identifying BADGE derivatives, BPA and BADGE within epoxy-resin coatings in
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minutes, without sample preparation.
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Method validation and stability test
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The method performance was characterized by correlation coefficient (r2 > 0.998); limits of
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detection (LOD) were calculated as three time the signal-to-noise of the blank reagents: 0.2
249
ng/mL for BGA to 50 ng/mL for BADGE.2H2O using HPLC-DAD at 220 nm. A limit of
250
quantitation of three times the LOD was used for all compounds. The relative standard deviation
251
(RSD) (%) (n = 5) was below 4.7. The proposed methods were accurate and sensitive. For BPA,
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HPLC-MS/MS was used because of compound confirmation purposes, ratio between transitions
253
had to match the standard within 25%.
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Because the specific BADGE derivatives we identified were not commercially available as
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standards, we needed to use available standards of BADGE-related compounds, in addition to
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BPA and BADGE, to validate the recovery of our concentration method. These compounds
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cover an acceptable mass range, and it was assumed that the BADGE derivatives we identified
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should behave similarly. Recoveries (mean (%) ± S.D (n=3-5)) from the food simulants ranged
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from 80 ± 6.7 for BPA in isooctane to 110 ± 2.2 for BADGE.H2O in 3% acetic acid,
260
demonstrating that our method was appropriate. We also performed a stability test to 120 days
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for BADGE and BPA into food simulants. Our data showed the stability of these analytes was
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above 80% at 120 days, demonstrating these compounds are stable in standard food simulants.
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For cans lined with epoxy-resins, specifically retorted cans containing water and cans containing
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50% ethanol, the concentration step was not necessary because migrating substances could be
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analysed directly in the simulant. This was also the case for certain migrating substances from
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acrylic-phenolic cans containing 50% ethanol. For the remaining cans, particularly cans which
267
were not retorted, the concentration step was necessary. Due to the high sensitivity of our
268
method for analysing BGA in cans lined with acrylic phenolic resin, we were able to analyse all
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simulants without a concentration step, except for isooctane, which was not analysed for BGA.
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Migration experiment
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Water based food simulant
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As shown in Table 3, the only identified epoxy-derivatives which migrated into the simulant in
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retorted epoxy-resin cans containing water were BADGE, BPA, and BADGE+BuEtOH+H2O.
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After 10 days there was no statistically significant increase in the concentration of any of the
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migrants. Similar patterns were observed for the set of unidentified migrants that have spectra
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distinctly different from BADGE derivatives: concentrations of Unknown 1 and Unknown 2
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remain stable during the study period (Data not displayed). For BPA, there is a small decrease in
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concentration, to 5.5 µg/dm2, observed at the last migration point, which corresponds to 490
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days. However, this small decrease in concentration does not have effect our assessment of
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migration test results.
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Very little migration of BPA or BADGE (≤ 0.6 µg/dm2) occurred in the retorted acrylic-phenolic
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cans containing water. Our data obtained by using the HRMS detector revealed that the BADGE 14 ACS Paragon Plus Environment
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migrates from the lid, so this low concentration was expected due to the small surface of the top
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of the can. Values for the target compounds also remained stable during the experiment (Table 3)
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as well as for tracked unknown migrants by DAD (Data not displayed). For example,
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concentration of BGA was 5.8 ± 0.5 and 4.9 ± 0.6 after 10 and 475 days migration respectively.
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This data illustrate that the equilibrium was reach after the thermal treatment in water and that
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the migrants remain stable in water during the short and long migration test.
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Among non-retorted cans, the only detectable concentrations of BPA were observed in epoxy-
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resin cans at the 10 day time point and thereafter. In contrast, BGA was only detected in cans of
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water food simulant lined with acrylic-phenolic coatings after 90 days. These results suggest that
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very little migration occurs into water food simulants in the absence of thermal treatment.
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Most of cans containing the 3% acid simulant failed. After exposure, cans were rusted and the
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coating degraded during the migration experiment due to the action of the simulant.
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Consequently, data was not included in the study because it does not represent a migration test
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simulating real conditions.
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50% ethanol and isooctane
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The results for the presence of monitored monomers in epoxy-lined cans containing 50% ethanol
299
results are reported in Table 4. Levels of BPA appear to reach equilibrium at about 90 days.
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However, most other tracked compounds seem to reach equilibrium at some point between 90
301
days and 305 days (Figure 2). Once mass transfer from the coating into the simulant is achieved,
302
most compounds remain stable during the migration time.
303
Our data illustrate that migration tests lasting 10 days at 40 °C do not estimate migration during
304
long term storage in 50% ethanol that have not been retorted. To confirm these results, we 15 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
305
conducted an additional test using two different types of epoxy can coatings: one yellow and the
306
other, white in colour. Our experiment was conducted using replicates and storage durations of 1,
307
10, 30 and 130 days at 40 °C using 50% ethanol. The profiles of migrants were monitored using
308
the DAD at 225 nm. For these assessments, we did not evaluate BADGE derivatives except the
309
characteristic cyclo-di-BADGE ; however, migrants having spectra equivalent to those of
310
BADGE derivatives could be tracked by the DAD. The obtained results are presented in Table
311
5. Results for the cans coated with yellow epoxy showed that equilibrium for BPA is reached at
312
the 30 day time point. We found that most of compounds eluting at the beginning of the
313
chromatogram, which are generally polar compounds having low molecular weight (MW), these
314
also reach equilibrium by 30 days (data not displayed). However, for cyclo-di-BADGE,
315
concentrations seem to continue to increase up to 130 days. This was also the case for other late
316
eluting compounds. These results could be explained because one of the parameters affecting the
317
diffusion process is the MW (molecular size) of compounds: migrants with high MW will
318
diffuse at a slower rate because they are larger molecules than the early migrants with low MW.
319
Data from the cans coated with white epoxy also illustrated an increase in migrant concentrations
320
up to 130 days. These findings imply that diffusion rates of specific epoxy coatings may vary
321
depending on each coating formulation and manufacturer: it is likely that the glass transition
322
temperature (Tg) of each coating has important role in the mass transfer of migrants, since at
323
working temperatures below Tg, the diffusion coefficient of migrants appears to slow down. We
324
hypothesize that migration tests at higher temperatures could provide better estimates of
325
migration in food and/or food simulants. Briefly, for all tested can coatings in 50% ethanol in
326
this experiment, migration did not reach equilibrium at 10 days at 40 °C, the typical testing
327
protocol. 16 ACS Paragon Plus Environment
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As shown in Table 4, the equilibrium point for the target compounds in acrylic-phenolic lined
329
cans, showed the same patterns as the epoxy-lined cans. The equilibrium for the target
330
compounds was reached between 90 and 180 days. Once the mass transfer has occurred, these
331
compounds levels remain stable. Because standards are available for BADGE and related
332
compounds, these monomers can be tracked accurately. However, for migrating compounds that
333
do not belong to the BADGE derivative family, while the absolute values may not be accurate
334
the relative values indicate the changes in concentration between time points. From the migration
335
perspective, they supply important information about how migration process occurs from the
336
acrylic-phenolic coating into the simulant.
337
None of the potential migrants were identified in the isooctane contained in non-retorted cans.
338
The lack of detectable migration of these compounds is consistent with the structure of the test
339
polymers and the monomers being polar and thus is partition limited into nonpolar simulant,
340
especially without a retort step.
341
Acetonitrile extraction of the coatings
342
We performed an extraction of the epoxy and acrylic coating using ACN by extracting the
343
coating three times at 40 °C for one day. Results are presented in bottom of Table 4. The
344
majority of the extraction of potential migrants took place during the first day.
345
For most of the target compounds in acrylic-phenolic coatings, the final concentration in the 50%
346
ethanol simulant was higher than in the acetonitrile extract. For example, at the 1.5 year time
347
point, Unknown D had an estimated concentration of 58 µg/dm2 in 50% ethanol and 16 µg/dm2
348
in the acetonitrile extract. While this can be explained by interactions between the simulants used
349
and the polymer coatings, these polymer coatings do not appear degraded or attacked to naked 17 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
350
eye inspection after the migration experiment concluded. This raises the possibility of hydrolysis,
351
which means oligomers of high MW could migrate into the simulant and subsequently could be
352
degraded into smaller compounds.
353
On the other hand, Table 4 also illustrates that, for epoxy-resins, most of the tracked BADGE
354
derivatives found in the food simulants are in concentrations equal or lower than the
355
concentrations found in the acetonitrile extract. For instance, concentration of BADGE+2BPA in
356
acetonitrile is 212 µg/dm2, versus 182 µg/dm2 in 50% ethanol, after 490 days. This means that
357
the observed increases in the concentration of tracked BADGE derivatives in 50% ethanol is
358
probably not due to a hydrolysis process of epoxy oligomers or the epoxy coating. The presence
359
of cyclo-di-BADGE supports this interpretation; because of its cyclic structure, it is not likely to
360
have been formed as a consequence of a hydrolysis. Yet the increases in cycle-di-BADGE
361
concentration observed during the extended storage time might be more likely because migration
362
occurs at a slower rate compared to other types of polymers. Two factors could be involved in
363
this phenomenon: the glass transition temperature of the coating and/or the structure of the
364
coating itself. It is known that polymers having glass transition temperatures above those of their
365
storage conditions remain in a glassy state, and consequently any potential migrants diffuse
366
much more slowly. Can coatings themselves are cross-linked polymers, which requires a longer
367
time for molecules to migrate from the inside of the coating toward the food simulant.
368
The marked compounds in epoxy coatings, unknowns 1 and 2, were not supposed be related to
369
epoxy since they had a spectrum with different molar absorption than epoxy derivatives; and
370
they achieved a significantly higher concentration in the 50% ethanol than in the ACN extract.
371
The high migration of these two unknown compounds could have occurred through hydrolysis of
372
non-epoxy derivatives compounds with high MW and/or the interactions between the food 18 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
373
simulant and contact polymers. A similar behaviour was observed for the tentatively identified
374
BADGE+BPA+H2O. This may mean that any hydrolysis processes involving most likely non-
375
epoxy substances may also liberate other hydrolytic compounds such as this oligomer.
376
When comparing BPA concentrations in epoxy-retorted cans containing water to the
377
concentrations in an ACN extract, the concentration of the monomer is lower in water. However,
378
for Unknowns 1 and 2, despite remaining constant during the experiment (average of 195 µg/dm2
379
Unknown 1 and 81 µg/dm2 for Unknown 2 in water), these levels are higher than in ACN: 104
380
µg/dm2 for Unknown 1 and 52 µg/dm2 for Unknown 2. This data suggest that interaction with
381
polymer and/or hydrolysis, may also occur with the aqueous simulant in this coating, but is
382
completed in the thermal treatment.
383
Although the migration data from cans containing 50% ethanol illustrate increasing
384
concentrations of migrants over time, for at least 90 days, even in the worst case migration
385
scenario (observed in the 50% ethanol condition) it is important to note that the concentration of
386
migrants such as BPA reported are still within the normal ranges of concentration previously
387
reported in the literature4, 24, 25. In addition, measured concentrations are clearly below the
388
specific migration limits set by the European Union 26.
389
CONCLUSION
390
In this study, we determined the identity of potential migrants from epoxy-resins and acrylic-
391
phenolic coatings and evaluated whether common migration testing procedures accurately
392
predict migration during long term storage. Several BADGE derivatives were identified and the
393
spectra of unknown migrants from epoxy and acrylic phenolic coatings were used for tracking
394
these compounds during the migration experiment. Future identification of these unknown 19 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
395
compounds is necessary in order to assess risk. DART-HRMS was applied to identify BADGE
396
derivatives and monomers (BPA and BADGE) in the coating obtaining similar results as in
397
acetonitrile extract. The use of DART-HRMS to identify potential migrants directly in the
398
coating avoids sample preparation and the development of traditional analytical methods, which
399
imply a significant improvement in identification of migrants. Conventional migration tests have
400
estimated mass transfer rates for extended time periods using aqueous food simulants,
401
particularly in cans subjected to a retort step. The concentrations of migrants into 50% ethanol
402
show an increase in concentration after ten days migration testing. However, once the mass
403
transfer is completed, migrants remain stable. This means that if mass transfer has not been
404
completed by the end of a traditional migration test period, migration of compounds could
405
continue beyond those measurement points. Such increases in concentration could be due a
406
variety of reasons, including a slow rate of diffusion from the coatings to the simulant, the glass
407
transition temperature of the coating, interactions between the simulant and the can coating,
408
and/or hydrolysis of certain migrants over extended periods. Our findings, along with those from
409
analyses of long term food simulant storage in cans lined with vinyl and polyester coatings12, 21,
410
suggest that migration protocols may need to be revised to properly represent what happens
411
during the long term storage of food products. Because there is little to no data available on the
412
long term interaction of foods with coatings, a logical next step would be to assess actual foods
413
after long term storage.
414 415 416 417
ACKNOWLEDGEMENT This project was supported in part by an appointment to the Research Participation Program at
418
the Center for Food Safety and Applied Nutrition, administered by the Oak Ridge Institute for
419
Science and Education through an interagency agreement between the U.S. Department of 20 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
420
Energy and the U.S. Food and Drug Administration. We thank Lili Fox Vélez, Ph.D. for her
421
scientific writing and editing support.
422 423
REFERENCES
424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461
1. Molina-Garcia, L.; Fernandez-de Cordova, M. L.; Ruiz-Medina, A., Analysis of Bisphenol A in milk by using a multicommuted fluorimetric sensor. Talanta 2012, 96, 195-201. 2. Arnich, N.; Canivenc-Lavier, M. C.; Kolf-Clauw, M.; Coffigny, H.; Cravedi, J. P.; Grob, K.; Macherey, A. C.; Masset, D.; Maximilien, R.; Narbonne, J. F.; Nesslany, F.; Stadler, J.; Tulliez, J., Conclusions of the French Food Safety Agency on the toxicity of bisphenol A. Int J Hyg Environ Health 2011, 214, 271-5. 3. Ackerman, L. K.; Noonan, G. O.; Heiserman, W. M.; Roach, J. A.; Limm, W.; Begley, T. H., Determination of Bisphenol A in U.S. Infant Formulas: Updated Methods and Concentrations. J. Agric. Food Chem. 2010, 58, 2307-2313. 4. Noonan, G. O.; Ackerman, L. K.; Begley, T. H., Concentration of Bisphenol A in Highly Consumed Canned Foods on the U.S. Market. J. Agric. Food Chem. 2011, 59, 7178-7185. 5. Bang, D. Y.; Kyung, M.; Kim, M. J.; Jung, B. Y.; Cho, M. C.; Choi, S. M.; Kim, Y. W.; Lim, S. K.; Lim, D. S.; Won, A. J.; Kwack, S. J.; Lee, Y.; Kim, H. S.; Lee, B. M., Human risk assessment of endocrine-disrupting chemicals derived from plastic food containers. Compr. Rev. Food Sci. Food Saf. 2012, 11, 453-470. 6. Bolognesi, C.; Castle, L.; Cravedi, J.-P.; Engel, K.-H.; Fowler, P.; Franz, R.; Grob, K.; Gurtler, R.; Husoey, T.; Mennes, W.; Milana, M. R.; Penninks, A.; Roland, F.; Silano, V.; Smith, A.; Pocas, M. d. F. T.; Tlustos, C.; Toldra, F.; Wolfle, D.; Zorn, H., Scientific opinion on the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs: executive summary. EFSA J. 2015, 13, 3978/1-3978/22, 22 pp. 7. http://www.fda.gov/food/ingredientspackaginglabeling/foodadditivesingredients/ucm064 437.htm 8. Pastorelli, S.; Beldi, G.; Simoneau, C., Effect of calibration standards on the quantification of hydroxy products from can coatings. Anal. Chim. Acta 2006, 557, 7-10. 9. Paseiro Losada, P.; Simal Lozano, J.; Paz Abuin, S.; Lopez Mahia, P.; Simal Gandara, J., Kinetics of the hydrolysis of bisphenol A diglycidyl ether (BADGE) in water-based food simulants. Implications for legislation on the migration of BADGE-type epoxy resins into foods. Fresenius' J. Anal. Chem. 1993, 345, 527-32. 10. Sendon Garcia, R.; Paseiro Losada, P., Determination of bisphenol A diglycidyl ether and its hydrolysis and chlorohydroxy derivatives by liquid chromatography-mass spectrometry. J. Chromatogr. A 2004, 1032, 37-43. 11. Munguia-Lopez, E. M.; Soto-Valdez, H., Effect of Heat Processing and Storage Time on Migration of Bisphenol A (BPA) and Bisphenol A-Diglycidyl Ether (BADGE) to Aqueous Food Simulant from Mexican Can Coatings. J. Agric. Food Chem. 2001, 49, 3666-3671. 12. Paseiro-Cerrato, R.; Noonan, G. O.; Begley, T. H., Evaluation of Long-Term Migration Testing from Can Coatings into Food Simulants: Polyester Coatings. J. Agric. Food Chem. 2016, 64, 2377-2385. 21 ACS Paragon Plus Environment
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13. Paseiro-Cerrato, R.; MacMahon, S.; Ridge, C. D.; Noonan, G. O.; Begley, T. H., Identification of unknown compounds from polyester cans coatings that may potentially migrate into food or food simulants. J. Chromatogr. A 2016, 1444, 106-113. 14. Schaefer, A.; Ohm, V. A.; Simat, T. J., Migration from can coatings: Part 2. Identification and quantification of migrating cyclic oligoesters below 1000 Da. Food Addit. Contam. 2004, 21, 377-389. 15. Schaefer, A.; Simat, T. J., Migration from can coatings: Part 3. Synthesis, identification and quantification of migrating epoxy-based substances below 1000 Da. Food Addit. Contam. 2004, 21, 390-405. 16. Biedermann, S.; Zurfluh, M.; Grob, K.; Vedani, A.; Bruschweiler, B. J., Migration of cyclo-diBA from coatings into canned food: Method of analysis, concentration determined in a survey and in silico hazard profiling. Food Chem. Toxicol. 2013, 58, 107-115. 17. Biedermann, M.; Grob, K., Food contamination from epoxy resins and organosols used as can coatings: analysis by gradient NPLC. Food Addit. Contam. 1998, 15, 609-618. 18. Biedermann, M.; Grob, K., Phenolic resins for can coatings: II. Resoles based on cresol/phenol mixtures or tert. butyl phenol. LWT--Food Sci. Technol. 2006, 39, 647-659. 19. Biedermann, M.; Grob, K., Phenolic resins for can coatings: I. Phenol-based resole analyzed by GC-MS, GC × GC, NPLC-GC and SEC. LWT--Food Sci. Technol. 2006, 39, 633646. 20. http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformati on/ucm081818.htm 8/19/2016 21. Vaclavikova, M.; Paseiro-Cerrato, R.; Vaclavik, L.; Noonan, G. O.; DeVries, J.; Begley, T. H., Target and non-target analysis of migrants from PVC-coated cans using UHPLC-QOrbitrap MS: evaluation of long-term migration testing. Food Addit. Contam., Part A 2016, 33, 352-363. 22. Bradley, E. L.; Driffield, M.; Harmer, N.; Oldring, P. K. T.; Castle, L., Identification of Potential Migrants in Epoxy Phenolic Can Coatings. Int. J. Polym. Anal. Charact. 2008, 13, 200223. 23. Berger, U.; Oehme, M., Identification of derivatives of bisphenol A diglycidyl ether and novolac glycidyl ether in can coatings by liquid chromatography/ion trap mass spectrometry. J. AOAC Int. 2000, 83, 1367-1376. 24. Munguia-Lopez, E. M.; Gerardo-Lugo, S.; Peralta, E.; Bolumen, S.; Soto-Valdez, H., Migration of bisphenol A (BPA) from can coatings into a fatty-food simulant and tuna fish. Food Addit. Contam. 2005, 22, 892-898. 25. Yonekubo, J.; Hayakawa, K.; Sajiki, J., Concentrations of Bisphenol A, Bisphenol A Diglycidyl Ether, and Their Derivatives in Canned Foods in Japanese Markets. J. Agric. Food Chem. 2008, 56, 2041-2047. 26. European Commission. 2011. Commission Regulation (EU) no 10/2011 of 14 January 2011 on plastic materials and articles intended to come into contact with food. Off J Eur Union. L 12:1–89.
505 506 22 ACS Paragon Plus Environment
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507 508 509 510 511 512 513
Journal of Agricultural and Food Chemistry
FIGURE CAPTIONS
Figure 1. FTIR spectra of the body of the employed epoxy-resin (above) and the body of the acrylic-phenolic coating (below)
514 0.24 0.22 0.20 0.18 0.16 0.14
Abs
0.12 0.10 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 4000
3500
3000
2500
515
2000
1500
1000
2000
1500
1000
cm-1
0.10 0.09 0.08 0.07 0.06
Abs
0.05 0.04 0.03 0.02 0.01 -0.00 -0.01 4000
516
3500
3000
2500 cm-1
517 518
23 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
519 520 521
Page 24 of 30
Figure 2. Migration of some BADGE derivatives into 50% ethanol from 1 day to 490 days in epoxy-resins cans.
522
50% Ethanol 350 300
µg/dm2
250 200 150 100 50 0 0
100 BADGE.2H2O
200
300 Time (days)
BADGE + BPA+H2O
Cyclo-di-BADGE
523 524 525 526 527 528 529 530 531 532 533 534 535 24 ACS Paragon Plus Environment
400
500 BADGE + 2BPA
Page 25 of 30
536
Journal of Agricultural and Food Chemistry
TABLES
537 538 539 540 541 542
Table 1. List of tracked characteristic marker compounds whose identity has not been confirmed by DAD but presented a large detector response in the detector. Rt = retention time in minutes.. nm = nanometers which correspond with the max in the spectra.
Unknowns
Coating
Rt
nm
Compound 1 Compound 2 Compound A Compound B Compound C Compound D Compound E Compound F Compound G
Epoxy-resins Epoxy-resins Acrylic phenolic Acrylic phenolic Acrylic phenolic Acrylic phenolic Acrylic phenolic Acrylic phenolic Acrylic phenolic
11 13.5 2.5 4 7 8 12 17.2 20.2
230, 262, 340 230, 262, 340 212, 228, 290 230, 266, 348 222, 286 248, 282, 332 222, 266, 246 228, 266, 348 242, 288
543 544 545 546 547 548 549 550 551 552 553 554 555 556 25 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
557 558 559 560 561 562 563
Page 26 of 30
Table 2. Identified BADGE derivatives in the tested epoxy coating using UHPLC-HRMS and DART-HRMS. The accurate mass is equivalent to the mass to charge ratio (m/z) of the identified compounds with the corresponding adduct. Rt = retention time (minutes) of the identified compounds detected using HPLC- DAD. ACNc = Acetonitrile extract from the epoxy can coating concentrated 25 to 1 mL.AcNT= Acetonitrile extract from the epoxy can coating. BuEtOH = butoxyethanol, PrOH = propanol, BuOH = buthanol.- = Not detected.
UHPLC-HRMS Proposed compounds BADGE+BuEtOH+H2O
m/z 499.2666
Adduct
DART
DAD (Rt)
Na+
Coating
9.6
+
BADGE+BPA+H2O
604.3269
NH4
11.1
BADGE+BuEtOH+HCl
517.2327
Na+
14.1
Cyclo-di-BADGE
586.3163
NH4+
BADGE+BPA+PrOH
646.3738
BADGE+2BuEtOH
594.4000
NH4
+
+
+
ACNc
AcNT
NH4
+
-
NH4
+
-
H+,H-
-
15.1
NH4 , H NH4+, H+,HNH4+, H+
NH4+, H+,H-
H+,H-
NH4+
17
NH4+
NH4+, H-
H-
NH4+
17.1
NH4+
NH4+
-
-
BADGE+BPA+BuEtOH
685.3746
H
18.5
-
-
-
BADGE+BPA+BuOH
660.3895
NH4+
19.1
NH4+
NH4+
-
-
BADGE+2BPA
795.3902
H
19.5
-
-
-
BADGE(n=1)+BPA+PrOH
911.4740
H-
-
-
-
-
564 565 566 567 568 569 570 571 572
26 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
Table 3. Migration results of the some migrants analyzed from the tested coatings into aqueous food simulant. BADGE+BuEtOH+H2O was detected by HPLC- MS. BPA by HPLC-MS/MS, BADGE.2H2O by HPLC-DAD at 225 nm and BGA by UHPLC-HRMS. Data expressed in µg/dm2.
Epoxy-resin Simulant Time (days)
Acrylic-phenolic
Water retort BPA
BADGE.2H2O
Simulant
BADGE+BuEtOH+H2O
Water retort
Time (days)
BPA
BADGE.2H2O
BGA
1
7 ± 0.8
14 ± 2
32 ± 10
1
0.14
0.6
6.9
10
7.2 ± 0.7
14 ± 0.1
35 ± 20
10
0.16 ± 0.06
0.6 ± 0.04
5.8 ± 0.5
30
8.4
16
34
90
0.15
0.5
6.1
90
6.3
14
28
180
0.13 ± 0.002
0.5 ± 0.02
6 ± 0.5
305
7.3 ± 0.4
14 ± 1
28 ± 3
330
0.17
0.5
6
490
5.5 ± 0.3
14 ± 0.4
18 ± 9
475
0.15 ± 0.01
0.6 ± 0.02
4.9 ± 0.6
Table 4. Migration results from the tested coatings into 50% ethanol food simulant. BADGE+BuEtOH+H2O, BADGE+2BuEtOH and BADGE + BPA+BuOH, were detected by HPLC- MS. BPA by HPLC-MS/MS and the rest of migrants by HPLC-DAD at 225 nm for epoxy cans. For acrylic phenolic cans, unknowns were detected by HPLC-DAD at 220 nm. BADGE.2H2O by HPLC-MS and BGA by UHPLC-HRMS. Acronyms of letters and numbers are presented in table 2.Data is expressed in µg/dm2.* analyzed as BADGE. ND- Not detected. NA-Not analyzed.
27 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Page 28 of 30
Epoxy-resin BPA
BADGE.2H2O
BADGE+BuEtOH +H2O
1
2.1 ± 0.5
ND
13 ± 3
10
6.8 ± 0.7
4.9
37 ± 1
Time (days)
BADGE + BPA+H2O
2
BADGE+Bu EtOH+HCl
46 ± 1
ND
22 ± 1
ND
CyclodiBADGE ND
158 ± 7
21 ± 1
88 ± 5
ND
61 ± 7
1
BADGE + BPA+PrOH
BADGE+2BuEtOH
BADGE + BPA+BuOH
ND
ND
19 ± 9
ND
ND
10 ± 1
28 ± 2
36 ± 4
BADGE + 2BPA
90
13
15
88
272
54
182
23
273
37
17
36.7
135
305
11 ± 1
21 ± 2
115 ± 2
330 ± 17
70 ± 2
217 ± 8
25 ± 2
303 ± 3
49 ± 1
20 ± 2
56 ± 8
172 ± 2
490
13 ± 2
23 ± 0.5
123 ± 6
360 ± 16
77 ± 3
239 ± 6
34 ± 4
325 ± 7
52 ± 8
22 ± 1
57 ± 3
182 ± 7
ACN extract
10
NA
NA
104
43
52
28
383
52
NA
NA
212
Time (days)
BPA
BADGE.2H2O
BGA
A
B
C
D
E
Acrylic-phenolic F
G
1
0.1
0.1
ND
10
10
ND
10
10
10
ND
10
0.2 ± 0.02
0.1
ND
10
10
ND
10
10
34 ± 3
10
90
0.7
0.8
1
10
30
10
34
10
68
14
180
1.8 ± 0.1
0.7 ± 0.1
12 ± 0.5
34 ± 6
59 ± 3
30 ± 2
56 ± 3
38 ± 2
102 ± 3
29 ± 6
360
1.9
0.6
9.3
32
52
28
56
42
95
21
475
2 ± 0.5
0.7 ± 0.1
12 ± 0.7
34 ± 1
62 ± 11
28 ± 1
58 ± 8
42 ± 3
107 ± 4
35 ± 1
ACN extract
0.5
0.3*
ND
4.5
14
ND
16
15
67
40
28 ACS Paragon Plus Environment
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Journal of Agricultural and Food Chemistry
Table 5. Migration of some of the tracked migrants into 50% ethanol from yellow and white epoxy cans by using HPLC-DAD at 225 nm. BADGE concentrations are the result of the addition of BADGE.H2O and BADGE.2H2O. Data expressed in µg/dm2. ND- Not detected.
Time
Epoxy can A (Yellow)
Epoxy can B (White)
Days
BPA
BADGE
Cyclo-diBADGE
BPA
BADGE
Cyclo-diBADGE
1
1.2
10
76
ND
10
43
10
2.8
31
188
ND
38
119
30
3.6
34
306
0.5
37
258
130
3.2
38
376
2.1
56
406
29 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
Long term migration from epoxy and acrylic-phenolic food cans
81x43mm (300 x 300 DPI)
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