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Polyphenylsulfone (PPSU) plastic for baby bottles: an example for a comprehensive analytical NIAS assessment based on polymer-related extractables and leachables

Poster

Polyphenylsulfone (PPSU) plastic for baby bottles: an example for a comprehensive analytical NIAS assessment based on polymer-related extractables and leachables

Abstract

Since polycarbonate basically consisting of bisphenol A (BPA) was banned for the production of baby bottles, the polyarylsulfone plastics polyethersulfone (PES) and polyphenylsulfone (PPSU) became promising alternatives. PES and PPSU are extremely resistant materials to chemical (acids/bases), mechanical and thermal treatments. PES and PPSU are formally composed of bisphenol S (BPS) as well as 4,4‘-dihydroxybiphenyl (DHBP). Based on their bisphenolic molecular structure, both substances might cause similar endocrine effects compared to the banned BPA. In our study, we analyzed commercially available PES and PPSU materials used for baby bottles. We focussed on the identification and quantification of polymer related substances, mainly monomer derivatives as well as oligomers with a molecular weight below 1.000 dalton, as potential migrants into baby food.
Polyphenylsulfone (PPSU) plastic for baby bottles:
an example for a comprehensive analytical NIAS assessment based on polymer-related
extractables and leachables.
Introduction
Since polycarbonate basically consisting of bisphenol A (BPA) was banned for the
production of baby bottles, the polyarylsulfone plastics polyethersulfone (PES) and
polyphenylsulfone (PPSU) became promising alternatives. PES and PPSU are
extremely resistant materials to chemical (acids/bases), mechanical and thermal
treatments. PES and PPSU are formally composed of bisphenol S (BPS) as well as
4,4-dihydroxybiphenyl (DHBP). Based on their bisphenolic molecular structure, both
substances might cause similar endocrine effects compared to the banned BPA.
In our study, we analyzed commercially available PES and PPSU materials used for baby
bottles.We focussed on the identification and quantification of polymer related
substances, mainly monomer derivatives as well as oligomers with a molecular weight
below 1.000 dalton, as potential migrants into baby food.
PES and PPSU polymers from different manufacturers were characterized by 1H-NMR, size exclusion chromatography and
RP-HPLC analysis with respect to their end groups, their average molecular weight and their oligomer content < 1.000 dalton.
PES and PPSU oligomers were identified by LC-ESI(+)-MS and (semi-) quantified based on the chromophore concentration
using the commercially available reference substance BPS at a specific UV-wavelength.
Migration tests according to EU (VO) No.10/2011 with food simulant for milk (50% EtOH) were performed. Neither SML values for
listed monomers nor TTC thresholds for not listed monomers and oligomers were exceeded.
Based on our studies, baby bottles made from PES or PPSU materials can be evaluated as safe
alternatives for polycarbonate with regard to the migration of polymer related substances.
References Data published: Eckardt et al., 2018. Food Addit Contam Part A. DOI: 10.1080/19440049.2018.1449255
[1] Schaefer et al., 2004. DOI 10.1080/02652030310001637939
[2] EFSA 2016. DOI: 10.2903/j.efsa.2016.4357
1H-NMR Average molecular weight & analysis of end groups HPLC-SEC Oligomers below 1.000 dalton
Conclusion
Martin Eckardt*, Annemarie Greb, Thomas Simat
Chair for Food Chemistry and Food and Skin Contact Materials, Technische Universität Dresden, Germany
* mail: martin.eckardt@chemie.tu-dresden.de
Polymer production and structures
    
    
Polyarylsulfones like PES and PPSU are usually prepared by
polycondensation of the chlorinated BPS derivative 4,4-dichloro-
diphenylsulfone (short Cl-BPS-Cl) with BPS (PES) or DHBP (PPSU)
in an aprotic polar solvent such as N-methylpyrrolidine (NMP) or
sulfolane.
By final addition of chloromethane, the hydroxyl end groups of the
linear polymer chains are partially methoxylated.
- 27th March 2018, ILSI Europe, Brussels, Belgium -
 
Chromophore concentration
Poster online
12.9 13.1 12.8 12.1
13.7 14.2
16.7
14.6
21.5
0.4 0.4
2.2
0.5
6.4 7.2
0.4 0.4
2.1
PPSU-G1
PPSU-F1
PPSU-G2
PPSU-F2
PPSU-G3
PPSU-F3
PPSU-G4
PPSU-F4
PES-G1
0
5
10
15
20
Average molecular weight [kDa]
Average molecular weight
0
5
10
15
Ratio of endgroups: -OMe/-Cl
Endgroup ratio: -OMe/-Cl
(A) (B)
Polymer structures of PES (A) and PPSU (B). PES exclusively consists of repeating units of BPS, whereas BPS and DHBP units alternate in the
PPSU polymer. Polymer end groups Rcan be hydroxylated (OH), chlorinated (Cl)or methoxylated (OMe).
Total polymer characterization
1H-NMR (600 MHz) of completely dissolved PPSU polymers in CDCl3.
Determination of average molecular weight and ratio of endgroups (-OMe/-Cl). Results of 1H-NMR analysis. Minor differences in average molecular weight, but big
differences in the ratio of methoxylated (-OMe) and chlorinated (-Cl) endgroups.
3.73.83.96.86.97.07.17.27.37.47.57.67.77.87.98.08.1 ppm
PPSU: High -Cl content
PPSU High -OMe content
AB
C
C
A
B
Identification and determination of linear and cyclic PES/PPSU oligomers after solvent extraction
Oligomer quantification: Chromophore concentration Extracts: Monomer derivatives and oligomers < 1.000 dalton
0 2 4 6 8 10 12 14 16 18 20 22 24
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
M4 M5
M3
M2
C3
D3
T1
D2
C7
C6
C5
M1
UV 255 nm [mV]
Retention time [min]
PES-G1 C4
T2
Q1 Q2
T3
Monomer derivatives (M)
Oligomers (C/D/T/Q)
0 2 4 6 8 10 12 14 16 18 20 22 24
0
10
20
30
40
50
60
70
O12
O13
O11
O7
O8
O6
O5
O2
O1
M9
M4
M7
M3 M5
M8
UV 255 nm [mV]
Retention time [min]
PPSU-G1
PPSU-G3
M6
Monomer derivatives (M)
Oligomers (O)
O9
O10
1000 Da cut
RP-HPLC chromatogram (UV 255 nm)of a milled PES material after
solvent extraction (conditions: acetonitrile, 1h, 120°C).
11 12 13 14 15 16 17 18 19 20 21
0
1
2
3
4
5
6
7
8
9
10
10 11 12 13 14 15 16 17 18 19 20 21 22 23
0
50
100
150
200
250
300
350
400
Intensity 275 nm [mV]
Elution [mL]
Oligomer
< 1.000 Da
Oligomer
Polymer
Polymer
Intensity 275 nm [mV]
Elution [mL]
PPSU-G3
PES-G1
Baseline
Size exclusion chromatography (HPLC-SEC) of completely dissolved polymers.
Estimation of relative oligomer content below 1.000 dalton.
0.50 0.47
0.56
0.51 0.47 0.47
0.38 0.46 0.47
PES
PPSU-G1
PPSU-F1
PPSU-G2
PPSU-F2
PPSU-G3
PPSU-F3
PPSU-G4
PPSU-F4
PES-G1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Oligomers below < 1000 Da [%]
Relative oligomer content < 1.000 dalton determined by HPLC-SEC. Minor
differences between the polymers. Average oligomer content ~ 0.5 %.
RP-HPLC chromatograms (UV 255 nm)of two milled PPSU materials after
solvent extraction (conditions: acetonitrile, 1h, 120°C).
# Typ Struktur M
[g/
mol
]
ACN,
1h, 120
°
C [mg/kg]
EtOH
1h, 120
°
C [mg/kg]
50% EtOH
1h, 120°C [mg/kg]
M1
Monomer
BPS 250.3 ~ 0.3 (NWG) ~ 0.3 (NWG) ~ 0.3 (NWG)
M2
Monomer
BPS-OMe 264.3 2 1 0.5
M3
Monomer
MeO-BPS-OMe 278.3 20 6 2
M4
Monomer
Cl-BPS-OMe 282.7 111 48 14
M5
Monomer
Cl-BPS-Cl 287.1 184 53 11
C3 Cyclic C[BPS]3 696.8 854 148 39
C4 Cyclic C[BPS]4 929.1 2483 357 52
C5 Cyclic C[BPS]5 1161.4 969 119 10
D1 Linear
MeO
-[BPS]2-
OMe
510.8 n.A. n.A. n.A.
D2 Linear Cl-[BPS]2-OMe 515.0 122 36 8
D3 Linear Cl-[BPS]2-Cl 519.4 33 12 3
T1 Linear
MeO
-[BPS]3-
OMe
742.8 149 36 8
T2 Linear Cl-[BPS]3-OMe 747.2 143 34 6
T3 Linear Cl-[BPS]3-Cl 751.7 n.A. n.A. n.A.
Q1 Linear
MeO
-[BPS]4-
OMe
975.1 n.A. n.A. n.A.
Q2 Linear Cl-[BPS]4-OMe 979.5 n.A. n.A. n.A.
Table: Extraction results of milled PES-1 material after extraction with
different solvetns (ACN, EtOH, 50% EtOH, each 1h, 120°C).
# Typ Struktur M
[g/mol]
PPSU
-
G1
[mg/kg] PPSU-G2
[mg/kg]
PPSU
-
G3
[mg/kg]
M6
Monomer
DHBP 186.2 2 2 3
M3
Monomer
MeO-BPS-OMe 278.3 n.A. 1 4
M7
Monomer
DHBP-OMe 200.2 2 7 12
M4
Monomer
Cl-BPS-OMe 282.7 10 14 70
M5
Monomer
Cl-BPS-Cl 287.1 9 8 31
M8
Monomer
MeO-DHBP-OMe 214.3 2 10 195
M9
Monomer
Biphenyl 154.2 11 n.d. n.d.
O6 Cyclic C[BPS+DHBP]2 801.0 1241 1406 971
O1 Linear MeO-[BPS+DHBP]-OMe 446.5 16 94 42
O2 Linear Cl-[BPS+DHBP]-OMe 450.9 284 216 151
O5 Linear Cl-[BPS+DHBP+BPS]-Cl 687.6 712 245 11
O7 Linear MeO-[DHBP+BPS+DHBP]-OMe 614.7 62 485 639
O8 Linear MeO-[BPS+DHBP]2-OMe 846,9 31 204 70
O9 Linear Cl-[BPS+DHBP]2-OMe 851,4 397 281 187
O10
Linear Cl-[BPS+DHBP]2+BPS-Cl 1088.1 822 281 5
O11
Linear MeO-[DHBP+BPS]2+DHBP-OMe 1015.2 90 636 809
O13
Linear MeO-[DHBP+BPS]3+DHBP-OMe 1415.6 n.A. n.A. n.A.
Table: Total extraction of monomer derivatives and oligomers from three
different PPSU materials. Each 10 times consecutive acetonitrile, 1h, 120°C.
A) UV spectra of commercially available as well as self-synthesized chlorinated and methoxylated monomer derivatives of DHBP
and BPS. Almost equal molar absorbance (±7%) of all derivatives at 255 nm. Usage of 255 nm as specific wavelength for
quantification of linear and cyclic PES/PPSU oligomers based on the chromophoric concentration as reported by SCHÄFER[1].
B) Linear calibration curves of all monomer derivatives of BPS and DHBP at the common wavelength of 255 nm. Usage of the
linear regression curve of the commercially available reference substance BPS for the quantification of PES/PPSU oligomers.
Cl-BPS-OMe (M4)
Cl-BPS-Cl (M5)
DHBP-OMe (M7)
MeO-DHBP-OMe (M8)
Cl-[BPS]2-OMe (D2)
Cl-BPS+DHBP-OMe (O2)
C
D
C) Structural examples of monomer derivatives (Mx)of BPS and DHBP with chlorinated,
methoxylated and hydroxylated end groups.
D) Structural examples of linear and cyclic PES (Dx)und PPSU oligomers (Ox).
C[BPS+DHBP]2 (O6)
y = 98.975x
y = 114.34x
0
2000
4000
6000
8000
10000
12000
14000
020 40 60 80 100 120
Area (255 nm) * M [mV*min*g/mol]
Concetration [mg/L]
BPS
DHBP
BPS-OMe
MeO-BPS-OMe
DHBP-OMe
MeO-BPS-Cl
Cl-BPS-Cl
MeO-DHBP-OMe
B
215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
molar extinction [AU*L/mmol]
Wavelength [nm]
BPS (M1)
BPS-OMe (M2)
MeO-BPS-OMe (M3)
Cl-BPS-OMe (M4)
Cl-BPS-Cl (M5)
DHBP (M6)
DHBP-OMe (M7)
MeO-DHBP-OMe (M8)
equal absorbance
at 255 nm
A
Specific migration limit (SML)
EU (VO) 10/2011 * NIAS evaluation according to
Threshold of Toxicological Concern (TTC)
BPS (M1) 50 µg/kg food simulant Not listed monomers 10 µg/kg food simulant **Cl-BPS-Cl (M5) Linear oligomers
DHBP (M6) 6 mg/kg food simulant Cyclic oligomers
Results of migration tests according to EU (VO) 10/2011. 3 times consecutive migration into 50% EtOH (2h, 70°C).
Migration of monomer derivatives as well as oligomers from PPSU (A) and PES (B) bottles. (LOD: ~0.1 µg/kg).
Migration into food simulants Risk assessment
50% ethanol in water, 2h, 70°C, 3 times consecutive
        
        
PPSU-F3
DHBP
DHBP-OMe
MeO-DHBP-OMe
MeO-BPS-OMe
Cl-BPS-OMe
Cl-BPS-Cl
O5 (Linear)
O6 (Zyklisch)
O7 (Linear)
DHBP
DHBP-OMe
MeO-DHBP-OMe
MeO-BPS-OMe
Cl-BPS-OMe
Cl-BPS-Cl
O5 (Linear)
O6 (Zyklisch)
O7 (Linear)
PPSU-F2
0
1
2
3
4
5
6
7
8
9
10
0.08 0.19 0.08 0.17 0.52 0.11 0.43 0.27 0.60
7.42
2.28 1.87
0.63 0.21 0.28
Cramer III threshold
<LOD
<LOD
<LOD
concentration in food simulant [µg/kg]
Migration 1
2 h, 70°C, 50 % EtOH,
Content per bottle: 300 mL
Migration 2
Migration 3
BPS
MeO-BPS-OMe
Cl-BPS-OMe
Cl-BPS-Cl
C4
PES-F1
0
1
2
3
4
5
6
7
8
9
10
2.10
3.98
0.93 1.52
concentration in food simulant [µg/kg]
<LOD
A B
*Specific migration limit (SML). Evaluation of the third migration after three times
consecutive migration into food simulant for milk (50% ethanol, 2h, 70°C).
** Evaluation of not listed (10/2011) monomer derivatives of BPS and DHBP as well
as the linear and cyclic oligomers based on the TTC concept (TTC threshold for
Cramer III substances: 1.5 µg/kg bw & day).
Calculation of Cramer III threshold based on EFSA[2]: 3 kg baby bodyweight,
daily intake: 150 mL/kg bw
Cramer III threshold: 10 µg/kg food simulant.
Publication
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Article
Polyphenylsulfone (PPSU) is a new material for the production of baby bottles. PPSU is a polyether plastic formally composed of bisphenol S (BPS) and 4,4ʹ-dihydroxybiphenyl (DHBP), which both have slight endocrine activities in in-vitro-tests. So far, little is known about the presence and the release of potentially hazardous substances from PPSU baby bottles. In our present study, we present a three step approach for the analysis of PPSU starting with polymer characterization in terms of chemical structure, total oligomer content and hydrolytic stability. Second is the determination of extractables focussing on monomers, monomer derivatives, linear and cyclic oligomers below 1000 dalton (Da) and residual solvent. Third is a risk assessment on migration-related substances in accordance to EU plastics regulation No 10/2011 based on triplicate consecutive migration experiments using official milk simulant 50% ethanol. We analysed five types of PPSU baby bottles from different brands as well as corresponding raw materials from different manufacturers by various analytical techniques (HPLC-DAD/FLD/Corona/ESI-MS, HPLC-SEC, GC-MS, ¹H-NMR). We found significant variations of PPSU materials from different producers with regard to polymer and oligomer chain end groups (methoxylation, chlorination), while total oligomer content below 1000 Da was similar (mean about 0.48%). BPS was not detected above 0.3 mg/kg polymer in any PPSU sample. Residual DHBP content ranged between 1.7 and 15.5 mg/kg polymer. The most common oligomer in all PPSU samples was the cyclic tetramer (about 1200 mg/kg polymer), which is the only cyclic compound below 1000 Da. Residual solvent, sulfolane, was determined to a maximum of 1300 mg/kg polymer. In migration tests, we detected exceedances of neither specific migration limits (SML) for listed substances nor of thresholds of toxicological concern (TTC) for non-listed substances (monomer derivatives, oligomers). Based on our analytical results, no concerns exist regarding migration of polymer-related substances from PPSU baby bottles.
Article
Metal cans for food use can be coated with lacquers based on polyester resins. Recent research has focussed on the identification and quantification of migrants released by coatings that are potentially absorbable (below 1000 Da). The presented method describes a procedure that was optimized to hydrolyse the polyester migrants into their monomers, polyvalent acids and polyols. The polyols were identified by gas chromatography with flame ionization detection GC-FID and the acids by high-performance liquid chromatography (HPLC) coupled with an ultraviolet and an electrospray ionization-mass selective detector (HPLC-ESI-MSD/UVD), respectively. With the knowledge of the polyester monomers, it was possible--at least tentatively--to identify the main components in the migrate as cyclic oligoesters by HPLC-ESI-MSD/UVD. A cyclic oligomer, CYCLO [3IPA (isophthalic acid) 3EG (ethylene glycol)] was synthesized and characterized by infrared, nuclear magnetic resonance and mass spectrometry as well as by elementary analysis for further confirmation. To determine the amount of migrating cyclic oligoesters, the response of the migrating substances was compared using different detectors, UVD, MSD and evaporative light scattering detector (ELSD). The response of the ELSD was dependent on the molecular weight of the analytes that reduced the accuracy of this detection type. The wavelength with the same absorption coefficient for IPA and terephthalic acid (TPA) was obtained at 232 nm. The UV(232nm) response of an oligoester is proportional to the number of its IPA/TPA moieties, which was verified for several TPA/IPA esters. The amount of the migrating oligoesters was determined using an UV(232nm) calibration of a commercially available TPA ester and the number of IPA/TPA moieties molecules gained from the ESI-MSD spectra. According to this method, the amount of migrating oligoesters below 1000 Da in the 95% ethanol migrate varied from 0.1 to 0.6 mg dm(-2) (0.6-3.6 mg kg(-1) food) in the examined coatings. The determined amounts account for about 50% of the total migrate below 1000 Da.