Application Note No. 119/2013 Determination of bisphenol A in preserved food SpeedExtractor E-916: Determination of bisphenol A in preserved food

Transcription

1 Application Note No. 119/2013 Determination of bisphenol A in preserved food SpeedExtractor E-916: Determination of bisphenol A in preserved food using the SpeedExtractor E-916

2 1 Introduction Bisphenol A (BPA) or 4,4'-(propane-2,2-diyl)diphenol, pictured in Figure 1, is the raw material for the production of polycarbonate (PC). Polycarbonate is a plastic which is used for example in baby bottles and coatings for different food containers. BPA is also an additive for flame retardants. In the presence of hot water or high ph bisphenol A is hydrolyzed out of polycarbonate. Therefore the legal sum of migration level (SML(T)) for BPA in food is a maximum of 0.6 mg/kg food [1]. Figure 1: Structural formula of bisphenol A The toxicology of bisphenol A and the human exposition towards this substance is discussed controversially in the last years. The EFSA (European Food Safety Authority) and the BfR (Federal Institute for Risk Assessment, Germany) recommend a tolerable daily intake (TDI) in humans of 0.05 mg/kg body weight [2, 3, 4]. Regardless of the toxicological evaluation, the control of canned food is important. Normally, preserved food is sterilized at 121 C after filling. This means during the sterilization process BPA could be released from the polycarbonate coating. Therefore a reliable and fast analysis method for different food matrices has to be introduced. In the following work the samples are homogenized, freeze dried and subsequently extracted using the SpeedExtractor E Equipment SpeedExtractor E-916, 2-port, 10 ml cells Column, Phenomenex Synergy Fusion RP80, 4 µm, 150 x 2.0 mm Mass spectrometer, Thermo TSQ Quantum Ultra AM Quartz sand (e.g. Merck, order no , additionaly extracted) Extraction thimbles (Whatman non-stick thimbles, order no ) Bottom filter SpeedExtractor E-916 (BUCHI ) Top filter SpeedExtractor E-916 (BUCHI ) 0.45 µm PTFE filter (e.g. Roth, order no. P816.1) 3 Chemicals and materials Chemicals: Acetonitrile HPLC grade (e.g. Roth order no ) Water HPLC grade (e.g. TKA GenPure UV-TOC, order no ) Internal standard (CIL bisphenol A, ring 13 C 12, order no. CLM , 100 ng/µl in methanol) For safe handling please pay attention to all corresponding MSDS. Application Note 119/2013 November /7

3 Samples: Beans, freeze dried Poultry soup stew, freeze dried Canned ravioli, freeze dried Artichokes, freeze dried The samples were purchased at a local supermarket. 4 Procedure The determination of bisphenol A in preserved food includes the following steps: Separate the liquid from the canned food Homogenization of the remaining solid fraction by shaking or grinding depending on the matrix Freezing and storing the samples in a PE container Freeze drying the samples, using Heto Drywinner Type DW6-85 Extraction of the samples, using the SpeedExtractor E-916 Clean-up, using a 0.45 µm PTFE syringe filter LC-MS analysis with Thermo TSQ Quantum Ultra AM 4.1 Freeze drying Freeze dry the samples with Heto Drywinner Type DW6-85 using the following conditions: Temperature: -100 C Pressure: < 0.3 hpa Duration: 96 hours Store the freeze dried samples in a round-bottomed flask with ground joint 4.2 Extraction method samples 1. Preheat the SpeedExtractor E-916 according to the parameters listed in Table 1 2. Mix 0.8 g of each freeze dried sample with 11 g quartz sand (pre-extracted and dried) 3. Prepare each 10 ml cell using a bottom cellulose filter 4. Fill each 10 ml extraction cell with the mixed sample 5. Add 10 µl of internal standard ( 13 C 12 bisphenol A) 6. Cover the cell content with a cellulose top filter 4.3 Extraction method blank 1. Preheat the SpeedExtractor E-916 according to the parameters listed in Table 1 2. Prepare each 10 ml cell using a bottom cellulose filter 3. Fill pre-extracted quartz sand into the 10 ml extraction cell 4. Add 10 µl of internal standard ( 13 C 12 -bisphenol A) 5. Cover the cell content with a cellulose top filter Application Note 119/2013 November /7

4 Table 1: Parameters for the extraction with E-916 Method parameters for the SpeedExtractor E-916 Pressure 100 bar Temperature 100 C Cell 10 ml Solvent Acetonitrile:Water-HPLC grade (50:50) Vial 60 ml No. of cycles 4 (4 th cycle post-extraction) Heat-up 1 min Hold 15 min Discharge 2 min Vial change After 3 rd cycle 4 th cycle collected in new vial Flush with solvent 1 min Flush with gas 3 min Total extraction time 1 h 15 min 4.4 LC-MS method parameters Filter an aliquot of each sample extract through a 0.45 µm PTFE syringe filter before the analysis with LC-MS. The chromatography is done in following: Column: Phenomenex Synergy Fusion RP80, 4 µm, 150 x 2.0 mm Flow: 600 µl/min Injection volume: 20 µl The gradient is listed in Table 2. Table 2: Gradient for the chromatography Time [min] % A (acetonitrile) % B (water HPLC-grade) Mass spectrometer: Thermo TSQ Quantum Ultra AM Ionization: APCI (negative) The measurement in the MS/MS mode (2 transitions for BPA and 13 C 12 -BPA each) is listed in Table 3. Table 3: Measurement in the MS/MS mode Interface Transition 1 (target) Transition 2 (qualifier) BPA C 12 -BPA For the quantification, a standard serial solution with 10 different concentrations is prepared (concentration area 1 ng/ml 500 ng/ml) and analyzed. For the internal calibration the standard solutions are fortified with a defined amount of 13 C 12 -bisphenol A. The evaluation is done using a second-order calibration function. Application Note 119/2013 November /7

5 To illustrate this, Figure 2 shows the total ion current (TIC) from the artichoke sample. The internal standard corrects for the losses during the sample preparation. RT: Relative Abundance RT: 1.87 MA: NL: 6.69E3 TIC F: - c APCI SRM ms @cid27.00 [ , ] MS _ RT: 1.87 MA: NL: 3.62E4 TIC F: - c APCI SRM ms @cid27.00 [ , ] MS _ Time (min) Figure 2: Both chromatograms show the total ion current (TIC) from the artichoke sample. The upper chromatogram shows the native bisphenol A mass trace and the lower chromatogram the TIC of the internal standard 13 C 12-bisphenol A. The internal standard acts like the native BPA which means it has the same chemical properties and the same retention time but a different mass. 5 Results 5.1. Bisphenol A determination in preserved food The results of the determination of bisphenol A in preserved food are presented in Table 4. The results are denoted in ng/g dry substance. Table 4: Results of the determination of bisphenol A in preserved food Beans (n=3) Poultry stew (n=3) Artichokes (n=3) Ravioli (n=6) Batch Batch Batch Batch Batch Batch Good relative standard deviations (rsd) between 6 % to 12 % for the determinations in triplicate and a rsd of 7 % for the sixfold determination are shown in Table 5. Table 5: Reproducibility of the analytics of bisphenol A in preserved food Beans Poultry stew Artichokes Ravioli Mean [ng/g dry substance] rsd [%] Application Note 119/2013 November /7

6 5.2 Post-extractions In the post-extraction runs no bisphenol A was detected above the limit of quantification (LOQ). The average amount of BPA for example in the bean sample was 709 ng/g dry substance. With an LOQ of 35 ng/g a residual amount of bisphenol A less than 5 % (4.9 %) may be present in this sample. Therefore the extraction can be considered as complete. In Figure 2 the determination of bisphenol A from the four preserved food samples is shown. The broken line depicts the LOQ of bisphenol A. ravioli artichokes poultry stew beans extraction 6 extraction 5 extraction 4 extraction 3 extraction 2 extraction bisphenol A in dry substance [ng/g] Figure 2: Determination of bisphenol A in different food samples. The broken line shows the LOQ (limit of quantification) of bisphenol A. 6 Conclusion The determination of bisphenol A in canned food samples using the SpeedExtractor E-916 provides reliable and reproducible results. Based on the fact that the amount of bisphenol A in the post-extractions was below the LOQ, extraction yields can be considered as complete. 7 Acknowledgement We sincerely thank Dr. Martin Schlummer and Ludwig Gruber and their analytical team from the Frauenhofer-Institut Verfahrenstechnik und Verpackung, Freising Germany. 8 References [1] Directive 2004/19/EC of 1 March 2004 amending Directive 2002/72/EC relating to plastic materials and articles intended to come into contact with foodstuffs [2] European Comission (Institute for Health and Consumer Protection): European Union Risk Assessment Report, 4,4'-isopropylidenediphenol (bisphenol-a), 2003 [3] EFSA: Scientific Opinion on bisphenol A: evaluation of a study investigating its neurodevelopmental toxicity, review of recent scientific literature on its toxicity and advice on the Danish risk assessment of bisphenol A, 2010 [4] BFR: Ausgewählte Fragen und Antworten zu Bisphenol A in verbrauchernahen Produkten, 2012 Operation Manual of SpeedExtractor E-916 Application Note 119/2013 November /7

7 9 Annex The quartz sand was pre-extracted and dried prior to the extractions. The conditions for the pre-extraction are as follows: Solvents: 2-propanol:dichloromethane:n-hexane (1:1:1, v:v:v) Temperature: 100 C Pressure: 100 bar No. of cycles: 4 The conditions for the drying after pre-extraction are: Dry overnight in a fume hood Store in a desiccator until extracting the samples Application Note 119/2013 November /7