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Application News Figure 1: ICPMS-2030 Elemental Analysis / ICPMS-2030 Evaluation of heavy metal migration from plastic food packaging materials to aqueous simulants by ICP-MS No. AD-0207 ❑ Overview Heavy metal migration from different types of plastic food packaging materials was studied. The packaging materials were immersed into several mimic food solutions according to EU legislation to simulate the process of heavy metal migration onto foodstuffs. The concentrations of 14 metallic elements in aqueous simulants were accurately determined by the developed ICP-MS method. The migration of elements was observed to increase with contact time. The presence of heavy metals, especially toxic elements such as Pb, highlighted the importance of quality control measures for food packaging materials. ❑ Introduction Food packaging materials that contact with food directly may cause food contaminations due to toxic substances and elements leaching out and migrating onto the food. Plastics are heavily used in food packaging in the modern food industry. Heavy metal contamination caused by plastic packaging materials is one of the significant concerns in food safety [1]. Thus, accurately determining heavy metal migration from food packaging material is essential to evaluate the potential health hazards to humans. Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool to investigate the elemental migration from food packaging material due to its low detection limits, relatively few interferences and multi-element capacity. In this work, the release of heavy metals onto foodstuffs were evaluated by immersing the testing plastic packages in food simulants including pure water, 2% nitric acid and 3% acetic acid. 14 heavy metals (Al, As, Ba, Cd, Co, Cr. Cu. Fe, Li, Mn, Ni, Pb, Sb and Zn) in the leaching solutions were determined simultaneously by a high sensitivity ICP-MS method. The effect of contact time on heavy metal migration was investigated using the food simulants. Raymond Li, Xinrong Lee * & Zhaoqi Zhan ❑ Experimental Three different types of plastic food packages including polystyrene (PS) container, polypropylene (PP) container and polyethylene (PE) film were obtained from local food markets. 0.5 grams of each packaging material were weighed and immersed into 40 mL of aqueous solutions for heavy metal leaching at room temperature. The aqueous solutions used as leaching solvents were DI water (simulant A), 3% acetic acid (simulant B) [2] and 2% nitric acid. After immersion, 1 mL of soaking solution was taken out and 1 mL of 3% acetic acid was added before dilution to 10 mL as the analysis solution. Multi-element calibration standards were prepared up to 50 ppb (Al, As, Cd, Co, Mn, Ni, Sb) or 200 ppb (Ba, Cr, Cu, Fe, Li, Pb, Zn) in 0.3% w/v acetic acid from single element stock solutions (1000 mg/L). Concentrations of the 14 toxic and interest elements were determined by ICP-MS with internal standard correction. The internal standard solution containing Sc, Y, Rh and Bi were added using an online internal standard addition kit. *Student for internship training program from Department of Chemistry, National University of Singapore Sample and Standards Preparation Analytical Conditions All analyses was carried out on Shimadzu ICPMS-2030 coupled with mini torch and AS-10 autosampler. The detailed instrument configuration and operation parameters were summarized in Table 1. Helium collision cell provides an effective way to remove possible polyatomic spectral interferences. The cell gas mode was applied for all the elements except for Li and Sb as shown in Table 2. The instrument was tuned and optimized using a mixed tuning solution and warmed up to 30 minutes before measurement.
Application News No. AD-0207 Element Mass Internal Standard Cell gas r LOD (μg/L) LOQ (μg/L) Al 27 Sc On 0.99992 0.201 0.670 As 75 Y On 0.99996 0.005 0.018 Ba 138 Rh On 0.99993 0.005 0.016 Cd 112 Rh On 0.99999 0.001 0.004 Co 59 Sc On 0.99999 0.001 0.002 Cr 53 Sc On 1.00000 0.013 0.044 Cu 65 Y On 0.99998 0.123 0.410 Fe 57 Sc On 0.99998 0.104 0.348 Li 7 Sc Off 0.99997 0.064 0.213 Mn 55 Sc On 0.99995 0.008 0.027 Ni 62 Y On 0.99999 0.067 0.223 Pb 208 Bi On 0.99999 0.123 0.411 Sb 123 Y Off 0.99999 0.001 0.002 Zn 68 Y On 0.99996 0.073 0.243 Table 2: Analyte masses, acquisition modes, calibration correlation coefficients, LODs and LOQs Parameter Setting RF Frequency Power 1.20 kW Sampling Depth 6.0 mm Plasma Gas Ar 8.0 L/min Auxiliary Gas Ar 1.10 L/min Carrier Gas Ar 0.70 L/min Torch Mini-Torch, ICPMS Nebulizer Nebulizer, 07UES Chamber Cyclone Chamber Chamber Temperature 5 o C No. of Scans 10 times Cell Gas (He) 6.0 mL/min Cell Voltage -21.0 V Energy Filter 7.0 V Solvent Rinse Time 10 sec (Low), 30 sec (High) Sample Rinse Time 30 sec (Low), 40 sec (High) Table 1: Analytical conditions and parameters of ICPMS-2030 Migration of heavy metal from plastic packaging materials Heavy metal migration from the three plastic packaging materials into food simulant B after soaking for 72 hours were determined and compared in Table 4. The leaching amounts were in ppb levels, but varied largely for different plastic packages. For example, for the PE film, the most leached element was zinc, followed by iron and aluminium with concentrations of 685.5, 142.5 and 135.5 μg/L, respectively. While for PS and PP container, the most leached element was aluminium, followed by zinc and copper. Migration of cobalt and lithium were not detected for any plastic materials. With regards to the toxic elements, arsenic and lead were detected with concentration ranges of 0.06 – 0.48 μg/L and 0.19 – 3.27 μg/L. Cadmium leaching was not found from PS and PP container, but 0.26 ug/L was detected from PE film. The measured concentrations shown in Table 4 are much lower than the restriction levels for Ba, Co, Cu, Fe, Li, Mn and Zn defined in EU No 10/2011 [2]. The MDLs indicates the superior sensitivity of ICP-MS to determinate heavy metal migration in food simulant. ❑ Results and Discussion Calibration Linearity Under the experimental conditions described in the section above, good linearity of calibration curves was achieved. The correlation coefficients are shown in Table 2 with r >0.9999 for targeted elements. LODs and LOQs were calculated based on 3 and 10 times the standard deviations of 10 continuous measurement of the calibration blank. Sub ppb or ppt level of LODs and LOQs were achieved for all analytes especially for the potentially toxic elements such as As, Cd and Pb. Recovery and Repeatability The ICPMS method was evaluated by spiking a known concentration (10 ppb) of heavy metals into food simulant B soaked with two plastic packages samples (PS container and PP container). The spike recovery rates achieved were between 87% to 116% for 14 heavy metals as shown in Table 3. Good recovery rates indicated the method accuracy and absence of interference. The repeatability for three replicates were checked with RSD% obtained less than 3% for most of the elements as shown in Table 3.
Application News No. AD-0207 Element PS Recovery PS RSD% PP Recovery PP RSD% Al 27 114% 3.3 116% 2.1 As 75 108% 1.9 111% 1.5 Ba 138 99% 2.1 95% 3.7 Cd 112 102% 1.5 98% 2.6 Co 59 106% 2.2 105% 1.2 Cr 53 102% 1.3 101% 0.6 Cu 65 111% 2.5 112% 1.8 Fe 57 101% 3.9 100% 2.0 Li 7 87% 2.2 87% 0.2 Mn 55 101% 1.8 102% 1.5 Ni 62 102% 3.1 101% 0.5 Pb 208 98% 2.0 101% 0.9 Sb 123 112% 1.0 114% 1.7 Zn 68 103% 2.2 109% 2.0 Table 3: Spike recovery rates and RSD% (n=3) from food simulant B for PS container and PP container Element PS container (μg/kg) PP container (μg/kg) PE film (μg/kg) MDL (μg/kg) Al 49.3 71.4 135.5 2.01 As 0.11 0.06 0.48 0.05 Ba 14.0 7.14 22.9 0.05 Cd N.D. N.D. 0.26 0.012 Co N.D. N.D. N.D. 0.006 Cr 6.50 0.15 0.84 0.13 Cu 30.4 19.6 13.3 1.23 Fe 17.0 2.39 142.5 1.04 Li N.D. N.D. N.D. 0.64 Mn 2.51 N.D. 52.8 0.08 Ni 8.81 1.86 2.14 0.67 Pb 2.22 0.19 3.27 0.06 Sb 0.08 0.04 0.40 0.006 Zn 34.60 23.50 685.5 0.73 Table 4: Heavy metal migration into food simulant B for different plastic packaging materials and MDLs Element Food Simulant A DI water 2% HNO3 Food Simulant B (3% Acetic acid) Al 21.0 29.9 135.5 As 0.01 0.15 0.48 Ba 13.4 15.8 22.9 Cd N.D. 0.05 0.26 Co N.D. N.D. N.D. Cr 0.03 0.69 0.84 Cu 1.94 3.86 13.3 Fe 3.72 73.0 142.5 Li N.D. N.D. N.D. Mn 1.09 15.9 52.8 Ni 0.91 1.37 2.14 Pb 0.02 2.54 3.27 Sb 0.04 0.08 0.40 Zn 31.4 127.5 685.5 Table 5: Comparison of heavy metal migration from PE film into different aqueous solutions. (unit in μg/kg)
Application News The effect of contact time on migration of heavy metal were also evaluated for PS container and PE film using food simulant B. The results with different contact time (1h vs 72h) were compared and shown in Figure 2. For both plastic packaging materials, the migration of heavy metals increased significantly with extended contacting time, indicating that the contact time is an important factor for element migration evaluation. No. AD-0207 www.shimadzu.com/an/ Shimadzu Corporation SHIMADZU (Asia Pacific) Pte. Ltd 79 Science Park Drive, #02-01/08 Cintech IV, Singapore 118264, www.shimadzu.com.sg ; Tel: +65-6778 6280 Fax: +65-6778 2050 For Research Use Only. Not for use in diagnostic procedures. Contents and/or instrumentations in this application may not available in some countries under each regulation. Please contact the local representatives in details. Copyright © 2019 SHIMADZU (Asia Pacific) Pte. Ltd. All rights reserved. No part of this document may be reproduced in any form or by any means without permission in writing from SHIMADZU (Asia Pacific) Pte. Ltd. Effects of food simulant type and contact time on heavy metal migration Table 5 shows that heavy metal leaching was more significant from plastic materials exposed to the food simulant B as compared to DI water and 2% HNO 3 . Note that simulant B is the acidic mimic food used mostly in heavy metal migration test and investigation. The solution of 2% nitric acid is to mimic acidic conditions of some preserved food. ❑ Conclusions ❑ References In the present work, we have studied the heavy metal migration from three different plastic materials used for food packaging with a developed ICP-MS method. The leaching amounts of 14 metallic elements from different plastics varied largely when 3% acetic acid was used as food simulant. Toxic elements such as As, Cd and Pb were detected in the leachate but in low levels. Significantly more heavy metal leaching into food simulant B than other aqueous solutions was observed. Obvious more metal migration was found with increasing contact time from 1h to 72h. The results showed good spike recovery rates and low RSD% for repeated measurements demonstrating the accuracy and precision of the determinations. 1. Zhanhua Dong, Lixin Lu, Zhigang Liu, Yali Tang, and Jun Wang, “Migration of Toxic Metals from Ceramic Food Packaging Materials into Acid Food Simulants,” Mathematical Problems in Engineering, vol. 2014, Article ID 759018 7 pages, 2014. 2. COMMISSION REGULATION (EU) No 1935/2004 & No 10/2011 on plastic materials and articles intended to come into contact with food (OJ L 12, 15.1.2011, p. 1) Figure 2: Effect of contact time (1h vs 72h) on heavy metal migration into food simulant B for PS container and PE film.
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