Migration of formaldehyde and melamine from melaware and other amino resin tableware in real life service

ABSTRACT

The migration of formaldehyde and melamine monomers has been measured on 90 samples of plastic tableware in three different situations – new articles, already used articles and artificially aged articles – by using simulant, contact times and temperatures prescribed by Commission Regulation (EU) No. 10/2011. Formaldehyde was determined by ultraviolet spectroscopy analysis of the coloured complex obtained by reaction with chromotropic acid. Melamine was measured by an ultra high performance liquid chromatography method. Fourier Transformed – Infrared Analysis was applied to characterise the plastic. The results highlighted the presence of different amino resins based on formaldehyde-melamine, urea-formaldehyde or melamine-urea-formaldehyde with different migration behaviour. The migration of monomers was related to progressive degradation of the resins. Ageing studies demonstrated that the potential degradation of the resins and the consequent migration of the monomers may continue throughout the service life of the product. The specific migration limit (SML) of melamine was exceeded after ageing.     

Migration of formaldehyde and melamine monomers from kitchen- and tableware made of melamine plastic

Migration of one or both formaldehyde and/or melamine monomers was found in seven of ten tested melamine samples bought on the Danish market. The samples were a bowl, a jug, a mug, a ladle, and different cups and plates. No violation of the European Union-specific migration limits for melamine (30 mg kg^-1) and formaldehyde (15 mg kg^-1) was found after three successive exposures to the food stimulant 3% acetic acid after 2 h at 70°C. To investigate the effects of long-term use, migration tests were performed with two types of cups from a day nursery. Furthermore, medium-term use was studied by ten successive exposures of a plate to 3% acetic acid for 30 min at 95°C. The results indicate that continuous migration of formaldehyde and melamine takes place during the lifetime of these articles. The molar ratio of released formaldehyde to melamine was seen to decrease from 12 to about 5. This indicates that, first, the migration of residual monomers is most important, but in the long-term, breakdown of the polymer dominates. Two CEN methods were used to determine the concentration of monomers: a spectrophotometric method for formaldehyde and a UV-HPLC method for melamine.     

Migration of formaldehyde from melamine-ware: UK 2008 survey results

Fifty melamine-ware articles were tested for the migration of formaldehyde – with hexamethylenetetramine (HMTA) expressed as formaldehyde – to see whether the total specific migration limit (SML(T)) was being observed. The SML(T), given in European Commission Directive 2002/72/EC as amended, is 15 mg kg^?1. Fourier transform-infrared (FT-IR) spectroscopy was carried out on the articles to confirm the plastic type. Articles were exposed to the food simulant 3% (w/v) aqueous acetic acid under conditions representing their worst foreseeable use. Formaldehyde and HMTA in food simulants were determined by a spectrophotometric derivatization procedure. Positive samples were confirmed by a second spectrophotometric procedure using an alternative derivatization agent. As all products purchased were intended for repeat use, three sequential exposures to the simulant were carried out. Formaldehyde was detected in the simulant exposed to 43 samples. Most of the levels found were well below the limits set in law such that 84% of the samples tested were compliant. However, eight samples had formaldehyde levels that were clearly above the legal maximum at six to 65 times the SML(T).     

Analysis of melamine migration from melamine food contact articles

Migration of melamine has been determined for 41 types of retail melamine-ware products in Malaysia. This study was initiated by the Ministry of Health, Malaysia, in the midst of public anxiety on the possibility of melamine leaching into foods that come into contact with the melamine-ware. Thus, the objective of this study was to investigate the level of melamine migration in melamine utensils available on the market. Samples of melamine tableware, including cups and plates, forks and spoons, tumblers, bowls, etc., were collected from various retail outlets. Following the test guidelines for melamine migration set by the European Committee for Standardisation (CEN 2004) with some modifications, the samples were exposed to two types of food simulants (3% acetic acid and distilled water) at three test conditions (25°C (room temperature), 70 and 100°C) for 30 min. Melamine analysis was carried out using LC–MS/MS with a HILIC column and mobile phase consisting of ammonium acetate/formic acid (0.05%) in water and ammonium acetate/formic acid (0.05%) in acetonitrile (95?:?5, v/v). The limit of quantification (LOQ) was 5?ng/ml. Melamine migration was detected from all samples. For the articles tested with distilled water, melamine migration were [median (interquartile range)] 22.2 (32.6), 49.3 (50.9), 84.9 (89.9) ng/ml at room temperature (25°C), 70 and 100°C, respectively. In 3% acetic acid, melamine migration was 31.5 (35.7), 81.5 (76.2), 122.0 (126.7) ng/ml at room temperature (25°C), 70 and 100°C, respectively. This study suggests that excessive heat and acidity may directly affect melamine migration from melamine-ware products. However the results showed that melamine migration in the tested items were well below the specific migration limit (SML) of 30?mg/kg (30,000?ng/ml) set out in European Commission Directive 2002/72/EC.     

网购密胺餐具的质量分析

目的 测定和分析网购密胺餐具的材质、高锰酸钾消耗量和脱色,研究迁移温度对甲醛迁移量的影响,评估网购密胺餐具的质量。方法 采集网上在售的18批次密胺餐具,通过衰变全反射（Attenuated Total Reflection） 红外法分析密胺餐具和脲醛餐具的特征吸收峰,快速区别密胺餐具和脲醛餐具。依据GB 4806.7-2016《食品安全国家标准 食品接触用塑料材料及制品》对密胺餐具高锰酸钾消耗量、脱色进行了测定和分析。依据GB 4806.6-2016 《食品安全国家标准 食品接触用塑料树脂》对密胺餐具的甲醛迁移量进行测定和分析。结果 脲醛餐具占样品总数44.4%,覆盖密胺涂层的脲醛餐具占样品总数33.3%;11.1%的样品高锰酸钾消耗量不合格;11.1%的样品4%乙酸浸泡液脱色不合格;11.1%的样品甲醛迁移量不合格（4%乙酸,70℃,2h）。结论 本次网上购买的密胺餐具高锰酸钾消耗量、脱色存在不符合GB 4806.7-2016的现象;甲醛迁移量不符合GB 4806.6-2016标准的现象,存在用脲醛餐具替代密胺餐具或是在脲醛餐具上覆盖密胺涂层以次充好的现象。     

Comparison of the migration of melamine from melamine-formaldehyde plastics ('melaware') into various food simulants and foods themselves

A variety of melaware articles were tested for the migration of melamine into the food simulant 3% w/v acetic acid as a benchmark, and into other food simulants, beverages and foods for comparison. The results indicate that the acidity of the food simulant plays a role in promoting migration, but not by as much as might have been anticipated, since 3% acetic acid gave migration values about double those obtained using water under the same time and temperature test conditions. In contrast, migration into the fatty food simulant olive oil was not detectable and at least 20-fold lower than with the aqueous food simulants. This was expected given the solubility properties of melamine and the characteristics of the melaware plastic. Migration levels into hot acidic beverages (apple juice, tomato juice, red-fruit tea and black coffee) were rather similar to the acetic acid simulant when the same time and temperature test conditions are used, e.g. 2 h at 70°C. However, migration levels into foods that were placed hot into melaware articles and then allowed to cool on standing were much lower (6-14 times lower) than if pre-heated food was placed into the articles and then maintained (artificially) at that high temperature in the same way that a controlled time-temperature test using simulants would be conducted. This very strong influence of time and especially temperature was manifest in the effects seen of microwave heating of food or beverage in the melaware articles. Here, despite the short duration of hot contact, migration levels were similar to simulants used for longer periods, e.g. 70°C for 2 h. This is rationalized in terms of the peak temperature achieved on microwave heating, which may exceed 70°C, counterbalancing the shorter time period held hot. There was also evidence that when using melaware utensils in boiling liquids, as for stovetop use of spatulas, the boiling action of circulating food/simulant can have an additional effect in promoting surface erosion, increasing the plastic decomposition and so elevating the melamine release.     

An attempt to estimate service terms of tableware made of amino resins

This study presents a first attempt to estimate the service terms of food contact articles made of melamine/formaldehyde and urea/formaldehyde plastics. This was achieved by following the continuous release of formaldehyde into food simulants throughout the use phase until the levels of formaldehyde migration exceeded the specific migration limit (SML), or samples were damaged and not suitable for further tests. Two test conditions were established to follow customary practices as much as possible: scenario 1, successive washing; and scenario 2, alternate courses of exposure and washing. Real melamine tableware showed conformity to the SML of formaldehyde over the course of 1500 successive washings; the estimated service term was 750 days, or about 2 years. Moreover, this service term agreed well with that found in real practice. When washing urea/formaldehyde tableware with sponges, the levels of formaldehyde migration remained below the SML, but samples eventually fractured. In the case of scrubbing pads, the levels of formaldehyde migration constantly increased and ultimately exceeded the SML. Scenario 2 resulted in accelerated migration of formaldehyde, and the SML was exceeded more rapidly than in scenario 1. Because surface roughening occurred during customary use and also during washing with scrubbing pads, it was necessary to adopt reduction factors to take into account the effects of handling when calculating service terms of articles. The results showed reduction factors ranging from 1 to 3, depending on test conditions (scenario 1 or 2) and anticipated use conditions (hot fill or use at ambient temperature). Thus, the estimated service terms of urea formaldehyde products were 117 and 175 days under hot fill and ambient conditions, respectively. These results corresponded with service terms observed in real practice, which were reported to be in the ranges of 3–4 and 6–7 months, respectively. Taking into account the time and expenses consumed during experiments, scenario 1 (successive washing with scrubbing pads) would be recommended as an appropriate method for following the migration of formaldehyde over repeated use phases and for estimating the service terms of amino-resin-based articles for food contact use.     

Comparison of the migration of melamine from melamine–formaldehyde plastics (‘melaware’) into various food simulants and foods themselves

A variety of melaware articles were tested for the migration of melamine into the food simulant 3% w/v acetic acid as a benchmark, and into other food simulants, beverages and foods for comparison. The results indicate that the acidity of the food simulant plays a role in promoting migration, but not by as much as might have been anticipated, since 3% acetic acid gave migration values about double those obtained using water under the same time and temperature test conditions. In contrast, migration into the fatty food simulant olive oil was not detectable and at least 20-fold lower than with the aqueous food simulants. This was expected given the solubility properties of melamine and the characteristics of the melaware plastic. Migration levels into hot acidic beverages (apple juice, tomato juice, red-fruit tea and black coffee) were rather similar to the acetic acid simulant when the same time and temperature test conditions are used, e.g. 2?h at 70°C. However, migration levels into foods that were placed hot into melaware articles and then allowed to cool on standing were much lower (6–14 times lower) than if pre-heated food was placed into the articles and then maintained (artificially) at that high temperature in the same way that a controlled time–temperature test using simulants would be conducted. This very strong influence of time and especially temperature was manifest in the effects seen of microwave heating of food or beverage in the melaware articles. Here, despite the short duration of hot contact, migration levels were similar to simulants used for longer periods, e.g. 70°C for 2?h. This is rationalized in terms of the peak temperature achieved on microwave heating, which may exceed 70°C, counterbalancing the shorter time period held hot. There was also evidence that when using melaware utensils in boiling liquids, as for stovetop use of spatulas, the boiling action of circulating food/simulant can have an additional effect in promoting surface erosion, increasing the plastic decomposition and so elevating the melamine release.     

Survey of counterfeit melamine tableware available on the market in Thailand,and its migration

A simple measurement of sample density by adopting the principles of buoyancy could help screen counterfeit melamine ware if the density was below 1.50?g?cm^?3. However, samples with a density exceeding 1.50?g?cm^?3 were not necessarily made from melamine formaldehyde. FTIR analysis showed that all counterfeit products were made of urea formaldehyde and coated on the food-contact side with melamine formaldehyde, a tactic probably intended to cover up the true product features. The overall migration of real and counterfeit melamine samples complied with both European Union and Thai regulations, as the exposure layers in both cases were melamine formaldehyde. Formaldehyde migration failed to comply with Thai standards, but this was not the case for European Union standards. However, the results showed a significant inconsistency between individual items of the same brand and between individual exposures of the same test specimen. This indicated the inherent inhomogeneity between individual items, which mainly resulted from the manufacturing process: for instance, insufficient temperature and time to obtain complete polycondensation of monomers. Therefore, it is recommended that constant surveillance be conducted on melamine articles available in the marketplace in terms of quality and safety.     

Migration of trimellitic acid from epoxy anhydride can coatings into foods

The migration of trimellitic acid and its esters from epoxy anhydride coatings was determined in simulants as well as in canned foods. The most appropriate simulant was a combination of EC simulants B and C: 2% acetic acid/10% ethanol in water. The average migration into food was 900 μg kg^-1. This far exceeds the 50 μg kg^-1 for which the safety of trimellitic acid and its anhydride is ensured and the Swiss legal limit (QM(T) of 5 mg kg^-1 coating). Furthermore, much trimellitic acid migrated as (unidentified) esters, i.e. toxicological testing of free trimellitic acid is inadequate for the material that in reality migrates.     

Effects of microwave heating on the migration of substances from melamine formaldehyde tableware

Melamine formaldehyde (MF) tableware, after undergoing repeated heating in a microwave oven for 1, 2, 3 or 5 min, was tested for migration into 3% (w/v) acetic acid, a food simulant. Overall migration (OM) consistently increased with an increasing number of heating/washing cycles, while formaldehyde was found at low concentrations or was not detectable. Unexpectedly, the 1-min series caused the most rapid increase in OM; the European Union regulatory limit of 10 mg dm^–2 was exceeded after 25 cycles. The number of cycles required to reach the OM limit rose to 29 and 67 for the 2- and 3-min series, respectively. Only 37 cycles were needed in the case of the 5-min series; however, the cumulative exposure time to microwave irradiation was relatively close to that of the 3-min series. These findings indicate that microwave heating affects the migration of MF in a significantly different manner as compared with conventional heating reported in previous studies. Fourier transform infrared spectroscopy (FTIR) spectra of MF after completing the microwave heating series show that the plastic was not fully cured, as evidenced by the absence of methylene linkages. The majority of migrants obtained from OM tests consisted of low molecular weight methylol melamine derivatives. The results indicate that microwave heating allowed demethylolation, addition and condensation reactions to occur, which was not the case when using conventional heating. This study demonstrates that microwave heating for 1–2 min in a repeated manner is of high concern in terms of consumer health. It was found that the service terms of melamine ware under microwave heating were drastically reduced, by more than 10-fold, as compared with the service terms under conventional heating. Hence, it is strongly recommended that manufacturers of MF articles provide instructions for use, e.g. “Do not use in microwave”, which should be clearly visible to consumers and not easily detachable.     

学校食堂在用密胺和不锈钢餐具检测及风险分析

目的 通过对学校食堂在用密胺和不锈钢餐具进行检测分析,并参照相关国际标准与国家标准对检测结果进行分析,以评估学校食堂在用密胺和不锈钢餐具的风险状况,为建立风险防范措施及优化现行标准提供理论依据。方法 本次检测通过对密胺餐具中甲醛迁移量、三聚氰胺迁移量;对不锈钢餐具中铅迁移量、砷迁移量、镉迁移量和镍迁移量六项指标,对食堂抽取的100批次密胺在用餐具和100批次不锈钢在用餐具样品进行风险分析。结果 本次研究共发现在用问题餐具共72批次,占比36.0%。其中在用问题密胺餐具55批次,占密胺餐具总量的55.0%;问题不锈钢餐具17批次,占不锈钢餐具总量的17.0%。密胺餐具不合格项目主要为甲醛和三聚氰胺(4%乙酸,水)的迁移量超标,不锈钢餐具不合格项目主要为铅、镉元素的迁移量超标。结论 食堂应制定密胺餐具相应的使用管理规范,设定密胺餐具的使用年限为1年以内,同时规范餐具的消毒、清洗等操作,从而有效地降低甲醛和三聚氰胺的迁移风险;应加强不锈钢餐具原料供应链管理,从源头降低风险。     

Migration and sensory properties of plastics-based nets used as food-contacting materials under ambient and high temperature heating conditions

Overall migration from a wide range of commercial plastics-based netting materials destined to be used as either meat or vegetable packaging materials into the fatty food simulant isooctane or the aqueous simulant distilled water, respectively, was studied. In addition, sensory tests of representative netting materials were carried out in bottled water in order to investigate possible development of off-odour/taste and discoloration in this food simulant as a result of migration from the netting material. Sensory tests were supplemented by determination of the volatile compounds' profile in table water exposed to the netting materials using SPME-GC/MS. Test conditions for packaging material/food simulant contact and method of overall migration analysis were according to European Union Directives 90/128 (EEC, 1990) and 2002/72 (EEC, 2002). The results showed that for both PET and polyethylene-based netting materials, overall migration values into distilled water ranged between 11.5 and 48.5 mg l^-1, well below the upper limit (60 mg l^-1) for overall migration values from plastics-packaging materials set by the European Union. The overall migration values from netting materials into isooctane ranged between 38.0 and 624.0 mg l^-1, both below and above the European Union upper limit for migration. Sensory tests involving contact of representative samples with table water under refluxing (100°C/4 h) conditions showed a number of the netting materials produced both off-odour and/or taste as well as discoloration of the food simulant rendering such materials unfit for the packaging of foodstuffs in applications involving heating at elevated temperatures. GC/MS analysis showed the presence of numerous volatile compounds being produced after netting materials/water contact under refluxing conditions. Although it is extremely difficult to establish a clear correlation between sensory off-odour development and GC/MS volatile compounds' profile, it may be postulated that plastics oxidation products such as hexanal, heptanal, octanal and 2,6 di-tert-butylquinone may contribute to off-odour development using commercially bottled table water as a food simulant. Likewise, compounds such as carbon disulfide, [1,1'-biphenyl]-2-ol and propanoic acid, 2 methyl 1-(1,1-dimethyl)-2-methyl-1,3-propanediyl ester probably originating from cotton and rubber components of netting materials may also contribute to off-odour/taste development.     

Migration of 2-butoxyethyl acetate from polycarbonate infant feeding bottles

An enforcement campaign was carried out to assess the migration of 2-butoxyethyl acetate (2-BEA) from polycarbonate infant feeding bottles intended for repeated use. Migration was measured by three successive migration tests into two of the European Union official food simulants: distilled water and 3% acetic acid testing at 40°C for 10 days. The Danish Veterinary and Food Administration (DVFA) has assessed that a migration above 0.33 mg for 2-BEA and a group of eight related substances kg^-1 foodstuff from plastics articles used exclusively for infants is unacceptable. Migration of 2-BEA was found from eight of 12 bottles. However, migration above the target value of 0.33 mg kg^-1 was not observed in the third decisive test from any of the 12 different brands of polycarbonate feeding bottles. A migration of between 0.05 and 0.26 mg kg^-1 from seven of 12 bottles was measured to 3% acetic acid in the third test, whereas no migration to distilled water was observed in the third test. The average recovery of 2-BEA after the 10-day exposure at the target value of 0.33 mg kg^-1 was 77% into distilled water and 36% into 3% acetic acid. The limited recovery was understandable as 2-BEA was partly hydrolysed in the aqueous food simulants and 2-butoxyethanol, a hydrolysis product and one of the related substances was identified. Quantification was carried out using gas chromatography after liquid/liquid extraction of the food simulant.     

Migration of melamine from can coatings cross-linked with melamine-based resins,into food simulants and foods

Resins based on melamine-formaldehyde and related analogues such as methylolated melamine are used to cross-link coatings used inside food cans and on the metal closures of glass jars. Thirteen commercially coated cans and closures representing 80% of the European market were tested using simulants under realistic industrial heat-processing conditions for canned and jarred foods. The food simulants and the retort conditions used were 3% acetic acid for 1?h at 100°C and 10% ethanol for 1?h at 130°C. The highest migration level seen for melamine into simulant was 332?µg?kg^?1. There was no detectable migration of the melamine analogues cyanuric acid (<1?µg?kg^?1) or ammelide (<5?µg?kg^?1) from any sample. Twelve of the thirteen samples released no detectable ammeline (<5?µg?kg^?1) but the coating giving the highest release of melamine did also release ammeline at 8?µg?kg^?1 with the higher of the two process temperatures used. Migration experiments into food simulant and foods themselves were then conducted using two experimental coatings made using amino-based cross-linking resins. Coated metal panels were exposed to the food simulant 10% (v/v) aqueous ethanol and to three foodstuffs under a range of time and temperature conditions both in the laboratory and in a commercial food canning facility using proprietary time and temperature conditions. The highest migration into a food was 152?µg?kg^?1 from the first coating processed for a long time at a moderate sterilisation temperature. The highest migration into simulant was also from this coating at 220?µg?kg^?1 when processed at 134°C for 60?min, dropping to 190?µg?kg^?1 when processed at 123°C for 70?min. Migration from the second coating was quite uniformly two to three times lower under all tests. These migration results were significantly higher than the levels of melamine extractable using 95% ethanol at room temperature. The experiments show that commercial canning and retorting can be mimicked in an acceptable way using laboratory tests with an autoclave or a simple pressure cooker. The results overall show there is hydrolytic degradation of the melamine cross-linked resins to release additional melamine. There is a strong influence of the temperature of heat treatment applied with foods or simulants but only a minor influence of time of heating and only a minor influence, if any, of food/simulant acidity.     

密胺餐具的鉴别及其三聚氰胺和甲醛迁移风险调查

目的对密胺餐具中三聚氰胺和甲醛迁移量进行调查研究,并对数据进行分析。方法在上海的企业和消费市场采集密胺餐具共40份,采用红外光谱法进行材料鉴别,依照GB 4806.7—2016《食品安全国家标准食品接触用塑料材料及制品》和GB 31604.1—2015《食品安全国家标准食品接触材料及制品迁移试验通则》进行迁移试验,测定三聚氰胺和甲醛迁移量。结果密胺餐具存在材质未标识、标识不清或标识有误的现象;脲醛树脂中三聚氰胺和甲醛的迁移量均高于密胺树脂,且迁出量与温度呈正相关。结论脲醛树脂应用于餐具存在风险,国家标准中有必要增加密胺材质鉴定检测方法。     

Survey of counterfeit melamine tableware available on the market in Thailand, and its migration

A simple measurement of sample density by adopting the principles of buoyancy could help screen counterfeit melamine ware if the density was below 1.50 g cm?3. However, samples with a density exceeding 1.50 g cm?3 were not necessarily made from melamine formaldehyde. FTIR analysis showed that all counterfeit products were made of urea formaldehyde and coated on the food-contact side with melamine formaldehyde, a tactic probably intended to cover up the true product features. The overall migration of real and counterfeit melamine samples complied with both European Union and Thai regulations, as the exposure layers in both cases were melamine formaldehyde. Formaldehyde migration failed to comply with Thai standards, but this was not the case for European Union standards. However, the results showed a significant inconsistency between individual items of the same brand and between individual exposures of the same test specimen. This indicated the inherent inhomogeneity between individual items, which mainly resulted from the manufacturing process: for instance, insufficient temperature and time to obtain complete polycondensation of monomers. Therefore, it is recommended that constant surveillance be conducted on melamine articles available in the marketplace in terms of quality and safety.     

蜜胺餐具中三聚氰胺单体的迁移规律研究

结合蜜胺餐具的实际使用情况,选用合适的食品模拟物进行迁移实验,采用LC-MS/MS法测定三聚氰胺迁移量,研究蜜胺餐具中三聚氰胺单体的迁移规律。重点考察了食品模拟物种类、接触时间、接触温度、乙酸浓度、乙醇浓度、重复使用和微波加热等迁移条件下蜜胺餐具中三聚氰胺迁移量的变化情况。结果表明酸性食品和牛奶中的三聚氰胺迁移风险较高,且需控制蜜胺餐具的使用温度、盛放时间、重复使用次数及微波加热功率和时间以降低密胺餐具中三聚氰胺迁移风险。     

食品包装用三聚氰胺成型品中甲醛迁移规律的研究

目的研究食品包装三聚氰胺成型品中甲醛迁移规律。方法采用盐酸苯肼分光光度法测定60、75和90℃三个模拟温度下甲醛从食品包装用三聚氰胺成型品中迁移至3%乙酸、15%乙醇两种模拟溶剂中的量。根据所得的实验数据,讨论了不同温度和不同食品模拟物的选择对甲醛迁移行为的影响,以及样本重复10次进行迁移实验时甲醛迁移量的变化规律。结果3%醋酸作为模拟溶剂的甲醛迁移量较15%乙醇作为模拟溶剂的高,且其迁移量随着模拟温度的升高而增多;3个温度下,2种模拟溶剂中单次迁移实验的甲醛迁移量均未超过我国国家标准的限量值和欧盟规定对其规定的特定迁移量(SML)2.5 mg.dm-2,而以3%醋酸作为模拟溶剂的甲醛的10次迁移实验的总量均超过欧盟对甲醛的特定迁移量。结论食品包装用三聚氰胺成型品不宜在酸性和高温条件下使用。     

Migration of styrene monomer, dimers and trimers from polystyrene to food simulants

Migration experiments with polystyrene were performed in two-sided contact with n-heptane and distilled water as the food simulants at temperatures of 10, 24 and 40, and 40, 60 and 90°C, respectively. The surface/volume ratios in the migration cell were set at 8.04 and 10.05 dm² l^-1 for n-heptane and distilled water, respectively. Styrene monomer, styrene dimers and styrene trimers migrating to the food simulants were determined by GC-FID analysis. Heptane fully extracted the styrene monomer and the oligomers from the polystyrene sheet, whereas in the distilled water only the migrated styrene trimers could be detected. To determine the apparent diffusion coefficient, the migration process was analysed based on Fick's law. The higher the molecular weight of the oligomers, the more significant the reduction in the diffusion coefficient. Higher molecular weight oligomers also had lower activation energy of diffusion when the temperature dependence of diffusivity was analysed by the Arrhenius equation. The diffusion coefficient of the trimers was much higher for heptane contact than for water. The activation energy of the diffusion of trimers for water contact was higher than that for heptane.