Evaluation of some screening methods for the analysis of contaminants in recycled polyethylene terephthalate flakes.

A range of different analytical techniques were used to test recycled polyethylene terephthalate (PET) flakes for potential chemical contaminants. The techniques used were headspace gas chromatography coupled to mass spectrometry (GC-MS), liquid extraction followed by GC-MS, supercritical-fluid extraction followed by GC-MS, and migration testing followed by elemental analysis using inductively coupled plasma mass spectroscopy (ICP-MS). The PET samples were 50 representative samples taken from 600 that had been collected throughout Europe and which had been screened for potential contaminants using a single technique of high-temperature GC-MS. Six of the 50 samples tested had been spiked with a selection of model contaminants, three samples were virgin PET flakes and two of the samples were from supercleaning processes. All samples were analysed 'blind' in this exercise. The qualitative results showed that most of the contaminants came from the first use, being flavour-aroma compounds from soft drinks. The quantitative analysis found concentrations under a few mg kg(-1) in the polymer, except for the spiked samples. Element migrations were low and only calcium, silicon and sodium had median migrations above 50 microg l(-1). This in-depth analysis of recycled PET flakes did not identify any significant contaminants that had not already been detected by the high-temperature static GC-MS screening method, thus demonstrating its utility.

Determination of bisphenol-type contaminants from food packaging materials in aqueous foods by solid-phase microextraction-high-performance liquid chromatography.

A fast screening method consisting of off-line solid-phase microextraction coupled to HPLC and fluorescence detection, suitable for the analysis of several bisphenol derivatives and their degradation products in aqueous solution, has been developed. Detection limits of 0.7 ng ml(-1) for 2,2-bis[4-(glycidyloxy)phenyl]propane, 0.9 ng ml(-1) for bisphenol A bis(3-chloro-2-hydroxypropyl)ether, 1.1 ng ml(-1) for 2,2-bis(4-hydroxyphenyl)propane and 2.4 ng ml(-1) for bisphenol F diglycidyl ether have been achieved working in the linear range 10-500 ng ml(-1). The good analytical features achieved make the proposed method an interesting option for the direct determination of these compounds in aqueous canned food such as peas, tuna, olives, maize, artichokes or palm hearts. Both the optimization process and the results, including the analysis of real samples, are given and discussed.

Verification of the findings of acrylamide in heated foods.

We report here the first confirmation of the recent Swedish findings of acrylamide in heated foods. The verification exercise used an LC-MS/MS method developed for the purpose as well as an established GCMS method for acrylamide analysis. LC-MS/MS was suitable for the direct determination of acrylamide in aqueous extracts of foods by isotope dilution mass spectrometry (IDMS) using triply deuterated acrylamide. Some food matrices were not suited to the new method and mixed-mode solid-phase extraction (SPE) was used to clean these extracts. The foods tested included UK versions of some of the key food groups analysed in Sweden. Also tested were some foods heated under home-cooking conditions. There was good agreement between the LC-MS/MS results and the GC-MS results and the levels of acrylamide found here were similar to those reported for the corresponding foods analysed in the Swedish study. The analyses confirmed that acrylamide is absent from the raw or boiled foods but present at significant levels in fried, grilled, baked and toasted foods. The highest result was 12000 microg kg(-1) acrylamide in overcooked oil-fried chips.

Measurement of styrene oxide in polystyrenes, estimation of migration to foods, and reaction kinetics and products in food simulants.

The concentration of styrene-7,8-oxide has been measured in nine base resins and 16 samples of polystyrene articles intended for food contact. The epoxide was not detected in the resins (limit of detection 0.5 mg/kg) but was found in 11 of the 16 packaging samples at up to 2.9 mg/kg. Assuming that the propensity of styrene oxide to migrate is the same as styrene monomer, and using existing survey data for styrene monomer in packaging and foods, the migration levels expected for styrene oxide were calculated. Estimates were from 0.002 to 0.15 microgram/kg styrene oxide in foods. The stability of styrene oxide in the four standard EU food simulants was studied at 40, 100, 150 and 175 degrees C, to establish the transformation products to be expected following migration testing. The half-life at 40 degrees C in distilled water, 15% aqueous ethanol, 3% aqueous acetic acid and olive oil was 15, 23, < 1, > 2000 hr, respectively. The principal product was the diol from hydrolysis of the epoxide group. Ring opening in aqueous ethanol simulant gave the diol and also the glycol monoethyl ether. It is concluded that this instability of styrene oxide will reduce concentrations in foods, from an already low migration level to even lower levels with the formation of hydrolysis products that are less toxic than the parent epoxide.

Reactions of epoxide monomers in food simulants used to test plastics for migration.

The reactions of four epoxides used as monomers for food contact plastics were studied in the food simulants distilled water, 15% aqueous ethanol, 3% aqueous acetic acid and olive oil. Loss of the parent substance and formation of products was monitored to establish the transformation products to be expected in each simulant following migration testing of plastics. Each epoxide was stable in olive oil but suffered extensive loss in the three aqueous simulants. Reaction half-lives were from < 1 to 10 h in aqueous acetic acid, 25-63 h in distilled water, and 33-87 h in aqueous ethanol simulant. Hydrolysis to the diol was the main reaction pathway. Epoxide ring opening in aqueous ethanol simulant gave the diol and also the diol monoethyl ether. It is concluded that, for aqueous simulants and by implication for most foods, testing plastics against specific migration limits for epoxides is not likely to give reliable results due to their reactivity. The present EC mode of control for these reactive monomers, via compositional limits in food contact plastics, is more practical since the hydrolysis products are less toxic than the parent epoxide.

Practical aspects of testing food contact materials for migration.

Progress in three areas has provided analytical methods and understanding to assist in migration testing for compliance with European Community Directives on food contact materials. A simple migration test has been developed to indicate whether or not a food makes fatty contact with plastics. This test is then used to guide the initial choice of appropriate food simulants. The Karl Fischer technique for water determination has been used to eliminate the need to humidity condition plastics in overall migration testing. This results in more rapid and more reliable migration testing. Finally, the stability of 'positive-list' monomers and other starting substances has been examined in food simulants. This identifies those substances which, for reasons of reactivity, may not be expected to survive a migration test and for which, therefore, migration testing as such is inappropriate.

Gas chromatographic/mass spectrometric determination of benzene in nonstick cookware and microwave susceptors and its migration into foods on cooking.

Benzene in poly(tetrafluoroethylene) (PTFE) coatings of nonstick cookware was determined by heating a small amount of coating in a sealed vial. Gas chromatography/mass spectrometry (GC/MS) was used to analyze the vial headspace for benzene. A small survey (26 samples) of retail nonstick cookware detected benzene ranging from 2 to 50 micrograms/dm2 in 7 samples. Nonstick frying pans with various polymer coatings were obtained directly from 1 manufacturer. Benzene (6-30 micrograms/dm2) was detected in a number of these samples and was attributed to the use of a phenylmethyl silicone ingredient that contained benzene at 360 mg/kg. To determine the possible transfer of benzene from these coatings during normal use, several foods (puddings, cakes, and roast potatoes) were prepared in previously unused cookware. The foods were analyzed by using static headspace GC/MS. Benzene was not detected in any of these foods at a limit of detection of 2 micrograms/kg. In related studies, the determination of benzene release from microwave susceptors was performed by heating the materials in a sealed system at 190 degrees C for 4 min. Benzene release above 1 microgram/dm2 was not detected in 24 samples of susceptors. However, 1 specially supplied sample of non-metallized susceptor released 10 micrograms/dm2 benzene when heated above normal anticipated temperatures of usage (to 220 degrees C). Foods such as french fries and pizza when cooked according to the manufacturer's instructions in susceptors contained no benzene with a limit of detection of 2 micrograms/kg. Even under abuse conditions of susceptors, the transfer of benzene to foods remained below this limit.