John W. Gramshaw

Element residues in food contact plastics and their migration into food simulants, measured by inductively-coupled plasma-mass spectrometry

Polymers intended for food contact use have been analysed for inorganic residues which can be attributed to a range of substances employed as polymerization aids (e.g. catalysts), or to additives incorporated into the polymer to fulfil a specific task (e.g. lubricants). The migration of these residues into food simulants was studied. Residues were determined by using the multi-element capability of Inductively-Coupled Plasma-Mass Spectrometry (ICP-MS). Semi-quantitative analysis was carried out on acid digests of polymer materials, obtained by microwave heating in sealed Teflon containers. Limits of detection in the polymer were generally less than 1 mg/kg. Migration experiments were carried out with three food simulants and under two sets of conditions. Analysis for element residues was performed directly or, in the case of olive oil, on an emulsion of the simulant. Migration of certain elements into aqueous simulants was observed: Zr from polystyrene (650 micrograms/kg), Sb from polyethylene terephthalate (4 micrograms/kg) and Mg from acrylonitrile/butadiene/styrene copolymer (50 micrograms/kg). In all cases, where limits of detection permit, the levels which migrated from polymer to stimulant were less than proposed limits on migration.

Flavour release from a protein-stabilized water-in-oil-in-water emulsion

Abstract The loss of a volatile compound butan-1-ol into the gas phase from a protein-stabilized water-in-oil-in-water (W/O/W) multiple emulsion has been investigated using a head-space analysis technique. Incorporation of the butanol in the multiple emulsion droplets leads to a reduction in the rate of release by about a factor of two.

Determination of trace elements in food contact polymers by semi-quantitative inductively coupled plasma mass spectrometry. Performance evaluation using alternative multi-element techniques and in-house polymer reference materials

The determination of trace elements in a wide range of polymers intended for food contact use was carried out by inductively coupled plasma mass spectrometry (ICP-MS). Microwave digestion in concentrated nitric and sulfuric acids enabled rapid wet oxidation of all the polymers, to give samples suitable for introduction into the plasma. Semi-quantitative multi-element screening of the polymer digests could then be carried out using a single indium internal standard. Limits of detection for the polymers were generally in the order of 1 mg kg–1. Owing to the paucity of suitable standard reference polymer materials required for validation of the procedures used, a series of in-house reference materials was prepared by incorporating a cocktail of metal stearates into a range of polymer materials via the melt. Levels of elements in these reference materials were established by two reference methods: direct neutron activation analysis (NAA) and a quantitative ICP-MS method. Results for the two reference methods were encouragingly close to nominal added values and replicate analyses indicated that homogeneity was good. Further analysis of the materials using laser ablation ICP-MS confirmed that the distribution of elements within the polymer matrix was satisfactory. In addition, NAA was carried out on the great majority of the polymer samples as a further aid to validation of the semi-quantitative multi-element ICP-MS method.

Compositional analysis of samples of thermoset polyester and migration of ethylbenzene and styrene from thermoset polyester into pork during cooking

The levels of ethylbenzene, styrene, benzene and benzaldehyde in samples of thermoset polyester were determined by dynamic headspace/gas chromatography. Styrene was present at levels from 50 to 1400 mg kg-1, ethylbenzene up to 25 mg kg-1 and benzaldehyde up to 180 mg kg-1. Benzene levels were usually less than 1 mg kg-1, but one article contained 19 mg kg-1. Levels of styrene dimers and trimers were estimated using size exclusion chromatography followed by gas chromatographic (GC) analysis and were present at approximately 100 mg kg-1 and 700 mg kg-1 respectively. The principal identified constituents of solvent extracts were stearic and palmitic acids, present at a combined level of nearly 1% by weight of the plastic. Styrene was shown to be produced by thermal depolymerization at temperatures of 175 degrees C and above. The migration of ethylbenzene and styrene into belly pork cooked in thermoset polyester dishes for 1.5 h at 175 degrees C was measured by Likens-Nickerson extraction of the cooked meat and GC/MS analysis of the extracts. Migration ranged from 6 to 2400 micrograms kg-1 for styrene and from < 6 to 34 micrograms kg-1 for ethylbenzene.

Identification of potential migrants from samples of dual-ovenable plastics

The analysis of samples of dual-ovenable cookware articles has identified chemicals with the potential to migrate into food. Samples were analysed by dynamic headspace analysis at 200 degrees C using a Tenax TA trap cooled in ice, and/or solvent extraction, followed by gas chromatography/mass spectrometry. Plastics analysed were crystalline poly(ethyleneterephthlalate) (cPET), thermoset polyester, poly(ethersulphone) and poly (4-methyl-pent-1-ene) (TPX). The greatest number and quantity of chemicals with the potential to migrate were found in thermoset polyester.

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (1

The effect of microwave energy on specific migration from food contact plastics.

Experiments have been carried out with (a) microwave treatment of plastics followed by migration testing using the food simulant, olive oil, and (b) microwave treatment of plastics in direct contact with an organic extractant (iso-octane). In neither of these complementary approaches was there evidence of any difference in migration from plastics that had been microwave-treated compared with plastics that had received an equivalent thermal treatment. Five plastics commonly employed in microwave applications were tested and oligomers, plasticizer, antioxidant and volatile contaminants were monitored as representatives of typical migration species.

Gas—liquid chromatography of thiols using flame-photometric detection and a deactivated transfer line

Abstract 2-Mercaptobenzothiazole and benzotriazole have been assessed as reagents for the deactivation of the transfer line between a glass SCOT-capillary column and a flame-photometric detector operated in the sulphur mode. 2-Mercaptobenzothiazole was only moderately effective but coating with benzotriazole gave excellent results and proved suitable for both isothermal and temperature programmed analysis. The minimum detectable level achieved for butanethiol was 1.0·10 −10 g when a benzotriazole-treated line was used.

Determination of high- and low-molecular-mass plasticisers in stretch-type packaging films

A single analytical procedure is presented for determination of so-called monomeric plasticisers such as di(2-ethylhexyl) adipate, polymeric plasticisers such as poly(butylene adipate), and secondary plasticisers such as epoxidised soybean oil. The plasticisers are extracted from the film with concurrent derivatisation. Ester linkages are cleaved by treatment with potassium hydroxide in ethanol, epoxide moieties are opened using hydrochloric acid generated in situ by addition of acetyl chloride and, lastly, hydroxy groups are converted to silyl ethers using bis(trimethylsilyl)trifluoroacetamide. This reaction sequence is conveniently performed sequentially on a single sample leading to products that can be measured in a single GC analysis. The method has been applied to samples of known provenance and in a large survey of retail stretch-type films. The combined method offers significant savings in time compared with the separate analytical methods published earlier for monomeric and polymeric poly(vinyl chloride) plasticisers. The method is quantitative and gives results in good agreement with these earlier procedures.

Some new volatile compounds from the non-enzymic browning reaction of glucose-glutamic acid system*

ZusammenfassungDie flüchtigen Verbindungen aus der Maillardreaktion des Glucose-Glutaminsäure-Systems wurde mit Hilfe der Gaschromatographie/Massenspektrometrie analysiert. Von den 50 nachgewiesenen Peaks wurden 42 identifiziert: 2 Säuren, 2 Alkohole, 5 Carbonyle, 2 Ester, 4 Lactone, 17 Furane, 4 Pyrazine, 3 Pyrrole und 4 weitere provisorisch. Deca-2,4-dienal, 2-n-Pentylfluorat, 2-(2′-Furyl)-pyrazin, γ-Nonalacton, 2-(2′-Furyl)-5 oder -6-Methylpyrazin wurden bisher nicht in dem erhitzten Zucker-Aminosäuren-Bräunungssystem registriert. Die neue Verbindung 5-Formyloxymethyl-2-furfural ist anscheinend noch nicht in der chemischen Literatur festgestellt worden. Die Verbindung 5-Acetoxymethyl-2-furfural hat an ein Brot erinnerndes Aroma, während die 5-Formyloxymethyl-2-furfural-Verbindung ein sehr schwaches „süßlich-verbranntes” Aroma aufweist.SummaryThe volatile compounds from the Maillard reaction in the glucose - glutamic acid system were analysed by combined gas chromatography - mass spectrometry. Of the 50 peaks detected, 42 components comprising 2 acids, 2 alcohols, 5 carbonyls, 2 esters, 4 lactones, 17 furans, 4 pyrazines and 3 pyrroles were identified, four of which tentatively. Decadien 2,4-al, 2-n-pentyl furoate, 2-(2′-fury()-pyrazine. γ-nonalactone, 2-(2′-fury()-5- or 6-methylpyrazine were previously not reported to occur in heated sugar - amino acid browning systems. The new compound, 5-formyloxymethyl-2-furfural has apparently not yet been recorded in the chemical literature.The compound 5-acetoxymethyl-2-furfural had an aroma close to that of bread whereas 5-formyloxymethyl-2-furfural exhibited a very faint sweet burnt aroma.