The aim of this work was to identify the degradation compounds produced during irradiation of multilayer polyamide 6 (PA-6) films and to study their migration into water and 95% ethanol food simulant. After irradiation of multilayer PA-6 films at 3, 7 and 12 kGy, degradation compounds were extracted using solid-phase microextraction, for which the time and temperature of extraction and stirring were optimized, and identified by gas chromatography-mass spectrometry. Caprolactam, 2-cyclopentylcyclopentanone and aldehydes, among other compounds, were identified in the headspace of the films. Polydimethylsiloxane was considered the best fiber for extraction. The optimum conditions of time, temperature and stirring to extract the compounds were 20 min, 80 degrees C and 225 rpm. For validation purposes, the compounds were quantified in water and 95% ethanol and the results showed high sensitivity, good precision and accuracy. Migration of compounds from irradiated and non-irradiated multilayer PA-6 films into water and 95% ethanol food simulants was carried out at 40 degrees C for 10 days. The method was efficient for the quantification of decaldehyde, 2-cyclopentylcyclopentanone and caprolactam that migrated from multilayer PA-6 films into food simulants.

The possibility of using recycled polyethylene terephthalate as a food contact material is being seriously considered, but the potential migration of nonvolatile compounds from it must be assessed to ensure that it is safe to do so. In the study presented here, four samples of recycled PET were each exposed to three food simulants under the harsh extraction conditions stipulated by European legislation regarding migration tests. The nonvolatile compounds that migrated from them were determined by ultra performance liquid chromatography-mass spectrometry using three different cone voltages, and both positive and negative ionization modes. A total of 36 chemical compounds were detected, some of which were identified, including common additives such as N,N'-di-beta-naphthyl-p-phenylenediamine (antioxidant) and 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)phenol (light stabilizer) as well as degradation compounds such as ethylene terephthalate dimers and trimers. In addition, specific migration values of three common components of polyethylene terephthalate (diethylene glycol, terephthalic acid, and isophthalic acid) were determined and found to occur at levels of <1 mg/kg-much lower than the specific migration limits stipulated by European legislation.

No abstract

An analytical strategy has been proposed and optimized to study the permeability of several flexible plastic materials, some of them with high-barrier properties, versus naphthalene, methyl bromide, toluene, ethylbenzene, and ortho-and para-xylenes. The strategy involves using a system of concentric plastic bags made from the materials to be tested polyethylene (PE) and used as permeable plastics to facilitate the homogeneous distribution of a solid compound, such as naphthalene, in vapour phase. After the permeation test, the vapour phase containing the pollutants that cross the plastic barrier is trapped in a 12% ethanol-water solution and further analysed by SPME in headspace mode. Several experimental conditions as well as different samples were tested. The results obtained are shown and discussed.

It has been possible to perform the simultaneous determination of choline and glucose using the intrinsic fluorescence of the corresponding enzyme as an analytical signal. This can be done in two ways. First, for low glucose and choline concentrations (about 0.55 mM and 0.75 microM respectively) two differentiated signals, without mutual interference, are obtained for both analytes in the same measurement. Second, when glucose and choline concentrations are higher, a new model has been designed which permits the concentrations to be accurately determined in samples containing from 0.55 mM to 3.75 mM glucose and from 0.75 microM to 11.0 microM choline; the method has been applied to simultaneous glucose and choline determinations in serum samples with good results. This method gives a better performance than multivariate calibration based on Partial Least Squares Regression. The methodology here shown could be also used for the simultaneous determination of other pairs of analytes.