Development of a solid-phase microextraction method for direct determination of pentachlorophenol in paper and board samples: Comparison with conventional extraction method

A solid-phase microextraction (SPME) method has been developed for the determination of pentachlorophenol (PCP) in paper and board samples. The analytical procedure involves direct extraction of PCP from paper and board samples and determination by gas chromatography with electron capture detection (GC-ECD). Two kinds of commercially available fibres; 100 microm polydimethylsiloxane (PDMS), apolar, and 85 microm polyacrylate (PA), quite polar, were evaluated to determine the extraction efficiency of pentachlorophenol. Parameters affecting the extraction process, such as temperature and time, were studied. Moreover, time of desorption and the effect of addition of salt were also investigated. The optimized procedure was applied to the analysis of pentachlorophenol (PCP) in five samples of virgin and recycled paper and board. The PCP content was determined by GC-ECD. To evaluate the effectiveness of the proposed method, it was compared with conventional extraction method with liquid-liquid extraction and derivatization. Detection limit of 0.015 microg/g for PCP in paper was achieved with a RSD of 14%.

Solid- and vapor-phase antimicrobial activities of six essential oils: susceptibility of selected foodborne bacterial and fungal strains

The antimicrobial activity of essential oils (EOs) of cinnamon (Cinnamon zeylanicum), clove (Syzygium aromaticum), basil (Ocimum basillicum), rosemary (Rosmarinus officinalis), dill (Anethum graveolens), and ginger (Zingiber officinalis) was evaluated over a range of concentrations in two types of contact tests (solid and vapor diffusion). The EOs were tested against an array of four Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, and Listeria monocytogenes), four Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Salmonella choleraesuis, and Pseudomonas aeruginosa), and three fungi (a yeast, Candida albicans, and two molds, Penicillium islandicum and Aspergillus flavus). The rationale for this work was to test the possibility of creating a protective atmosphere by using natural compounds that could extend the shelf life of packaged foodstuffs while minimizing organoleptic alterations. In the solid diffusion tests, cinnamon and clove gave the strongest (and very similar) inhibition, followed by basil and rosemary, with dill and ginger giving the weakest inhibition. The fungi were the most sensitive microorganisms, followed by the Gram-positive bacterial strains. The Gram-negative strain P. aeruginosa was the least inhibited. The composition of the atmosphere generated by the EOs, and their minimum inhibitory concentrations (MICs), were determined using a disk volatilization method, in which no inhibition from rosemary or basil was observed. Cinnamon and clove, once again, gave similar results for every microorganism. As a general rule, MIC (fungi) << MIC (bacteria) with no clear differences between Gram-positive or -negative strains except for P. aeruginosa, which was not inhibited by any of the EOs in the vapor phase. The atmosphere generated from the EOs was analyzed by means of solid-phase microextraction combined with gas chromatography-ion trap mass spectrometry. Differences among the volatiles in the EOs, which may be responsible for the differences in their antimicrobial performances, were found.

Supercritical Fluid Extraction of Energetic Nitroaromatic Compounds and Their Degradation Products in Soil Samples

This paper explores the use of supercritical fluid extraction (SFE), in combination with various analyte collection strategies, for extracting energetic nitroaromatic compounds and their degradation products from soil samples. The required selectivity has been achieved by a combination of an SFE program and active trapping. Several different collection strategies were tested, using a selection of liquids (methanol, toluene, methyl tert-butyl ether, acetonitrile), inert and solid-phase extraction materials (Nexus, Oasis, LiChrolut), and 1-cm liquid chromatography precolumns (porous graphitic carbon, PGC). The best results were obtained using SFE in combination with a PGC precolumn. This setup allows on-line cleanup of the extract, and comparable results were obtained using either GC-ECD or GC-chemical ionization-MS for confirmatory analysis. The time required for a complete analysis was less than 60 min, and only 1 mL of toluene was needed for a 0.5-g representative sample. In contrast, the EPA standard method 8330 required 18-h sonication and 20 mL of acetonitrile for a 4.0-g sample and further time for sample cleanup and HPLC analysis. The method presented here provides method detection limits in the low-nanogram range, with relative standard deviations lower than 7%. The optimized method has been compared and validated with EPA method 8330 in terms of efficiency parameters such as robustness, accuracy (trueness and precision), and capability of detection. The validation demonstrated that the two analytical methodologies give comparable performance for the determination of nitroaromatic compounds, but SFE is superior for analyzing amine degradation products.

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.

Potential migration release of volatile compounds from plastic containers destined for food use in microwave ovens

Several commercially available plastic containers of polycarbonate, polypropylene-copolymer, polypropylene-20% talcum, polypropylene random and styrene-acrylonitrile designed for heating food in microwave ovens were studied. The analytical procedure based on a purge & trap (P&T) GC-MS was optimized. It consisted of heating the materials at 100 degrees C in a P&T system coupled in line with GC-MS equipment. The compounds released from the materials were then identified through their mass spectra. Variables such as the time of purge using helium as the carrier gas in the system, sample temperature, the type of solid trap, the desorption temperature and the time as well as chromatographic separation of all the compounds released from the plastic were optimized. Compounds such as methylbenzene, ethylbenzene, 1-octene, xylene, styrene and 1,4-dichlorobenzene were found in all the containers. Quantitative analysis and potential migrations are reported and discussed.

Determination of plastic monomers in water by solid-phase microextraction coupled with liquid chromatography

A method is presented for the determination of 2 major plastic monomers, terephthalic acid and vinyl acetate, which are widely used to manufacture plastics that come in contact with foods. The analytes are extracted from aqueous solution by using solid-phase microextraction, followed by quantitation by liquid chromatography (LC) with UV detection. Multivariate optimization was applied and is described. The optimized method has linear ranges of 5-150 microg/g for terephthalic acid and 7.5-100 microg/g for vinyl acetate. Coefficients of variation at a spiking level of 20 microg/g were 13.6% for terephthalic acid and 3.1% for vinyl acetate; detection and quantitation limits were 0.59 and 1,99 microg/g, respectively, for terephthalic acid and 1.56 and 5.20 microg/g, respectively, for vinyl acetate. The characteristics of both the extraction technique and its coupling with LC are described and discussed.

Use of solid-phase microextraction for the analysis of bisphenol A and bisphenol A diglycidyl ether in food simulants

A new method has been developed to simultaneously analyse bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) in aqueous based food simulants. The method consists on direct immersion solid-phase microextraction (SPME) of the analytes from the liquid matrix and subsequent chromatographic analysis by gas chromatography-mass spectrometry. Using the proposed method, a whole analysis (including chromatographic step) can be completed in less than 40 min, with minimum sample handling. The SPME method shows good analytical performance for simultaneous BPA and BADGE analysis, except for BADGE determination in the aqueous alcohol (simulant C) solution. Detection limits ranging from 0.1 to 2.0 ng/g for BPA and from 13 to 15 ng/g from BADGE were obtained, with a linear range from the low-ng/g to several-microg/g range for BPA and from 0.1 microg/g to 40 microg/g for BADGE. A possible optimisation method has been also developed and introduced.

Distribution of Pb, V, Cr, Ni, Cd, Cu and Fe in particles formed from the combustion of waste oils

The determination of Pb, V, Cr, Ni, Cd, Cu and Fe in particles of different size obtained from the combustion of waste oils has been carried out. The study consists of the separation of several fractions according to the size of particles, the wet digestion and the individual analysis by graphite furnace atomic absorption spectrometry of the mentioned metals. Taking into account the volatilization temperature of different compounds containing the metals and their distribution on the size fractions, the mineral speciation of metals is proposed.

Assessing the suitability of recycled plastics used as agricultural soil covers: migration study and experimental harvest

The present work is focused on evaluating the suitability of recycling postconsumer agricultural plastic films again for the same use. The criteria to assess the suitability was based on migration study. Both overall and specific migration tests were performed, and the results obtained (ranging from 0.14 to 1.27 mg/dm(2) for overall migration and from not detectable to 6.98 microg/dm(2) for specific migration) show how, from this point of view, the recycled material can be safely proposed to be used again as agricultural soil covers. A theoretical discussion about the migration process is also presented and a simple mathematical model was applied to the data obtained, showing how total migration which is experimentally detected is theoretically predictable. These conclusions found were used to design and develop a controlled crop of tomato by using this recycled film. The use of the recycled plastic in the whole process and the behavior and properties of the pesticides absorbed in the postconsumer film are discussed.

Multicomponent recycled plastics: considerations about their use in food contact applications

Two multicomponent post-use recycled plastics named as NPP40A3 (formulated with 85% HDPE and 15% of a PP-PS-PVC mixture) and NPP40A6 (formulated with 80% NPP40A3, 10% ABS and 10% HIPS), both of them with 3.1% of plasticizer and 0.6% of stabilizer to obtain a better final product, have been analysed. Plastics were extracted both with dichloromethane and methylbenzene, and analysed by HPLC and GC-MS to identify the maximum possible number of compounds. Major additives quantified were di(ethylhexyl)phthalate (3.262% and 2.955% respectively) and Irganox 1010 (0.473% and 0.498% respectively). Several degradation compounds have been detected. In order to check if these plastics could be used in food contact applications, global and specific migration tests have been applied. The results obtained are discussed.

Speciation of ionic alkyllead compounds in human urine by gas chromatography-mass spectrometry after butylation through a Grignard reaction

One analytical procedure for the determination of ionic alkyllead in human urine has been studied. The system consists of the extraction of Me3Pb+, Et3Pb+ and Pb2+ at pH 9.0 with diethyldithiocarbamate to an organic phase. Then, the ionic compounds are butylated with BuMgCl and the final organic solution is analyzed by GC-MS-SIM. The elimination of both foam and gels in the extraction step and the general procedure for the urine are discussed. The recovery of compounds ranges from 105.1% for Me3Pb+ to 97.2% for Et3Pb+ using hexane as extracting agent and detection limits are 18.4 pg/ml of Me3Pb+ and 19.2 pg/ml of Et3Pb+ in urine. The speciation of ionic alkylleads in the urine of a petrol station worker showed a value of 27.9 pg/ml of Me3Pb+ in urine and Et3Pb+ was below the detection limit.

Parts-per-trillion determination of styrene in yoghurt by purge-and-trap gas chromatography with mass spectrometry detection

Headspace sampling methods prior to capillary gas chromatography have been widely used for the determination of volatile compounds present in very different kinds of samples. This paper describes an automated and rapid system to determine volatiles from yoghurt. Thirty-five volatile organic compounds (VOCs) were identified in polystyrene cups used for yoghurt packaging and 42 VOCs from yoghurt samples. Quantitation of styrene in several samples from the Spanish retail market was carried out.

Design of a test for migration studies in the vapour phase

A new test for migration studies in the vapour phase has been developed. The system consists of placing the packaging material containing the potential migrants in a glass vial together with the solid adsorbent, Tenax GC. The vial is introduced into an oven at a controlled temperature for different periods of time. Once the migration test has finished, Tenax is extracted by supercritical fluid chromatography (SFE) and analysed by GC-ECD. Migration conditions of 7 days at 80 degrees C are proposed. The results obtained are discussed.

Determination of UV stabilizers in PET bottles by high performance-size exclusion chromatography

A Size Exclusion Chromatography-High Performance Liquid Chromatography (SECHPLC) method to determine antioxidants and UV stabilizers in PET bottles has been developed. In only a single run a synthetic mixture of the stabilizers was separated and quantified. The detection limit obtained for BHT, Tinuvin 326, Cyasorb UV 5411, and Tinuvin P was about 0.1 microgram/g and for Irgafos 168 it was 1.0 microgram. RSD values were lower than 3%. Tinuvin P was identified and quantified in PET bottle extracts. Olive oil, soybean oil and sunflower oil showed well defined separation from Tinuvin P at the same conditions of analysis. Cyclic dimers were identified in the PET extracts.

Behaviour of Chimassorb 81 in the recycling process of agricultural films used as soil covers

Two different films, low density polyethylene (LDPE) and an ethylene-vinyl acetate copolymer (EVA), used as agricultural soil covers were studied. The films were recycled five and ten times respectively, and both the tensile strength and the content of Chimassorb 81, a UV-stabilizer, were analysed in each cycle. Losses of 17.44% in tensile strength and 23.69% (Thermic film) and 13.22% (EVA) in the concentration of Chimassorb 81 were found after five recycling cycles. The extraction of Chimassorb 81 from the film is optimized. As these films can be recycled for the same application or even for use as food-contact materials, the standard migration tests with established simulants have been carried out. The results obtained are discussed.