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Study of the Dispersive Component of the Surface Energy of Polylactides by Inverse Gas Chromatography at Infinite Dilution

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American Journal of Analytical Chemistry 2020年第3期11卷 129-136页

作者： Carla Zarazir mohamad rajab Houssam Obeid Joumana Toufaily Imad Toufeili Tayssir Hamieh Laboratory of Materials Catalysis Environment and Analytical Methods Laboratory (MCEMA) Lebanese University Hadath Lebanon Laboratory of Applied Studies to the Sustainable Development and Renewable Energies (LEADDER) EDST Lebanese University Hadath Lebanon Department of Nutrition and Food Sciences American University of Beirut (AUB) Beirut Lebanon

Inverse gas chromatography at infinite dilution is a powerful technique that can be advantageously used to characterize the surface physicochemical properties of solid substrates as oxides and polymers in both forms of powder or fibres. In the case of polymer, this technique can be used to determine the second order transition phenomena temperatures. This paper was devoted to the determination of the glass transition temperature of polylactide polymer. The dispersive component of the surface energy ?of polylactides was determined by inverse gas chromatography at infinite dilution. Various theoretical models were used to deduce the dispersive component of the surface energy of the solid substrates. These models are based on the calculation of the molecular areas of adsorbed molecules on the polymer surface: geometrical model, cylindrical molecular model, liquid density model, BET method, Kiselev results and the two-dimensional Van der Waals and Redlich-Kwong equations. The curves relative to the variation of as a function of the temperature showed a specific graph with a maximum value of ?at a certain particular temperature characteristic to the investigated polylactide polymer. In fact, the maxima of ?indicated the presence of glass transition temperature Tg of polylactide whatever the molecular model used. This study showed a glass transition temperature equal to 64°C confirming that obtained by other studies.

关键词： Adsorption Surface Area Surface Energy Retention Volume N-Alkanes Equations of State

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Impact of Plastic Packaging Materials and Storage Time on the Quality Parameters of Lebanese Extra Virgin Olive Oil under Real-Time Storage Conditions

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American Journal of Analytical Chemistry 2019年第12期10卷 647-665页

Scarce information is currently available relative to the use of polymeric materials as storage containers for extra virgin olive oil. This paper was devoted to study and compare the impact of glass and 3 types of packaging materials—polyethylene terephthalate (PET), high density polyethylene (HDPE), and polylactic acid (PLA) on Lebanese extra virgin olive oil (EVOO) up to 9 months under non-accelerated storage conditions. The acidity, peroxide value (PV), K232, K270, fatty acid profile, overall migration, and oil sorption into the packaging material were determined. Conventional titration, gas chromatography-mass spectrometry, and spectrophotometry were used to quantify the outcome measures at baseline, 3, 5, 7, and 9 months. Mixed model ANOVA was applied to assess differences according to polymer type and storage period at P 232 and K270), migration, and sorption significantly increased with increasing storage time for oil in contact with glass and plastic materials, especially between the 7th and 9th month of storage. Overall, PLA showed the least deterioration and interaction phenomena compared with PET and HDPE. While glass remains the best container for EVOO, PLA could potentially replace PET and HDPE for short-time storage under conventional storage conditions in Lebanese households.

关键词： Extra Virgin Olive Oil Polymer Storage Overall Migration Fatty Acids

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