Microalgae cells have the potential to rapidly accumulate lipids, such as triacylglycerides that contain fatty acids important for high value fatty acids (e.g., EPA and DHA) and/or biodiesel production. However, lipid extraction methods for microalgae cells are not well established, and there is currently no standard extraction method for the determination of the fatty acid content of microalgae. This has caused a few problems in microlagal biofuel research due to the bias derived from different extraction methods. Therefore, this study used several extraction methods for fatty acid analysis on marine microalga Tetraselmis sp. M8, aiming to assess the potential impact of different extractions on current microalgal lipid research. These methods included classical Bligh & Dyer lipid extraction, two other chemical extractions using different solvents and sonication, direct saponification and supercritical CO2 extraction. Soxhlet-based extraction was used to weigh out the importance of solvent polarity in the algal oil extraction. Coupled with GC/MS, a Thermogravimetric Analyser was used to improve the quantification of microalgal lipid extractions. Among these extractions, significant differences were observed in both, extract yield and fatty acid composition. The supercritical extraction technique stood out most for effective extraction of microalgal lipids, especially for long chain unsaturated fatty acids. The results highlight the necessity for comparative analyses of microalgae fatty acids and careful choice and validation of analytical methodology in microalgal lipid research.

Formation of homo-interpenetrating polymer networks (homo-IPNs) of poly(2-hydroxyethyl methacrylate) (PHEMA) and their capacity for calcification are investigated. A sequential method is established to generate IPNs of rank I and II, containing two or three crosslinked networks. Although the networks are chemically identical, thermo-mechanical analysis (DSC, DMA) suggests some phase separation. Calcification of PHEMA hydrogels, thought to be controlled by the free volume pathways accessible to calcium ions, is investigated by positron annihilation lifetime spectroscopy (PALS) and experimental calcium deposition. While calcium uptake is reduced in IPNs, the size of the free volume elements estimated by PALS remain constant at radii of 2.6 Å (dry) and 2.9 Å (hydrated), both in PHEMA and IPNs. The reduction of calcium uptake cannot be therefore associated with the size reduction of the angstrom-size free volume elements detectable by PALS, and is attributed to the effect of chain packing on pores too large to be detected by PALS. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: E455-E466, 2012

Photo-oxidation at the exposed surfaces of low-density polyethylene/montmorillonite composites was analyzed with attenuated total reflection/Fourier transform infrared spectroscopy. It was found that the clay particles were dispersed but not exfoliated in the polymer matrix. The extent of oxidative degradation of the lowdensity polyethylene matrix was slightly greater when montmorillonite was present and was greatest for the blend of low-density polyethylene and organically modified montmorillonite. The Fourier transform infrared measurements demonstrated that the rate of photo-oxidation in the bulk was lower than that observed at the surface, but the oxidation chemistry was similar at the surface and in the bulk. The distribution of the photo-oxidation products was somewhat modified in the presence of montmorillonite and organically modified montmorillonite in comparison with pure low-density polyethylene, with the yield of acidic products higher and the yield of double bonds lower. These observations were attributed to a slightly higher yield of radicals and some modification of the quantum yield for the processes leading to the formation of double bonds when the clay filler was present.