Validation of the rancimat test for the assessment of the relative stability of fish oils

The induction periods for the peroxidation of various fish oils at 55–90°C were studied by the Rancimat test. The natural logarithms of the induction periods varied linearly with respect to temperature, with a mean coefficient of −7.5×10⁻²°C⁻¹, which was significantly different from that reported for vegetable oils. The activation energy for the formation of volatile acids had a mean value of 38.9 kJ/mol and was independent of the fish oil source. Peroxide formation under Rancimat test conditions followed first-order kinetics. The same kinetics were followed under Schaal Oven test conditions (forced-air oven, 60°C). On the basis of the results obtained, the Rancimat test appears to be useful in determining the relative stabilities of fish oils without the change in peroxide decomposition kinetics that may occur at elevated temperatures.     

Reduction of Cu(II) to Cu(I) in solid CsCuCl3

The solid state reaction Cu + Cu²⁺ → 2Cu⁺ in CsCuCl₃ was studied at 499 K using a cell in which the Cu(II) sample was put between two copper discs. Mass changes, thickness of the product layer and the total electrical resistance of the cell were measured as a function of time, both with and without (spontaneous) applied voltage.     

Recovery of platinum, tin and indium from spent catalysts in chloride medium using strong basic anion exchange resins

This work describes a route for platinum recovery from spent commercial Pt and PtSnIn/Al₂O₃ catalysts using strong basic mesoporous and macroporous anion exchange resins (Cl⁻ form). The catalysts were leached with aqua regia (75 °C, 20-25 min). Platinum adsorption was influenced by the presence of other metals which form chlorocomplexes (tin, indium) and also base metals (aluminum). However, it was possible to overcome this fact by a sequential desorption procedure. Aluminum was selectively removed from the resins by elution with 3 mol L⁻¹ HCl. Platinum was desorbed passing 1 mol L⁻¹ Na₂S₂O₃ (pH 9). Tin was removed by elution with 0.1 mol L⁻¹ ascorbic acid. Indium was removed using 0.1 mol L⁻¹ EDTA as eluent. Desorption efficiency exceeded 99% for all metals. Metals were recovered in high yields (>98 wt%).     

Production and purification of a fused recombinant protein gp-36 (HIV-2) from Escherichia coli

A fragment of the gp-36 gene of the Human Immunodeficiency Virus type 2 (HIV-2) was fused to a stabilizer sequence, which encodes for the first N-terminal 58 amino acids of the human interleukin-2. The fused protein was expressed under the control of the tryptophan promoter in Escherichia coli, and expressed as 20% of the total cellular protein. Transmission electron microscopy indicated that the fusion protein formed cytoplasmic insoluble inclusion bodies. Inclusion bodies were semipurified by a wash pellet cell procedure, rendering a material with a purity higher than 70% by SDS–polyacrylamide gel electrophoresis. After solubilization with urea, this preparation was further purified by gel-filtration chromatography up to 95% purity.     

Studies of polymerization of acrylic monomers using luminescence probes and differential scanning calorimetry

A fiber optic system has been designed to couple calorimeter and fluorimeter equipment for in situ monitoring of polymerization reactions by both techniques simultaneously. Two acrylic monomers (cyclohexyl methacrylate, CHM, and 2-ethylhexyl acrylate, EHA) were studied at different temperatures. Pyrene (Py) was employed at a low concentration (≤10^?4 mol/L) as a fluorescence probe. The emission spectrum of pyrene shows a broad band peaking at 390 nm, whose intensity grows with polymerization progress. A correlation with conversion degree could be established by collecting fluorescence intensity through the optical fiber at different polymerization times. For the more flexible polymer formed, poly(ethylhexyl acrylate) (PEHA), Py emission sharply increases only when high conversions are reached and continues increasing for a long time after the limiting conversion is attained. For CHM polymerizations, S-shaped curves are found. Isochronal plots of intensity vs. scaled conversion allow elaboration of master curves for the peak emission. Data at 50°C for CHM cannot be fitted to the master curve, and this is explained in terms of vitrification.