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  • Author or Editor: J. Afonso x
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Abstract  

We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong to the class of relatively strong glass-forming systems.

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A high-performance thin-layer chromatographic (HPTLC) method has been developed for determination of polyamines in beers. Beer samples, previously degassed, were derivatized with dansyl chloride and the dansyl derivatives were separated by HPTLC with silica gel as stationary phase and chloroform–triethylamine, 2 + 1 (v/v), containing 5% (m/v) polyoxyethylene-10-lauryl ether, as mobile phase. Quantitative analysis was achieved by in-situ fiberoptic-based fluorescence scanning. The compounds were determined over the range 0.5–85 ng, with relative standard deviations between 0.44–1.16% and detection limits in the range 0.28–0.39 ng. The simple preparation of the sample and the rapid microwave-assisted dansylation considerably reduce analysis time and effort.

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