Erwin Marti

Purity determination by differential scanning calorimetry

Abstract A review of the literature on the DSC method for purity determination is presented, with a discussion of the most important aspects, i.e. theory, sample handling, calibration of the instrument, evaluation of melting curves, and the conditions and accuracy of the measurement of eutectic impurities. A number of mathematical descriptions of the solid—liquid equilibrium for eutectic binary systems is applied to the calculation of theoretical phase diagrams and specific heat functions, which are then compared with experimental phase diagrams and melting curves. The applicability of the DSC method to systems of solid solutions is discussed. Both the experimental procedure and the evaluation by computer methods required to obtain accurate impurity determinations by DSC are presented. A number of practical examples is included.

Thermal destruction of polychlorinated compounds: Flow tube kinetics of ten dibenzo-para-dioxins

Abstract Thermal decomposition curves of ten chlorinated dibenzo-para-dioxins were measured by a flow tube reactor with integrated gas chromatographic analysis of the reaction products. Residence times between .4 to 1 seconds were chosen for a direct comparison with hazardous waste disposal incinerators. The dependence of the decomposition rates on the carrier gas was studied and the rates were found to increase with added oxygen in nitrogen-oxygen mixtures. All dioxins studied were found to decompose between 850 and 1100°C in nitrogen. The observed decomposition rate constants in nitrogen decreased with increasing chlorination of the dioxins. This finding is in agreement with expectations for pure pyrolysis and suggests that CO bond rupture is the rate determining step.

Thermal analysis, calorimetry and chemical thermodynamics —a review☆

Abstract An attempt is made to review the level of development of the subjects covered by the Swiss Society for Thermal Analysis and Calorimetry, namely thermal analysis, calorimetry and chemical thermodynamics. A comprehensive presentation and elucidation of the stage of development of these subjects seems to be impossible because of the broadness of each of these subjects with respect to theoretical, methodological and instrumental aspects, and also because of the diversity of applied and basic research in this area. The discussion is therefore restricted to such aspects as definitions and the boundaries of these subjects. Furthermore, the importance of chemical thermodynamics in the application to thermoanalytical methods and to applied research is pointed out.

Der einsatz von thermoanalytischen geräten in der chemischen industrie

Abstract Thermal analysis methods are employed in the chemical industry for investigations in the fields of basic and applied research as well as for quality control. The development from qualitative to quantitative thermal analysis has also been extended to chemical industry. We may expect in future an increase in the utilization of thermodynamic relations for the evaluation of experimental data obtained with thermal methods as well as for the description of phenomena related to the characterization of active ingredients and their formulations. A few examples of thermal methods used in elucidating some problems typical of applied research are discussed briefly.

Microcalorimetric investigations of the binding of flavonoids to synthetic and natural membranes.

Abstract The binding of flavonoids of different composition and structure to lipid model membranes and to erythrocyte stroma was investigated by microcalorimetric titration measurements. The affinity constants of the various liposome-flavonoid systems investigated vary from 0.3 to 9.6 10 3 1 M −1 , depending on the chemical structure and the hydrophobicity of the ligands. The enthalpy and entropy terms exhibit large variations, indicating different binding mechanisms for the various flavonoids. The stoichiometry of the lipid - flavonoid complex is 2:1. With erythrocyte membranes the thermodynamics of flavonoid binding indicate that with decreasing hydrophobicity of the ligand, a different flavonoid-binding mechanism, probably to membrane proteins, becomes apparent.