The thermal stability of AB-type carbonated calcium phosphate apatites prepared by precipitation from aqueous media was studied. The behavior of powders was investigated using temperature programmed XRD, infrared spectroscopy and thermogravimetry. In N2 atmosphere, two successive peaks of decarbonatation with maxima at about 700 and 950C occurred. This behavior is explained by different substitution modes for carbonates in the apatite. The decarbonatation peaks were shifted to higher temperature under CO2 (around 900 and 1150°C). The analysis of the thermal stability allowed further densification of carbonate apatite ceramics without important carbonate loss.

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International audienceA technique of immobilizing very thin layer of enzymes over glass electrodes, resulting in response times as low as 5-10s, is described. The method involves the adsorption of enzyme molecules onto the sensitive end of the glass electrode followed by the formation of covalent bonds between the enzyme molecules, by means of spraying a dilute solution of glutaraldehyde over the surface. Enzymes immobilized in this manner over pH glass elctrodes are acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), penicillinase, and urease. The cross-sectional scanning electron micrograph of the fractured surface of the electrode shows the immobilized layer is not more than 1-2 µm thick. The technique could offer immense scope for immobilization of other protein substances as thin layers on different support surfaces

International audience9-hydroxyl derivative of ellipticine, compound of current interest known for its antitumor activity, shows a degradation in a reverse-phase column during High-Performance Liquid Chromatography analyses. In this paper, a chemical explanation of this phenomenon is proposed with the help of a degradation mechanism previously plubished, to understand the appearance of additionnal peaks corresponding to other products