Mesure DSC avec observation visuelle
Les courbes DSC présentent souvent des effets qu'il est impossible de comprendre. Dans ce cas, il est très utile d’observer ce qui se produit dans l’échantillon.
Dispositifs inclus dans l’option de microscopie
Un système de microscopie DSC contient une caméra CCD dotée d’un logiciel de capture et de traitement d’images synchronisé avec le programme de température DSC.
Possibilité de mise à niveau
Il est possible de mettre à niveau un système DSC vers un système de microscopie DSC en une minute, y compris la capacité de mesure de microscopie en lumière réfléchie.
Matériel No.: 51143087
Technique | Calorimétrie différentielle à balayage (DSC) |
Type | Analyse optique |
Accessoire | oui |
Option | Non |
| DSC-microscopy analysis of an active pharmaceutical ingredient The melting point is an important characteristic property of a substance. The DSC measurement of an active pharmaceutical substance (API) yielded a curve with two main peaks – an endothermic peak with a maximum at 210.8 °C and an exothermic peak at about 228 °C. A smaller peak was also apparent between these two peaks at about 214 °C. The initial interpretation was that the endothermic peak at 210.8 °C is due to melting. The DSC-microscopy results, however, told a different story. No melting was observed at 211 °C – the first signs were detected at about 214 °C. Clearly, the endothermic DSC peak is not caused by a melting process. The color change of the molten substance leads one to conclude that it decomposes immediately on melting. The small DSC peak observed at about 214 °C is therefore the sum of two simultaneously occurring effects – endothermic melting and exothermic decomposition. Separate TGA-MS measurements showed that the endothermic DSC peak at 210.8 °C is caused by the evaporation of water of crystallization. | |
Dehydration of CoCl2 hexahydrate The images illustrate the dehydration process of cobalt (II) chloride hexahydrate when it is heated from 30 °C at 1.5 K/min. The initial ruby-red color becomes lighter and lighter until it suddenly changes at about 55 °C. Further color changes are observed between 100 °C and 120 °C and at 160 °C. The differences can be quantified by calculating a curve showing image brightness as a function of temperature. The DSC curve shows a broad endothermic peak up to 80 °C with a sharp peak at about 55 °C superimposed on it. Two further endothermic peaks follow at about 104 and 130 °C. The brightness first increases and then suddenly decreases at about 55 °C. Afterward, it increases again in several steps. The peak at about 55 °C is due to a change in crystalline structure. The images around 55 °C show small droplets of water on the surface of the crystals. This indicates that part of the water of crystallization eliminated from the crystal lattice during the solid- solid transition collects on the surface of the crystals and then evaporates. This is completed by about 80 °C. The two broad endothermic peaks on the DSC curve and the step-like changes in the brightness are due to further loss of water of crystallization. |