Thermomicroscopy–calorimetry applied to chemical and biological systems

This paper describes how a minimally modified Calvet calorimeter (Setaram C80), equipped with a digital microscope, can effectively correlate morphological and colour changes with energetic transitions. This combined approach enhances the interpretation of thermodynamic events by correlating heat flow with visual changes. The system’s capabilities were demonstrated across a range of applications. Thermochromic behaviour observed in both a leuco-dye and an inorganic complex where distinct colour transitions corresponded with endothermic phase changes as confirmed by calorimetric data and total colour profiles. The isothermal crystallisation of nitrobenzaldehyde was studied at 40 °C and showed a clear link between the exothermic heat flow and micrographs of crystal growth. This was also observed in an experiment where the addition of 5% silica caused the retardation of this crystallisation by 200 min. The weak enthalpic signal of egg white protein denaturation at 68 °C was observed in real time through changes in the sample opacity, highlighting the potential of the technique for biological studies. The monitoring of fly larval development of both Lucilia sericata and Musca domestica utilised both the direct calorimetry and micrographs to readily distinguish between larval, pupal, and adult fly stages. This allowed for the accurate determination of pupation period, a feature of importance in entomological studies.