Rodrigo SILVA1, Ana I. M. C. LOBO FERREIRA1, Luís M. N. B. F. SANTOS1
1CIQUP, Institute of Molecular Sciences (IMS) – Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Porto, Portugal
This work presents the refurbishment, upgrading and testing of a differential scanning microcalorimeter - iSenseDSC. Several changes were made to the original apparatus (SETARAM micro DSC III) in order to better its performance. With the aim of improving the temperature stability, the original heat pumping and exchanging system was replaced by a more modern and efficient system (produced by Laird Thermal Systems), the location of the temperature control point was changed, and a temperature control module was built. Furthermore, the overall insulation of the calorimeter was reinforced. To enhance the calorimetric signal’s quality, a new pre-amplification system (originally developed in the former Thermochemistry Laboratory of the University of Lund) was installed.
Some of the evaluated parameters include the temperature stability, calorimetric noise level, time constant, calorimetric signal linearity and temperature dependence of the calorimetric sensitivity. The temperature was calibrated by means of a reference probe. The changes allowed the achievement of a temperature stability better than ± 0.5 mK, a calorimetric signal noise level around ± 50 nV and a calorimetric sensitivity ranging from 100 (at T = 283 K) to 110 mV/W (at T = 333 K).
For the high precision heat capacity measurements, the incremental temperature step method was adopted. Blank area was determined, and sapphire (NBS SRM 720) was used as calibrating substance. The overall performance of the system was tested by measuring the heat capacity of some recommended substances, namely benzoic acid, anthracene and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonylimide) ([C6C1im][NTf2]). The obtained results revealed low dispersion (0.5 %) and an uncertainty better than 1 % (in the temperature range from 283 to 333 K).
When comparing the data obtained with the new iSenseDSC microcalorimeter system (refurbished and upgraded version of the SETARAM microDSC III) and data reported in the literature obtained with high precision techniques (namely adiabatic calorimetry and drop microcalorimetry), small deviations were found (> ±0.5 %).
Acknowlegdements
This work was supported by the Fundação para a Ciência e Tecnologia (FCT) (funded by national funds through the FCT/MCTES (PIDDAC)) to CIQUP, Faculty of Science, University of Porto (Project UIDB/00081/2020), IMS-Institute of Molecular Sciences (LA/P/0056/2020). RMAS is grateful to FCT for the award of his PhD grant (U1/BD/153093/2022). AIMCLF is also financed by national funds through the FCT-I.P., in the framework of the execution of the program contract provided in paragraphs 4, 5 and 6 of art. 23 of Law no. 57/2016 of 29 August, as amended by Law no. 57/2017 of 19 July.