Tips & Tricks
Calibration is a fundamental requirement for thermoanalytical investigations. The knowledge of a quantitatively defined relationship between the value indicated by the measuring instrument and the correct value is essential.
Calibration of modern Differential Scanning Calorimeters (DSC) and Simultaneous Thermal Analyzers (STA) is achieved by quantification of the produced signal when a known quantity of energy is generated within the system. The calibration procedure consists of measuring thermal properties of standard materials which are well known.
Experimental conditions of calibration and measurement should be matched as closely as possible: not only the quantity of energy to be measured must be similar but the site and kinetics of the generation and temperature range should be as close as possible in both calibration and measurement experiments. All the results of subsequent measurements depend on the validity of the calibration. Therefore, it is mandatory to carefully carry out all calibration procedures.
Reference materials must be homogeneous and stable, and the certified values must be accurate. Finding a material that can be used as a reference for more than one property is one of the goals of current research.
Various calibration kits and individual standards are available for each thermoanalytical method presen-ted (DSC, TGA and STA) allowing the instrument to be calibrated across its entire temperature range and allowing for the use of different crucible types. The table gives an overview of possible combinations of calibration and crucible materials.
|Common Calibration Materials/Phase Transition Temperature||Crucible Materials|
✓ No solubility or effects on the Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).melting temperature expected
! Corrosion reactions possible with negligible changes in the melting temperature
- Melt or transformation product reacts with the crucible material. Changes in the melting temperature can be expected.
* Special preparation of the crucible necessary