Purity Determination

Purity Determination is a program for determining the purity of a material through analysis of the DSC melting peak.

The following features set this program apart from the known solutions as well as from ASTM E 928:

  • determination of purity using the VAN'T HOFF equation without a mathematical approximation. Thus, the range of application can be extended beyond the threshold of impurity of 5 mol%. The estimated upper boundary could be 10 mol%
  • adjustment of the thermal resistance in such a way that the nominal value is calculated for a substance with a known degree of purity. This yields not only a high degree of precision in the high purity range, but substances of a lower purity can be used to determine the thermal resistance

The names and the molar masses of the substances used are stored in a table and are available after every start. ASCII-Files serve as the general interface for the transfer of data. The data can be corrected using three different baselines:

  • linear,
  • horizontal area-proportional and
  • tangential area-proportional.

The non-linear regression automatically links with the baseline determination. The required initial parameters are prepared in a starting calculation.

Error in purity determination caused by approximation routines.Error in Purity Determination caused by approximation routines.

To increase reliability, the results of several measurements can be averaged and the mean printed out with the standard deviation.

These errors are avoided in NETZSCH Purity Determination by using a non-linear regression routine.

The following are listed in the results:


Name of ParameterResult
Impurity/mol%concentration of the impurity(ies)
To/°C melting temperature of the pure substance, extrapolated temperature for 1/Partial Area => 0.
TempClear/°Ctemperature is obtained through extrapolation of 1/Partial Area ->1.
TempBegin/°Ctemperature for which the Partial Area = 0.1,
Correction/%correction of the peak area
Enthalpy/(kJ/mol)melting enthalpy of the substance (measured from the DSC peak).


The results can be printed out with the graph.