Several reference materials
and associated reference values have been recommended for the purposes of
calibration and/or validation of differential scanning calorimetry (DSC).
However, issues of available sample purity, reference-property value accuracy,
and potential undesired reactions between reference materials and the materials
used for sample pans have not been considered sufficiently in some of the
recommendations of property values for the materials. These limitations attenuate
greatly the usefulness of many of these reference material recommendations.
Indeed, the state of uncertainty regarding true reference property values
can be shown to be a limiting factor in the uncertainty of measurements made
with DSC. NIST has certified the temperatures and enthalpies of fusion of
two new Standard Reference Materials, SRMs 2234 and 2235, in order to help
alleviate some of the difficulty.