Calorimetric crystallization method for evaluation of monomer purity

A method for on-line evaluation of monomer formulation purity comprising the steps of:

• a) raising the temperature of the monomer formulation having a defined melting point to a first elevated temperature at least 20° C. above a preset melting point for a selected monomer formulation;
• b) cooling the monomer formulation at a controlled cooling rate in the range from about 0.5 to 50° C. per minute;
• c) measuring at least one critical property selected from the group consisting of a) crystallization peak temperature at the onset of crystallization, b) an area under the crystallization peak, which represents the heat or enthalpy of crystallization, ΔHc and combinations thereof;
• d) comparing the at least one of the selected critical properties measures relative to such properties for standard setting monomer formulations;
• and
• e) estimating the purity of the sample monomer formulation, wherein lower values for the temperature of the crystallization peak temperature or a smaller crystallization peak area, each relative to the standard values for corresponding standard setting monomer formulation, indicates a higher presence of impurities relative to the standard setting monomer formulation.