CALIBRATION OF THERMAL FIELD-FLOW FRACTIONATION USING BROAD MOLECULAR-WEIGHT STANDARDS

Thermal field-flow fractionation (ThFFF) is a new elution-based separation method for determining molecular weight distributions of polymers. Calibration can be achieved using monodisperse standards of the specific polymer of interest. In order to expand the range of polymer types for which absolute molecular weight data can be obtained using ThFFF a calibration procedure has been developed and tested which uses only broad molecular weight polymer samples. The method requires two polydisperse molecular weight standards of the required polymer whose average molecular weight (normally M(w)BAR) is measured by an independent method (e.g. light scattering). From the average molecular weight data and the ThFFF elution pattern (fractogram) the required calibration constants can be calculated. The method has been tested using the polystyrene-tetrahydrofuran system and gave satisfactory results when checked against a series of monodisperse polystyrene standards. This calibration approach should expand the applicability of ThFFF to include a wide range of polymer types.