Studies in sedimentation field-flow fractionation.

摘要

Studies in sedimentation field-flow fractionation (SdFFF) are presented in this dissertation. To improve the accuracy in the characterization of colloidal materials by SdFFF, the effects of particle-wall interaction were investigated and calibration procedures were established to correct these effects.; A conventional SdFFF was modified with a heating system for high temperature studies. The elevation of temperature led to an improvement in separation resolution or an enhancement in separation speed. The experimental evidence supports the nonequilibrium theory for normal mode of FFF. Another study carried out by the heated SdFFF system was the effect of carrier viscosity on near-wall hydrodynamic lift force, a dominant lift force in steric FFF. The increase of the near-wall lift force with viscosity was generally observed and empirical expressions were derived.; A multiangle laser light scattering (MALLS) detector was coupled to a standard SdFFF system to streamline steric FFF analysis. This method requires no additional runs of size standards or further experiments of collected fractions. The particle diameters obtained were acceptable by scanning electron microscopic examinations and/or consistent with polystyrene standard analysis. The coupling of MALLS to SdFFF was also employed to defeat steric inversion, a major problem encountered when FFF is applied to polydisperse samples, for which small (normal mode) and large (steric mode) particles coelute. The binary detection method was developed upon the basis that the utilized scattering ratio of a steric particle tends to be greater than that of its normal-mode partner. The method was tested and the limitations were discussed. The application of the method to the industrial samples was reported. A computer program was developed to process the FFF-MALLS data.