| Particle size, shape, and their distributions directly influence a variety of processing and end-use properties related to packing, mixing, and transport of powders, solutions, and suspensions. Many of the techniques currently employed for particle size characterization have found limited applicability for broadly polydisperse and/or non-spherical particles. We have attempted to overcome many of the limitations of these techniques through the systematic development of multi-detector hydrodynamic chromatography (HDC) methodology for the characterization of mono- and polydisperse spherical and non-spherical particles and ultra-high molar mass polymers.;Initially, HDC with multi-angle static light scattering (MALS), quasi-elastic light scattering (QELS), differential viscometry (VISC), and differential refractometry (DRI) detection, was used to characterize the size, shape, and compactness of monodisperse spherical polystyrene and poly(methyl methacrylate) particle standards. From these analyses, we were able to measure three colloidal radii, and also to determine the shape and structure or compactness of the particles. Once the HDC/MALS/QELS/VISC/DRI technique was proven successful for characterizing monodisperse spherical particles, our analytical approach was refined to include spherical particles polydisperse in size, compactness, and chemistry. Analysis of these polydisperse particles demonstrated the robustness of the HDC method, in which the multiplicity of detection methods employed helps compensate for the inherently low chromatographic resolution of the separation method.;The next step in the sequential development of multi-detector HDC methodology was to examine non-spherical particles. A polydisperse prolate ellipsoidal silica particle was successfully characterized based on molar mass, three colloidal radii, and their distributions. The synergetic combination of size information obtained through the use of multiple physical detectors provided information on particle shape and compactness across the HDC elution profile, through the application of various dimensionless size ratios.;A collaboration with Inovatia Laboratories LLC., then allowed us to extend the HDC method to the study of nanoparticles that had been shown to be polydisperse in both size and shape by transmission electron microscopy (TEM). These analyses confirmed the accuracy and precision of the HDC technique, which provided a more complete structural picture of the nanoparticles than did TEM, in a fraction of the time needed for the latter.;We then evaluated the ability of multi-detector HDC to analyze irregular-shaped objects by analyzing a colloidal assembly of silica particles, with a shape similar to that of a string-of-pearls. Two different separation techniques, HDC and size-exclusion chromatography (SEC), were used to characterize this sample. The string-of-pearls was shown to degrade during SEC analysis, but not during HDC analysis. The multiple detection methods employed allowed us to expand the type of information obtained in previous studies to include the observation that the sample contained "strings" varying in degree of polymerization, as well as individual "pearls.";Lastly we used, HDC to study ultra-high molar mass polymers which had been shown to experience on-column, flow-induced degradation by SEC. Multi-detector HDC was able to determine the molar mass and size of the ultra-high molar mass polysaccharide alternan more accurately than SEC, in a fraction of the time.;In conclusion, multi-detector HDC has been successfully and systematically developed into a method for characterizing complex particles and ultra-high molar mass polymers based on their size, shape, and compactness. Because the multi-detector HDC technique employed instrumentation common to most macromolecular separations laboratories, it shows great promise in the areas of particle and polymer characterization. |
