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Hydrodynamic chromatography (HDC) has experienced a resurgence in recent years for particle and polymer characterization, principally because of its coupling to a multiplicity of physical detection methods. When coupled to light scattering (both multiangle static and quasi-elastic), viscometric, and refractometric detectors, HDC can determine the molar mass, size, shape, and structure of colloidal analytes continuously and as a function of one another, all in a single analysis. In so doing, it exposes the analytes to less shear force (and, hence, less potential for flow-induced degradation) than in, for instance, size-exclusion chromatography. In this review, we discuss the fundamental chromatographic underpinnings of this technique in terms of retention, band broadening, and resolution, and we describe the power of multidetector HDC with examples from the recent literature.

Chemical and physical detectors characterize the distributions of macromolecular parameters that have a critical effect on the end product.S ynthesizing polymers is not as exact a science as we would like it to be. Natural syntheses and even well-controlled laboratory syntheses often yield macromolecules that vary in length, molar mass, branching, chemical composition, and other properties. Characterizing these properties and their distributions is important because of their critical effect on end-use structure-property relations and, hence, on the end product itself. The most commonly studied properties are the molar mass averages (M n , M w , M z , etc.) and the molar mass distribution (MMD). Various processing characteristics of macromolecules can be related to the individual averages, for example, flow properties and brittleness (related to M n ) and flex life and stiffness (related to M z ). Similarly, properties such as tensile strength and abrasion resistance tend to increase as MMD narrows, and properties such as elongation and yield strength tend to increase as MMD broadens.During the past four decades, size-exclusion chromatography (SEC) has been established as the premier method for characterizing M averages and the distribution of natural and

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A detailed quantitative description of particle size, shape, and their distributions is essential for understanding and optimization of the solid-, solution-, and melt-state properties of materials. Here, we employ quadruple-detector hydrodynamic chromatography (HDC) with multi-angle static light scattering, quasi-elastic light scattering, differential viscometry, and differential refractometry detection as a method for characterizing three important physical properties of materials, namely the molar mass, size, and shape of a polydisperse, non-spherical colloidal silica sample. These properties and their distributions were measured continuously across the HDC elution profile of the sample. By combining information from the various parameters determined, we were also able to obtain quantitative knowledge regarding the compactness or denseness of the sample. The applicability of multi-detector HDC to characterize polydisperse, non-spherical analytes was shown to be rapid, accurate, and precise. An advantage over traditional characterization methods is the ability of multi-detector HDC to determine particle size, shape, compactness, and their distributions simultaneously in a single analysis.