Chromatography, hydrodynamic

DA Hoagland. Unified thermodynamic model for polymer separations produced by size exclusion chromatography, hydrodynamic chromatography, and gel electrophoresis. ACS Symp Ser 635 173-188, 1996. 

Surface exclusion chromatography (hydrodynamic exclusion chromatography) has been developed for rigid particle size determinations. This technique has been shown to be effieient for size separation of proteins and latexes. It uses a non-porous packing as a stationary phase. 

MOLECULAR WEIGHT SEPARATION OF MACROMOLECULES BY HYDRODYNAMIC CHROMATOGRAPHY... 

Hydrodynamic chromatography (HdC) is a relatively new technique, especially in molecular weight separation. It was first investigated in 1969 by DiMarzio and Guttman (1,2) and was called separation by flow (3,4). Small started calling it hydrodynamic chromatography in 1974 (5). The application of this technique was first concerned with the separation of particle size. Prud homme applied it to the molecular weight separation of macromolecules in 1982 (6). 

II. OPEN MICROCAPILLARY TUBULAR HYDRODYNAMIC CHROMATOGRAPHY (OTHdC)... 

The major advantage of the capillary hydrodynamic chromatography is that the mobile phase does not need to have similar solubility parameter as the sample and packing material. (In SEC, nonsize exclusion effects may be observed if the solubility parameter of the sample, packing material, or mobile phase is considerably different.) Therefore, the hydrodynamic size of polymers can be studied in a 0 solvent and even in a solvent that is not compatible with any currently available SEC packing material (9). Figure 22.4 is an example of polystyrene separation in both THF and diethyl malonate. Diethyl malonate is the 0 solvent of polystyrene at 31-36 C. 

The HdC calibration curves of different particle sizes, as shown in Fig. 22.12 (30), are similar to the calibration curves of different pore size columns the separation ranges of MW due to hydrodynamic chromatography depend on particle size. The larger the particle size, the higher the MW ranges. Stegeman et al. (30) proposed that a smooth calibration curve may be achieved by proper ratio of the particle diameter to the pore diameter. 

SEC, size exclusion chromatography OTHdC, open tubular hydrodynamic chromatography PCHdC, packed column hydrodynamic chromatography ThFFF, thermal field flow fractionation. 

Column efficiency (number of theoretical plates) As in batch chromatography, one needs to determine the efficiency of the column in order to evaluate the dispersion of the fronts due to hydrodynamics dispersion or kinetics limitations. The relationship of N proportional to L can be expressed in terms of the equation for height equivalent to a theoretical plate (HETP) as ... 

Advanced computational models are also developed to understand the formation of polymer microstructure and polymer morphology. Nonuniform compositional distribution in olefin copolymers can affect the chain solubility of highly crystalline polymers. When such compositional nonuniformity is present, hydrodynamic volume distribution measured by size exclusion chromatography does not match the exact copolymer molecular weight distribution. Therefore, it is necessary to calculate the hydrodynamic volume distribution from a copolymer kinetic model and to relate it to the copolymer molecular weight distribution. The finite molecular weight moment techniques that were developed for free radical homo- and co-polymerization processes can be used for such calculations [1,14,15]. 

The publications on a technique of particle size measurement called hydrodynamic chromatography (HDC) by Hamish Small, ... 

Size exclusion chromatography (SEC) separates molecules of a polymer sample on the basis of hydrodynamic volume. When the chromatograph is equipped only with a concentration-sensitive detector, i.e. conventional SEC, a molecular weight distribution (MWD) can be obtained from the chromatogram only through use of a calibration function relating molecular weight and elution volume V (2). 

D. Recommendations. Cross-Fractionation using Orthogonal Chromatography has high potential in the analysis of complex polymers and even polymer latices (with Hydrodynamic Chromatography). Multi-detector analysis, particularly utilizing spectrofluorometry, should be very useful in developing the technique. 

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