Quantitative particle size and molecular weight determinations by time-delayed exponential force-field sedimentation field flow fractionation (TDE-SFFF) can currently be carried out in 15–20 min using automated apparatus with force fields of up to 50,000 gravities. New resolution parameters provide a common basis for comparing the ability of the commonly used separation methods for particle size analyses. These parameters show that TDE-SFFF has a 5–10 fold and 10–50 fold greater specific resolution than size-exclusion chromatography (SEC) and packed column or capillary hydrodynamic chromatography (HDC), respectively. Because of high resolving power and other characteristics, TDE-SFFF provides superior accuracy in particle size distribution analyses relative to these other separation methods, as confirmed by direct comparisons with typical literature data for a range of particulate samples. TDE-SFFF also has similar advantages over conventional non-chromatographic methods. For example, SFFF exhibits approximately the same resolving power as disc centrifugation but a much wider dynamic range of particle diameter separation in a single analysis.SFFF provides higher separation resolution than SEC and HDC because of intrinsic differences in retention mechanisms. These latter chromatographic methods separate species by size-exclusion effects —peaks elute prior to the mobile phase solvent —therefore, HDC and SEC are basically limited by available fractionation volume. On the other hand, SFFF exhibits true retention like the affinity liquid chromatography (LC) methods —peaks elute after the unretained mobile phase solvent. In contrast to SEC and HDC, but like LC, TDE-SFFF has the potential for very high peak capacity.
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Mar 1, 1982
Stig Allenmark + 2
