The obstruction factor in size-exclusion chromatography. 2. The interparticle, intraparticle, and total obstruction...

"Obstruction factor" is a generic rubric under which are usually gathered the interparticle, intraparticle, stationary phase, and total obstruction factors, γ(e), γ(p), γ(s), and γ(t), respectively. These, in turn, affect longitudinal diffusion and stationary, mobile phase, and stagnant mobile phase mass transfer. We conclude here our investigation into the various obstruction factors operative in size-exclusion chromatography (SEC). Stop-flow experiments were employed to determine either the interparticle (for analytes with K(SEC)=0) or the total (for analytes with K(SEC)>0) obstruction factor, and these results were combined with those from variable-flow-rate experiments which provided the intraparticle obstruction factor. Because of minimal enthalpic interactions between the analytes and stationary phase, in SEC γ(s)≈0, which allows for isolation of the other obstruction factors. A relationship between γ(t), γ(e), and γ(p) was proposed for SEC, based on previous independent work and dependent upon the various column porosities. This relationship was extended to hydrodynamic chromatography, a technique in which, ideally, both γ(s) and γ(p) are equal to zero.