The obstruction factor in size-exclusion chromatography. 1. The intraparticle obstruction factor

We report the first of a series of studies on the obstruction factor γ in size-exclusion chromatography (SEC). Here, using narrow dispersity polymer standards we examine how the intraparticle obstruction factor γp depends individually on a number of analyte properties, column characteristics, and user-defined parameters. Far from being constant, γp is seen to vary with analyte molar mass and solvent, as well as with the pore size and particle size of the column packing material, sometimes in seemingly counterintuitive manner. Over the limited temperature range accessible to our equipment, however, no statistically significant change in γp with temperature was discovered. The results presented should be applicable to forms of packed column chromatography other than SEC. The latter technique, however, presents a convenient test bed for quantitative determination of the obstruction factor, due to minimized sorptive mass transfer and longitudinal diffusion contributions to band broadening in most forms of SEC.