Experimental investigation of the retention factor dependency of eddy dispersion in packed bed columns and relation to knox's empirical model parameters

Measurement and modelling of the intra-particle diffusion and b-term in reversed-phase liquid chromatography

“…( 31). Similarly high b-term values at k"= 35-40 have been reported previously [10]. The obtained b-term values are consistently larger for the C8-80 Å and C18-300 Å column over the entire range of k"-values, in comparison with the C18-80 Å column, which can be attributed to the larger enrichment in organic modifier in the stationary phase layer observed for these two columns (see Figure 4), which in turn leads to a higher average intra-particle diffusion.…”

“…The models for intra-particle diffusion, Eqs. (10)(11), introduced in the theory section are based on the definition (and hence experimental determination) of four distinct fractions (f1, f2, f3, f4), whose definition partly depends on whether the zone filled with 100% organic modifier extends outside the alkyl chain layer (regime 1) or not (regime 2).…”

“…Eqs. (10)(11). The values of the diffusion coefficients in the different mobile phases (Dm) and in the layer enriched with 100% ACN (D100% org) were calculated using the correlations in [41].…”

“…Similar observations can be made for the partition-based model in Eq. (10), which only incorporates an obstruction factor for the diffusion in the retained state (termed 3 in Eq. ( 10)).…”

“…Making abstraction of the contribution of the extra-column volume, these mainly include eddy dispersion (the so-called a-term in plate height models), longitudinal diffusion (the b-term) and mass transfer resistance due to the velocity differences between stagnant molecules inside the mesopores and molecules moving along with the mobile phase occupying the interstitial volume (the c-term). In recent years, experimental protocols have been developed to assess the individual contributions to band broadening more accurately, enabling a more indepth understanding of the mechanisms underlying band broadening [7][8][9][10][11][12][13]. One such mechanism that has been demonstrated to influence the a-, b-and c-term, is intra-particle diffusion [14,15].…”