The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9 μm fully porous Titan-C18 particles II – Analysis of biomolecules

• The mass transfer kinetics of biomolecules are measured for the new 120 Å 1.9 μm Titan-C18.
• Increasing the pore size from 80 to 120 Å markedly improve the analysis of small proteins.
• Only measurable gain in column efficiency are observed for peptides such as bradykinin.
• The mass transfer of insulin is controlled by it absorption kinetics into the Titan particles.
• The intensity of intra-particle diffusivity is not always correlated to the average pore size.

The kinetic performances of 3.0 × 100 mm columns packed with 1.9 μm Titan-C18 particles with average mesopore sizes of 80 Å and 120 Å were investigated quantitatively for the analysis of biomolecules. Large mesopores are expected to speed up the rate of diffusivity of high-molecular-weight compounds across the stationary phase and to generate higher plate counts at high velocities. The mass transfer mechanism of bradykinin acetate salt (1060 Da) and insulin (5733 Da) was determined over a range of flow rates from 0.025 to 1.0 mL/min. The pore diffusivities of these two biomolecules were accurately measured from the peak parking method.Even though the gain in column efficiency was not found significant for small molecules such as valerophenone (162 Da), enlarging the average pore size from 80 to 120 Å induces a measurable diminution of the reduced plate height, h, of bradykinin (from 17 to 11 or −35% at a reduced velocity of 50) and a significant reduction for insulin (from 43 to 12 or −72% at a reduced velocity of 90). Remarkably, while the increase of the column efficiency for bradykinin is consistent with a faster diffusivity of bradykinin across the 120 Å Titan-C18 particles, the higher column efficiencies measured for insulin are mostly due to a faster absorption kinetics into the 120 Å than that into the 80 Å Titan-C18 particles. This result is supported by the fact that the effective pore diffusivity of insulin is even slightly smaller across the 120 Å than that across the 80 Å 1.9 μm Titan-C18 particles.