Measurement and simulation of tailing zones of a cationic dye in analytical-scale reversed phase chromatography

A quantitative physical description of tailing is reported here for analytical-scale reversed phase chromatography with Type B silica. Simulations of experimental chromatograms for a cationic dye, 1,1′-didodecyl-3,3,3′3′-tetramethylindocarbocyanine perchlorate (DiI) were performed as a function of DiI concentration and flow rate, revealing nonlinear tailing due to a bi-Langmuir adsorption isotherm. The strong site comprises less than 0.1% of the residual silanols, the desorption rate constant of DiI from this type of site is (85±8 ms)−1, and the free energy of the silanophilic interaction is 16 kJ/mol, indicating hydrogen bonding or another strong electrostatic interaction.