Determination of the rate control step of purin and pyrimidine bases adsorption on cobalt(II)–CDAE-sporopollenin

In this work, adsorption kinetics of nucleic acid bases and nucleosides as ligands on cobalt(II)–carboxylated diaminoethyl sporopollenin (CDAE-sporopollenin) have been performed using continuous column runs. Adsorption rate measurements were carried out by using a UV-Vis spectrophotometer, and rate control step of the adsorption process was determined. The adsorption of nucleic acid bases and nucleosides from solutions of different initial concentrations onto resin was measured as a function of time at 25 °C. The results show that type of ligand has a great effect on ligand adsorption behaviour. External ligand concentrations play a significant role on adsorption rate of nucleic acid bases. The homogeneous diffusion model (HDM) is applied to the experimental breakthrough data. In all of the concentration range of adenine and uracil (nucleic acid bases), the graphs of −ln[1−U(α)] versus t were a straight line, which suggests that fractional attainment of equilibrium adsorption under film diffusion control is observed. On the contrary, adenosine and uridin (nucleosides), the graphs were not a straight line and have underwent adsorption under particle diffusion control.