Kinetic study of desorption of two species of bovine serum albumin from alumina during alkali elution process.

Kinetics of desorption of irreversibly adsorbed bovine serum albumin (BSA) from alumina (Al2O3) particles at various surface coverages (theta) was studied in a plug-flow column by feeding 0.05 M NaOH solution. The desorption curve obtained by plotting the logarithm of the amount of residual BSA against elution time was analyzed by using an integrated model that describes two simultaneous first-order processes. At each of theta, except for an initial lag time, the curve of BSA desorption could be reduced to the sum of two independent and simultaneous first-order processes occurring at different rates. The desorption rate constant (k(f)) for a faster-desorbing BSA (BSA(f)) was influenced by theta, especially above 0.7. On the other hand, the rate constant (k(s)) for a slower-desorbing BSA (BSA(s)) was fairly constant irrespective of theta and approximately 25- to 100-fold lower than k(f). The amount of BSA(f) estimated was proportional to theta, whereas that of BSA(s) reached a plateau value corresponding to 12.8% of saturation amount at theta above 0.42.