This work shows buffer choice can drastically affect protein adsorption. We compared the adsorption kinetics and secondary structural evolution of BSA, IgG, fibrinogen and lysozyme on a Ge surface, buffered in PBS and Tris-HCl at pH 7.4, using ATR/FTIR. The adsorption behavior of the four proteins all undergo a short period of rapid initial adsorption with larger secondary structural changes, followed by a long period of quasi-linear adsorption. For BSA, IgG and fibrinogen, PBS buffer depressed the adsorption in the second linear kinetic region compared with Tris-HCl buffer, whereas no such effect was observed upon lysozyme adsorption. The effect of phosphate ions on protein adsorption depends on the net charge of the protein. The distribution of two dominant phosphate ion species (H₂PO₄^- and HPO₄^2-) in the adsorbed layers can vary with the protein, as well as with time. This may be related to the protein secondary structural changes upon adsorption.