The adsorption behavior of bovine serum albumin BSA on a silica surface can be significantly affected by the pH of the solution. Quartz crystal microbalance QCM is a sensitive technique used to study the adsorption and desorption processes of proteins on various surfaces, including silica.The effect of pH on BSA adsorption on silica surfaces can be explained by considering the isoelectric point pI of BSA and the surface charge of silica. The pI of BSA is approximately 4.7, which means that at pH values below 4.7, BSA carries a net positive charge, while at pH values above 4.7, it carries a net negative charge. Silica surfaces are negatively charged at neutral and basic pH values and become less negatively charged as the pH decreases.1. At low pH values below the pI of BSA , BSA carries a net positive charge and can interact with the negatively charged silica surface through electrostatic attraction. This results in increased adsorption of BSA on the silica surface.2. At the pI of BSA pH 4.7 , BSA has no net charge, and the electrostatic interactions between BSA and the silica surface are minimized. However, other forces, such as van der Waals forces and hydrogen bonding, can still contribute to BSA adsorption.3. At high pH values above the pI of BSA , both BSA and the silica surface carry a net negative charge, leading to electrostatic repulsion between the protein and the surface. This results in decreased adsorption of BSA on the silica surface.In summary, the adsorption behavior of BSA on a silica surface using QCM measurement technique is highly dependent on the pH of the solution. At low pH values, BSA adsorption is enhanced due to electrostatic attraction, while at high pH values, adsorption is reduced due to electrostatic repulsion. At the pI of BSA, other forces such as van der Waals forces and hydrogen bonding may contribute to the adsorption process.