Treatment of aluminium hydroxide adjuvant to optimize the adsorption of basic proteins.

Aluminium hydroxide adjuvant has an isoelectric point (i.e.p.) of ca 11 and is a good adsorbent for acidic proteins due to the contribution of electrostatic attractive forces. However, electrostatic repulsive forces reduce its ability to adsorb basic proteins. Pretreatment of aluminium hydroxide adjuvant with carefully selected concentrations of phosphate anion reduces the positive surface charge which exists at pH 7.4. Treatment with higher concentrations of phosphate anion produces a negative surface charge. The adsorption of lysozyme (i.e.p = 11.1) was found to be directly related to the concentration of phosphate anion used to pretreat the aluminium hydroxide adjuvant.