Effect of Thermal Treatment During the Preparation of Aluminum Hydroxide Adjuvant on the Protein Adsorption Capacity During Aging

Six aluminum hydroxide adjuvants, poorly crystalline aluminum oxyhydroxide (AlOOH) were prepared using different thermal treatments of amorphous aluminum hydroxide (Al(OH)3) in an effort to increase the protein adsorption capacity. All of the adjuvants initially exhibited a higher protein adsorption capacity. However, the protein adsorption capacity decreased during aging at room temperature. X-ray and differential centrifugal sedimentation analysis revealed that complete dehydration of amorphous aluminum hydroxide to aluminum oxyhydroxide is required to produce a stable adjuvant. Any residual amorphous aluminum hydroxide will spontaneously transform to crystalline aluminum hydroxide during aging at room temperature. Since crystalline aluminum hydroxide has a small surface area, the protein adsorption capacity of adjuvants containing amorphous aluminum hydroxide decreased by 30-40% when stored for 6 months at room temperature.