Optimal aluminum/zirconium: Protein interactions for predicting antiperspirant efficacy using zeta potential measurements.

The interactions between commercial antiperspirant (AP) salts (aluminum chlorohydrate (ACH), activated ACH, aluminum sesquichlorohydrate (ASCH), zirconium aluminum glycine (ZAG), activated ZAG), pure aluminum polyoxocations (Al-13-mer, Al-30-mer), and the zirconium(IV)-glycine complex [Zr-6 (O)(4) (OH)(4) (H2O)(8) (Gly)(8)](12+) (CP-2 or ZG) with Bovine serum albumin (BSA) were studied using zeta potential and turbidity measurements. The maximal turbidity, which revealed the optimal interactions between protein and metal salts, for all protein-metal salt samples was observed at the isoelectric point (IEP), where the zeta potential of the solution was zero. Efficacy of AP salts was determined via three parameters: the amount of salt required to flocculate BSA to reach IEP, the turbidity of solution at the IEP, and the pH range over which the turbidity of the solution remains sufficiently high. By comparing active salt performance from this work to traditional prescreening methods, this methodology was able to provide a consistent efficacy assessment for metal actives in APs or in water treatment.