FINGERPRINTING OF COSMETIC FORMULATIONS BY DYNAMIC ELECTROKINETIC ANDPERMEABILITY ANALYSIS .1. SHAMPOOS

The interaction of shampoos with human hair was studied by employing a n instrument that can perform simultaneous analysis of electrokinetic parameters (streaming potential and conductivity) and the permeability of fiber plugs. The experimental protocol included the measurements o f a newly formed hair plug and its treatment with a solution of a sham poo or a model compound, followed by rinsing with the test solution. E lectrokinetic and permeability data collected during the rinsing stage allowed derailed analysis of the dynamics of change in the ionic char acter of hair surface produced by the adsorption of a conditioning age nt. The variation in the thickness of surface deposits could be evalua ted from the flow-rate measurements. Several types of formulations wer e analyzed, such as nonconditioning shampoos based on anionic surfacta nts, and conditioning systems containing cationic polymers, cationic s urfactants, and silicone oils. it is shown chat a combination of exper imental traces, including streaming and zeta potentials, conductivity, and flow race (permeability) as a function of time, is unique for eac h investigated formulation. Multiple treatments with the same formulat ion were allowed to estimate the extent of buildup of conditioning lay ers. The ability of nonconditioning compositions to remove polymer and surfactant residues was analyzed by consecutive application of condit ioning and nonconditioning formulations.