Estimation of the “hydrophobic reactivity” of SDS micelles by the use of BPh4− anions

► We present a new expression of the degree of condensation of Na+ on SDS micelles. ► Quantitative description of the hydrophobic affinity of SDS to BPh4- anions. ► Detection of incorporated BPh4- ions by high precision conductivity. ► Conductivity of SDS-NaBPh4 is modelled according to Onsager-Kim-MSA theory. ► Micellization, ionic condensation and absorption are interdependent processes.