This work presents a study on the interfacial activity of amoxicillin in aqueous systems containing polyethylene glycol (PEG). The results showed that aqueous systems containing different amounts of PEG and amoxicillin reach promptly the chemical equilibrium, displaying a small variation in surface tension over the time. However, the PEG concentration increasing causes a surface tension reduction, which indicates increasing the surface-active component amount on the interface. It was not identified the occurrence of critical micelle concentration for the amoxicillin within the concentration range of this study. Data must be useful for design and operation of processes involving the amoxicillin extraction in two phase aqueous systems containing polyethylene glycol.
