High performance liquid chromatography for the simultaneous analysis of penicillin residues in beef and milk using ion-paired extraction and binary water-acetonitrile mixture

► Polar compounds like penicillins can be extracted in polar solvent using binary water-acetonitrile. ► The additive of salting-out agent increased the polarity of binary water-acetonitrile. ► The separated phase occurred in a high polarity compared to acetonitrile alone. ► The separated phase can be directly injected into HPLC system without any treatment. ► The proposed method was shown to be of high potential extraction and preconcentration method for penicillin analysis.