Phosphamidon is an organophosphate insecticide highly toxic to mammals and classified by the World Health Organization to be extremely hazardous (Ia), with an oral lethal dose of less than 5mg/kg of bodyweight. The EURL (European Union Reference Laboratory) included phosphamidon as a target pesticide for the EUPT-CF9. Primesep 100 and Obelisc R were used to retain phosphamidon and separate it from impurities. Primesep 100 contains embedded acidic ion-pairing groups and Obelisc R contains embedded ionic and hydrophobic groups which can assist in fine tuning separations. Method is LC/MS compatible and can be used as a general approach for analyzing phosphamidon, other organophosphate insecticides, and dozens of other pesticides.