Malathion is the most widely used organophosphate pesticide used in the U.S.. Used heavily in residential landscaping and in public recreation areas, malathion is often used for fruit fly and mosquito eradication. While not considered toxic to humans, malathion metabolizes to a far more toxic malaoxon. The EURL included malathion as a target pesticide for the EUPT-CF9. Obelisc R was used to retain malathion and separate it from impurities. 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 malathion and other organophosphate insecticides.