Diazinon is a thiophosphoric acid ester which was used to control cockroaches, fleas, and silverfish in residential buildings. Diazinon is considered to be toxic for vertebrates causing a number of observed symptoms such as convulsions, headaches, and vomiting. Diazinon was was outlawed for residential use in the U.S. in 2004, but can be used in agricultural industries. There is a lot of interest in analyzing diazinon: it was analyzed in an analysis of acidic compounds by the EURL (European Union Reference Library) using QuEChERS methodology. Primesep 100 and Obelisc R were used to separate diazinon with unique selectivity. Method is LC/MS compatible and can be replicated for dozens of pesticides.