HPLC methods are provided to separate and detect morphinone, morphine, and dihydromorphine in the presence of hydromorphone. The isocratic HPLC methods employ ion-pair solute-solute ion-exchange mobile phase techniques in reversed phase chromatography. Method conditions in the disclosure provide separation and quantification of opioid pharmacophores in accordance with federal guidelines for obtaining resolution between analytes R≧2.0; tailing factor T≦2.0, capacity factor 2