text: The extractive capabilities of DEHPA can be increased through synergistic effects by the addition of other organophosphorus compounds.  Tributyl phosphate is often used, as well as dibutyl-, diamyl-, and dihexylphosphonates.  The synergistic effects are thought to occur by the addition of the trialkylphosphate to the uranyl-DEHPA complex by hydrogen bonding.  The synergistic additive may also react with the DEHPA, competing with the uranyl extraction, resulting in a decrease in extraction efficiency past a concentration specific to the compound.