ABSTRACTThe technique of inductively coupled Plasma-Atomic Emission Spectroscopy(ICP) has been used for determining the equilibrium constants of organophosphorus extractants in liquid-liquid extraction systems. The 213.618am first order atomic emission line of phosphorus was monitored to determine the equilibrium constants. The relevant equilibrium constants of bis(2,4,4-trimethylpentyl)phosphinic acid, bis(2- ethylhexyl)phosphoric acid, diphenylphosphinic acid, trioctylphosphine oxide and tri-n-butylphosphate have been determined in this manner. It has been demonstrated for the first time that the equilibrium constants for liquid-liquid extractants can be determined in a facile manner using ICP.