Determination of the protonation constants of gadolinium(III) diethyltriaminepentaacetic acid by solvent extraction and ICP-AES

摘要

The first and second protonation constant (log#beta#_(111), log#beta#_(121) of the metal-ligand complex Gadolinium(III)-diethyltriamine-pentaacetic acid (DTPA) have been determined to be 2.27 and 1.52 at 25 deg C and I = 0.1. A technique in which the three complexes (H_2Gd-DTPA, HGd-DTPA~(-1), Gd-DTPA~(-2)) are separated according to their relative polarity is utilized. An inductively coupled plasma-atomic emission spectrometer (ICP-AES) is used to determine the relative concentrations of each species by monitoring the gadolinium concentration.