Stability of iron(III) complexes used as contrast agents in magnetic resonance imaging

Abstract Conditional constants at pH 7.4 are calculated for the iron(III) complexes of diethylenetrinitrilopentaacetic acid, trans -1,2-cyclohexylenedinitrilotetraacetic acid, triethylenetetranitrilohexaacetic acid and ethylenediiminobis[(2-hydroxypentyl) acetic acid]. The relationship between these constants and the stability which has previously been observed experimentally is discussed with regard to the possible formation of iron hydroxide and iron phosphate.