Synthesis and chromatographic characterization of [Tc-99m]technetium-humic acid species

Abstract

A natural moor soil humic acid (HA) was labeled with Tc-99m via reduction of pertechnetate with stannous chloride. The humic acid species obtained were characterized by thin layer chromatography (TLC), gel permeation chromatography (GPC), sequential chromatographic analysis (SCA), paper electrophoresis and micropore filtration. Labeling was found to take place in all ranges of molecular weight. Due to the complex humic acid composition and the formation of hydroxo species the labeling yields strongly depend on the separation conditions, ranging from 42% to 80%. The pH-dependent distribution of mobile and immobile species was determined by SCA for HTcO 4 , HA and for Tc-HA-species obtained after labeling. Geochemically relevant properties of HA remain unchanged after the labeling procedure, only macroscopic amounts of the reducing agent Sn 2+ give rise to a shift to lower molecular weight species.