An Application of Paper Electrophoresis to the Examination of Completeness of Reaction and Purification in the Synthesis of Radioactive Compounds

Abstract

THE usefulness of [(carboxymethylimino)bis(ethyl-enenitrilo)]tetraacetic acid (DTPA) in correcting iron chlorosis induced by lime in plants has been well documented^1,2. DTPA labelled with carbon-14 was required to facilitate studies concerning the metabolism of the compound in plants ; accordingly, the synthesis was undertaken. The method used involved an alkylation of diethylenetriamine (DET) with bromoacetic acid. In preliminary work, it became evident that the usual methods available for determining chelating materials, such as titration with calcium ion in the presence of oxalate or sprays with a nickel-dimethylglyoxime reagent, would not be satisfactory for following the course of the reaction. These reagents will neither indicate the distribution nor detect all the compounds arising as a result of incomplete alkylation. Paper electrophoresis was found to be a very powerful tool for the delineation of all the compounds formed in the reaction.