Determination of pertechnetate in radiopharmaceuticals by high-pressure liquid thin-layer and paper chromatography

Abstract

Pertevhnetate ion, considered a common impurity, is usually determined in technetium pharmaceuticals by paper or thin-layer chromotography. The results are often sensitive to variations in procedure, particularly with relatively unstable agents such as pyrophosphate. We have developed a method for determining partechnetate by high pressure liquid chromatography (HPLC) and compared it with previous methods, which include a commercially available kit. When applied to a variety of agents in clinical use (technetium pyrophosphate, methylene diphosphonate, glucoheptonate, diethylenetriaminepentaacetate) HPLC indicated lower concentrations of pertechnetate than did conventional methods. In fact, though pertechnetate was demonstrated in tin-free electrolytic preparations or in tin-labelled preparations' which had been exposed to air, HPLC showed no pertechnetate in fresh preparations containing excess tin. We conclude that: (1) the reaction of Sn(II)with pertechnetate is rapid enough under usual labelling conditions that the two species do not coexist, (2) when pertechnetate is found in preparation containing excess Sn(II) it is usually an artifact of the chromatographic procedure, (3) by careful choice of paper or thin-layer method (which must be verified for each formulation) this artifact can often be rendered neglible and (4) HPLC is useful as a reference method for determining pertechnetate in radiopharmaceuticals.