| Summary: | High performance liquid chromatography (HPLC) has been reported as a means of demonstrating the multicomponent nature of <SUP>99m</SUP>Tc radiopharmaceuticals. HPLC has not, however, been widely reported as a satisfactory technique for measuring the radiochemical purity (RCP) of <SUP>99m</SUP>Tc radiopharmaceuticals. Inadequate techniques based on thin-layer and paper chromatography are in widespread use for this purpose. The aim of the work described in this thesis was therefore to carry out a scientific investigation to establish if quantitative HPLC is a technique that can be used to measure the RCP of <SUP>00m</SUP>Tc radiopharmaceuticals. An on-line radiation detector was developed and evaluated. This was constructed from a length of column outlet tubing positioned inside the well or across the face of a sodium iodide crystal scintillation detector. The different configurations of tubing and crystal were used to create different sensitivities of detection. Chromatograms were recorded with either a counter-ratemeter/printer system or a computer-based multichannel analyser. At 6,000 counts per second, the highest count-rate encountered in the course of the work, the loss due to dead-time in the multichannel analyser was satisfactorily low at 0.5%. For successful measurement of RCP, none of the radiolabelled species in a radiopharmaceutical must be retained on the HPLC column and thereby escape detection. A technique for measuring recovery from the column was therefore developed. This involved injecting the sample onto the column with a loop-valve injector, collecting the eluate and measuring the count-rate from it relative to the count-rate from an accurately pipetted sample of the radiopharmaceutical.
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