Recent developments in the analysis of technetium-99

Analysis of 99Tc using an extraction chromatographic resin to isolate technetium from other elements, followed by liquid scintillation counting has become common worldwide. The method is robust and has been applied to a wide variety of matrix types. Recently, high biases have been reported when samples with high levels of naturally occurring uranium were analyzed. The problem was traced to incomplete decontamination of the technetium fraction from 234Th (daughter of 238U) present in the samples. A variety of protocol modifications to the load and rinse solutions were attempted in order to improve the decontamination of the technetium fraction. It was determined that complexing agents were required to remove thorium from the column. Oxalate solutions provided better decontamination than nitric acid and hydrochloric acid solutions alone for samples with low levels of natural uranium. However, fluoride was found to be necessary to ensure adequate decontamination from samples containing up to 44 Bq of natural uranium. (author)