Rapid Actinide Column Extraction Methods for Bioassay Samples

Abstract

Significant improvements have been made in extraction chromatography methods for bioassay samples in the last decade. Both single column and tandem column methods have been utilized in laboratories to analyze bioassay samples. A new, rapid separation method to assay actinides in urine samples has been developed at the Westinghouse Savannah River Site (SRS) that illustrates one of the newest developments that has been made in this field. This method combines some of the features of both single column and tandem column methods, utilizing two highly selective resins stacked to form a single column. The new method separates plutonium, neptunium, uranium, americium and strontium-90 from urine samples with high chemical recovery and excellent removal of matrix interferences such as thorium. Fast flow rates are achieved by using small particle size resin cartridges and a vacuum box separation system that will separate up to 24 samples at a time. The method uses calcium phosphate precipitation and stacked TEVA Resin® and TRU Resin® cartridges to separate and purify the actinides. Plutonium and neptunium are separated on TEVA Resin®, while uranium and americium are simultaneously retained and separated on TRU Resin®. Plutonium-236 tracer is used to allow simultaneous separation and measurement of both plutonium and neptunium using TEVA Resin®. Strontium-90 can also be separated on Sr Resin® by evaporating and redissolving load and rinse solutions collected from the TEVA/TRU column and separating strontium on Sr-Resin. This unique approach can be used with urine samples because iron is not present at significant levels in urine and plutonium reduction is accomplished without adding iron (II) to the sample. The advantage of this approach is that actinides can be loaded onto two separate resins in a single load step. This method offers significant advantages when a large number of actinides are analyzed, but is just one of the several different extraction chromatography methods now available for bioassay samples.