Manipulation of mass transport rates using bead-in-a-tube method.

In ultralow Pu analyses, the gold standard is thermal ionization mass spectrometry (TIMS), which requires pure sources to achieve its performance. This purity is achieved through step-wise purifications. In this work single, anion-exchange beads were trapped in the tubing to allow for dynamic solution cycling over the surface of the beads to improve the rates of metal complex uptake. Rates of Pu sorption on single ∼900 µm SIR-1200 and ∼620 µm Reillex-HPQ beads were determined for single beads trapped in a tube with syringe pump driven dynamic solution cycling over the bead, improving sorption and desorption rates. A static control was used as a comparison. Using 238Pu to enable facile activity-based measurements, rates were determined by measuring the residual Pu after contact with beads using liquid scintillation analysis (LSA) for fixed periods of time. Syringe pump driven dynamic solution cycling results in ∼5 and ∼15-fold improvements in the sorption rates for SIR-1200 and Reillex-HPQ. Impacts on desorption were also examined.

Tandem column isolation of zirconium-89 from cyclotron bombarded yttrium targets using an automated fluidic platform: Anion exchange to hydroxamate resin columns.

The development of a tandem column purification method for the preparation of high-purity 89Zr(IV) oxalate is presented. The primary column was a macroporous strongly basic anion exchange resin on styrene divinylbenzene co-polymer. The secondary column, with an internal volume of 33 µL, was packed with hydroxamate resin. A condition of inverted selectivity was developed, whereby the 89Zr eluent solution for the primary column is equivalent to the 89Zr load solution for the secondary column. The ability to transfer 89Zr from one column to the next allows two sequential column clean-up methods to be performed prior to the final elution of the 89Zr(IV) oxalate. This approach assures delivery of high purity 89Zr product and assures a 89Zr product that is eluted in a substantially smaller volume than is possible when using the traditionally-employed single hydroxamate resin column method. The tandem column purification process has been implemented into a prototype automated fluidic system. The system is configured with on-line gamma detection so column effluents can be monitored in near-real time. The automated method was tested using seven cyclotron bombarded Y foil targets. It was found that 95.1 ±â€¯1.3% of the 89Zr present in the foils was recovered in the secondary column elution fraction. Furthermore, elution peak analysis of several 89Zr elution profile radiochromatograms made possible the determination of 89Zr recovery as a function of volume; a 89Zr product volume that contains 90% of the mean secondary column elution peak can be obtained in 0.29 ±â€¯0.06 mL (representing 86 ±â€¯5% of the 89Zr activity in the target). This product volume represents a significant improvement in radionuclide product concentration over the predominant method used in the field. In addition to the reduced 89Zr product elution volume, titrations of the 89Zr product with deferoxamine mesylate salt across two preparatory methods resulted in mean effective specific activity (ESA) values of 279 and 340 T Bq·mmole-1 and mean bindable metals concentrations ([MB]) of 13.5 and 16.7 nmole·g-1. These ESA and [MB] values infer that the 89Zr(IV) oxalate product resulting from this tandem column isolation method has the highest purity reported to date.

Optimized anion exchange column isolation of zirconium-89 (89Zr) from yttrium cyclotron target: Method development and implementation on an automated fluidic platform.

Zirconium-89 (89Zr), produced by the (p, n) reaction from naturally monoisotopic yttrium (natY), is a promising positron emitting isotope for immunoPET imaging. Its long half-life of 78.4 h is sufficient for evaluating slow physiological processes. A prototype automated fluidic system, coupled to on-line and in-line detectors, has been constructed to facilitate development of new 89Zr purification methodologies. The highly reproducible reagent delivery platform and near-real time monitoring of column effluents allows for efficient method optimization. The separation of Zr from dissolved Y metal targets was evaluated using several anion exchange resins. Each resin was evaluated against its ability to quantitatively capture Zr from a load solution high in dissolved Y. The most appropriate anion exchange resin for this application was identified, and the separation method was optimized. The method is capable of a high Y decontamination factor (>105) and has been shown to remove Fe, an abundant contaminant in Y foils, from the 89Zr elution fraction. Finally, the method was evaluated using cyclotron bombarded Y foil targets; the method was shown to achieve >95% recovery of the 89Zr present in the foils. The anion exchange column method described here is intended to be the first 89Zr isolation stage in a dual-column purification process.

Hydroxamate column-based purification of zirconium-89 (89Zr) using an automated fluidic platform.

Zirconium-89 (89Zr) is a long-lived (t1/2 = 78.4h) positron-emitting isotope that is useful for positron emission tomography (PET) based diagnostic imaging using radiolabeled antibodies. Hydroxamate resin columns are predominantly used for the purification of 89Zr from cyclotron bombarded natY targets dissolved in strong HCl. 89Zr is conventionally eluted from the resin in 1M oxalic acid (H2C2O4), a complexant that is conducive to follow-on binding of 89Zr through a transchelation process to the deferoxamine siderophore. In the present study, we determined that a lower concentration of H2C2O4 eluent (0.8M) is adequate to efficiently remove 89Zr from a column containing 100mg hydroxamate resin. As a result, less buffering agents are needed to be added to the 89Zr product fraction prior to labeling. A simple automated fluidic system prototype has been developed to perform the steps required for 89Zr purification using a hydroxamate resin column (column conditioning in HCl, Y target dissolution, dissolved target solution load onto column, column washes using HCl and water, and 89Zr elution). The system performance was evaluated using several cyclotron bombarded Y targets; 89Zr product fractions demonstrated excellent chemical recoveries from these targets, with 1.0mL product volumes yielding 89±2% of the column elution peak activity and 84±2% of 89Zr recovered from the target (at EOB). These results compare favorably with previously published 89Zr product volumes and yields, despite the lower concentration of H2C2O4 eluent employed. Transchelation of resulting 89Zr product fractions was performed to assess product quality. The effective specific activity (ESA) ranged between 44(7) and 109(22) TBq·mmole-1, while the bindable metals concentration, a metric introduced for assessing and comparing product purity, ranged between 43(7) and 115(27) nmole·g-1.