Loading...
Investigating methods for the speed-up of intra-lanthanide chromatographic systems
Parler, Adam W.
Parler, Adam W.
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2025
Date Submitted
Keywords
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
2026-05-11
Abstract
High-purity separations of elements from nuclear forensic samples that are also fast have long been a challenge. The simplest analytical-scale separations for most research are based on relatively slow gravity-fed column chromatography, which trades speed for purity. However, in nuclear forensic applications, speedy separation methods are essential to backtracking and identifying the origin of nuclear materials quickly. One essential separation for nuclear forensics applications is the separation of individual lanthanide elements. While many sets of mixed elemental samples are difficult to separate, few are more difficult than intra-lanthanide separations. The lanthanide elements have very similar chemistries, which make their separations extremely tedious. These separations can take hours to complete and take focus away from other necessary tasks in fission product analysis. One way to increase the efficiency of intra-lanthanide separations would be to automate the gravity-fed chromatographic system, but progress in this area has been slow. The focus of this project centers around development of various methods to not only automate the lanthanide separation system but to also speed up the gravity column chromatography. A variety of approaches are taken to ensure the reduction in human interaction time with the lanthanide separation. Through each method, it will be shown how improvements can be made to lanthanide fractionation and how time can be saved on their laborious separation.
The development of a chromatography elution gradient generally requires many experiments due to the large number of variables that contribute to column performance. The development time for new gradients can be months to years. The first portion of this project aims to drive down development time for new gradients. This can be accomplished by narrowing the number of gradients that must be tested experimentally and identifying inefficiencies in existing gradients that might extend separation times unnecessarily. The major innovation to come from this effort is an eluant profile analyzer that can quantify how well a chromatography separation is affected. By tying a simple chromatography model and the profile analyzer together and sending the output to a minimization method, the elution gradient can be optimized to provide the best separation for a set of analytes under a set of user supplied constraints. This software package, termed LanPy, was validated by optimizing separations of a set of light and a pair of heavy lanthanides. The acid gradient provided by the software was found to be optimized for this set of analytes and provided accurate results for what the chromatogram would look like. This software is intended to be widely applicable to many different chromatography systems, not just the lanthanides.
This project also investigated how the lanthanides extracted on LN resin respond to changes in temperature to understand if a temperature gradient along the extraction chromatography column. Several phenomena that affect chromatography performance have a temperature dependence. If the location that analytes elute from the column could be shifted by the presence of a temperature gradient, one might be able to exploit this to decrease the amount of time lanthanide chromatography takes to complete. Previous studies have shown that lanthanide-HDEHP separations show a temperature dependence, although this was determined by liquid-liquid extraction experiments. To explore how temperature would affect lanthanides in chromatography, columns were run at differing temperatures and their chromatograms compared, looking for shifts in each peak's elution position. When no change was found, a series of batch resin studies was conducted at several temperatures. This study showed no differences in the lanthanide K$_D$ values at varying temperatures. A final study using undiluted HDEHP in a liquid-liquid extraction system explored how well europium would be extracted at different temperatures. When results showed no change in the partitioning at different temperatures, it was concluded that the concentration of HDEHP affects the temperature response of lanthanide-HDEHP separations and changes in temperature could not be used to improve lanthanide separation performance with LN resin.
The final part of this project worked to develop an automation system that could take over the monotonous tasks associated with lanthanide chromatography elution. Once the lanthanides are loaded onto the column, each fraction's acid preparation, elution monitoring, and collection become very repetitive. Because of the chemical similarities among the lanthanides and the necessity in collecting well partitioned fractions, the separation regularly takes more than 12 hours. Much of that time, however, is spent watching the columns elute, time that could be much better spent on important work. An automated system was designed to remove the burden of running the chromatography columns from researchers and perform these tasks itself. The system can position the columns above the appropriate collection vessels, mix its own acid to specific concentrations, deliver the acid to the columns, and monitor the column output for elution completion. Once the user provides an elution gradient, the system will run the elution autonomously. When the system was ultimately tested, it was discovered that it was not able to replicate a human produced chromatogram and is ultimately not able to replace human operators at this time.
Associated Publications
Rights
Copyright of the original work is retained by the author.