Teflon-HPLC: A novel chromatographic system for application to isotope geochemistry and other industries

Abstract

Traditional column chromatography techniques are restricted by several factors, including limitations on column length, resin grain size, elution time, and a general inability to slowly ramp up or down reagent concentrations along a gradient. Likewise, most existing high-performance liquid chromatography (HPLC) systems are not amenable to certain column chromatography techniques that require highly concentrated acids.Here, we outline the development of a Teflon HPLC (T-HPLC) system for application to a wide variety of chromatography problems. The primary factors that set the T-HPLC system apart from any currently available chromatography procedure are the following: 1) a fluid flow path enclosed entirely by Teflon, 2) fully automated elution schemes controlled by computer software, which allows for fresh mixing of reagents for each elution step, and fine scale gradient/ramp elutions, 3) temperature control of the entire system (up to 80°C) for enhanced chemical separations and, 4) a modular design making the system easily adaptable to a variety of separation schemes.The effectiveness of the T-HPLC system is tested on two column techniques that are of particular interest to the geochemistry/cosmochemistry communities. The first application involves the separation of Ni from Mg, which is required for high precision Ni isotopic studies and for investigating the abundance of the extinct 60Fe radionuclide. The T-HPLC system greatly simplifies and improves upon the classical technique. In a single pass on an 80cm long column, we achieve excellent separation of Ni from Mg, with a much improved time frame (10h versus 70h). The second application is the separation of the individual rare earth elements from each other. The isotopic compositions of the multi-isotopic REEs (La, Ce, Nd, Sm, Eu, Gd, Dy, Er, Yb and Lu) may hold important information about nucleosynthetic processes, cosmic-ray exposure effects in meteorites and airless bodies, and mass fractionation effects. For this application, we also developed a computer simulation that uses experimentally determined partition coefficients to simulate an elution curve in order to optimize the actual column elution scheme. Overall, we were able to achieve excellent separation of the multi-isotopic REEs from each other.Although the two applications that we explore are in the fields of geochemistry/cosmochemistry, the modular design and adaptability make the T-HPLC system useful to a wide array of scientific fields and industries.