(250a) Predicting Chromatographic Separations of Lanthanide Chelates for Nuclear Forensics

In an effort to meet the growing demand for more rapid separation methods, this work reports the development and thermodynamic characterizations of organometallic species as a vehicle for the rapid separation of volatile nuclear fission products. Volatile organometallic complexes can be rapidly separated from each other via gas phase chromatographic separations due to differences in adsorption enthalpy. Because adsorption and sublimation thermodynamics are linearly correlated, there is considerable motivation to determine sublimation enthalpies to improve the ability to predict separations effectiveness. A method of using thermogravimetric analysis (TGA) is employed in this study on thirteen lanthanide 1,1,1,5,5,5-hexafluoroacetylacetone (hfac) complexes (Ln[hfac]₄). Sublimation enthalpies are determined using the Langmuir method involving isothermal jump heating. An empirical correlation is used to estimate adsorption enthalpies of lanthanide complexes on a quartz column from the sublimation data. TGA-MS and melting point analysis are used to confirm sublimation as well as confirm the stability of the chelate through the sublimation region. Finally, a Monte Carlo model based on single-atom chemistry used for simulating separations on a thermochromatographic column is briefly described.