Methods are provided for characterizing samples containing chemical elements such as rare earth elements, actinides, and heavy transition metals by treating the samples to form volatile complexes of the elements (e.g., β-diketonate complexes or other organic ligand complexes of the elements) and then analyzing the complexes, for example, via gas-phase thermochromatography. Also provided are methods for separating and/or recovering such chemical elements. The methods produce less waste and can be performed more rapidly than conventional liquid extraction methods and can provide separated elements of high purity (e.g., 99.9999% purity).