A simple and practical wax-encapsulation method for air-sensitive XAS samples

Abstract

To facilitate X-ray absorption spectroscopy (XAS) measurements of air-sensitive samples, we present a simple method in which materials are encased in common paraffin wax to protect them from air and moisture. We demonstrate the efficacy of this approach using a highly reducing, air- and moisture-sensitive uranium(III) complex, the tris(amide) U[N(SiMe₃)₂]₃ (1). When finely dispersed in a boron nitride matrix and subsequently encased in inert paraffin wax, samples of 1 remain stable with no visible or spectroscopic degradation after several days under ambient conditions. The viability of this method for XAS measurements was further evaluated across a series of uranium compounds, ranging from uranyl species to highly air- and moisture-sensitive molecular complexes, at the uranium L₃-edge. Edge energy determinations were highly reproducible (±0.1 eV between replicates) and, where available, showed excellent agreement with literature values. This low-cost, effective, and versatile method offers a viable solution for XAS studies of air-sensitive compounds and materials.