Abstract

An improved method has been developed to analyze the metallic contaminants in the non-volatile residue of liquid-phase tungsten hexafluoride (WF₆). This method uses a mixture of aqueous ammonia, aqueous hydrofluoric acid and aqueous nitric acid to dissolve the non-volatile residue, left behind when liquid-phase WF₆ is evaporated. The use of this aggressive mixture is much superior to the use of deionized water or aqueous ammonia, as has been the practice in the past. Using this aggressive matrix on the residue from a 220 g aliquot of WF₆, and analyzing the solution using a quadrupole-based ICP-MS instrument equipped with an inert sample introduction system, the following limits of detection are obtained: Na 0.5; K 1.3; Fe 0.8; Cr 0.7; Th 0.01; and U 0.01 ng  g⁻¹ WF₆.