Analysis of liquid-phase tungsten hexafluoride residue by inductively coupled plasma mass spectrometry with ultrasonic nebulization

Abstract

A method was refined for the determination of trace elemental contaminants in high-purity tungsten hexafluoride. The procedure is based on the collection of a liquid-phase sample of WF₆, generating a residue by evaporation of the sample and subsequent digestion in concentrated ammonia solution. After sample digestion and workup, analysis was performed by inductively coupled plasma mass spectrometry (ICP-MS) with ultrasonic nebulization. The reliability of the analysis method and instrument limits of detection were found to be superior to ICP-MS with a pneumatic nebulizer and water-cooled spray chamber. The following limits of detection (in ng cm^–3) were observed: Na, 0.2; Mg, 0.01; P, 3.2; K, 1.5; Cr, 0.02; Fe, 0.5; Ni, 0.03; Cu, 0.08; As, 0.07; Pb, 0.01; Th, 0.02; and U, 0.03.