Determination of trace elements in high purity molybdenum by glow discharge mass spectrometry.

Abstract

The commercially available molybdenum metals, including a rod (Jhonson Matthey batch No. 31825) of high purity, were analyzed for their trace impurities by using a VG9000 glow discharge mass (GD-MS) spectrometer equipped with a highly sensitive glow discharge cell, the so-called �Mega cell�, and a liq. N2 sample cooling system. The samples, mechanically shaped in rod form (2.3 mmX2.3 mmX22 mm or 2.0~2.3 mm in diameter and 20 mm in length), were washed with aqua regia and deionized water, and then dried just before use. Preliminary sputtering in the glow discharge cell was required for surface cleaning of the sample: 30 min for the determination of most elements and 2 h for C, O and Cl at ppb level. The discharge current was fixed to 3.0 mA and the discharge voltage was controlled at 1.00 + 0.05 kV for the determination. Most of the elements at ppm level could be determined with a RSD of 3% or less. However, the determination of titanium was quite difficult because the overlap of doubly charged Mo ions on all isotopes of singly charged Ti ion is unavoidable under the adopted resolution of 4000 or a little higher. For the typical 16 elements which could be determined by ICP-AES, furnace AAS etc., the analytical values obtained by GD-MS were in good or reasonable agreement with those by other methods except for C, O and ppb~ppt levels of U and Th. These results suggest that the VG recommended relative sensitivity factor used in this work is applicable to the analysis of high purity molybdenum metals. © 1992, The Japan Society for Analytical Chemistry. All rights reserved.