Determination of Trace Elements in High Purity Tungsten by Solid-Phase Extraction/ICP-MS

To establish a rapid trace-quantification scheme for elements contained in highly purified tungsten, we studied the most suitable conditions for separating the elements using solid-phase-extraction as a pretreatment for inductively coupled plasma-mass spectrometry (ICP-MS). We used chemically bonded silica gels belonging to the functional group of benzylsulfonic acid as extracting agent. Tungsten was anionized by adding hydrogen peroxide solution to a sample that had been decomposed with acid. We separated the cation trace impurities that were present in the chemically bonded silica gel of the ion-exchange type. The target elements retained in the chemicals were then eluted using 10 cm of 2 kmol/m nitric acid. Quantities of the obtained target elements were determined using ICP-MS. Highly sensitive quantification was established for 15 trace elements in highly purified tungsten, and for Be, Al, Mg, Mn, Fe, Co, Ni, Cu, Zn, Ga, Cd, In, Tl, Pb, and Bi with the following detection limits [3 ; ng/g (ppb)]: Be 0.11, Al 0.14, Mg 0.12, Mn 0.15, Fe 1.81, Co 0.086, Ni 0.082, Cu 0.092, Zn 0.12, Ga 0.074, Cd 0.012, In 0.069, Tl: 0.082, Pb 0.071, and Bi 0.036. [doi:10.2320/matertrans.MRA2008135]