Study On Trace Elemental Analysis Of High-purity Molybdenum And Titanium

The determination of trace impurities in high purity molybdenum powder,ammonium molybdate and molybdenum oxide by internal standard correction-ICP-MS was described. The analysis of high purity titanium and molybdenum was studied by Glow discharge mass spectrometry.The determination of results were compared with ICP-MS results, in order to determine the accuracy of the experimental results.Finally uncertainty of experimental results was evaluated.Various determination of impurities in high-purity metal analysis methods and analysis methods in high-purity metals by ICP-MS, GD-MS at home and abroad in recent decades was introduced in literature review. By comparison of various methods, the analysis of trace impurities by ICP-MS and GD-MS have very obvious advantages.In this paper, the critical parameters of ICP-MS including RF Power, carrier gas, sample depth and RF matching were optimized as follows:RF Power1450W, RF matching1.8V, carrier gas0.85L/min,and sample depth8.5mm.Under the above condition, The experiment of internal standard element was carried out, and4Sc was selected as the internal standard element of Mg, Al, Fe, V, Cr, Mn, Co, Ni, Cu and Zn,133Cs was selected as the internal standard element of Sn、Sb,185Re was selected as the internal standard element of Ta, W, Pb, Bi.Then using internal standard calibration-ICP-MS was successfully detected the impurities in high purity molybdenum powder and ammonium molybdate, molybdenum oxide content. The detection limit of impurities in high purity molybdenum powder was in the range of0.057～0.35ng/mL, the low limit of determinations were in the range of0.29～1.8ng/mL, RSD of impurities determinated value was in the range of1.6%～12%, the recoveries of the impurities were in the range of94%～109%. By calculating the total content of impurities in high-purity molybdenum powder as17.4μg/g.The detection limit of impurities in ammonium molybdate was in the range of0.060～0.38ng/mL, the low limit of determinations were in the range of0.3-1.9ng/mL, RSD of impurities determinated value was in the range of1.6%～10.7%, the recoveries of the impurities were in the range of94%～110%. By calculating the total content of impurities in ammonium molybdate as17.5μg/g.The detection limit of impurities in molybdenum oxide was in the range of0.057～0.35ng/mL, the low limit of determinations were in the ange of0.29～1.8ng/mL, RSD of impurities determinated value was in the range of209%～11.3%, the recoveries of the impurities were in the range of92%～107%. By calculating he total content of impurities in molybdenum oxide as16.8μg/g.By evaluating the uncertainty of impurity elements in high purity molybdenum (?)owder, the expanded uncertainty of the total content of impurities in high purity (?)olybdenum powder is9.7μg/g, and the purity of high-purity molybdenum powder is (99.9982～0.0010)%. The expanded uncertainty of the total content of impurities in ammonium molybdate is11μg/g, and the purity of ammonium molybdate is (99.9982±3.0011)%. The expanded uncertainty of the total content of impurities in molybdenum (?)xide is12μg/g, and the purity of molybdenum oxide is (99.9983±0.0012)%.By analysis of the sources of uncertainty, the uncertainty comes mainly from the repeatability of experiments and the mass concentration of the the measured elements of sample.In this paper, the critical parameters of GD-MS including Current, voltage, resolution and sensitivity were optimized.64trace impurities including Mg, Al, Ti, V, Cr, Mn, Fe, Co,Cu, Zn, Ni, As, Sn, Sb, W, Ta, Pb, Bi was successfully detected in high purity titanium, and66trace impurities was successfully detected in high purity molybdenum. The detection limit was0.01μg/g, RSD of impurities determinated value was in the range of5.9%～55%.The separation of Mg, Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Ni, As, Sn, Sb, W, Ta, Pb, Bi from high purity itanium was on-line determinated by Ion-Chromatography-ICP-MS.The conditions for the adsorption of impurity ions on ion exchange colume include effects of acidity and flow rate of sample solution, composition and flow rate of elution.The optimum conditions were column acidity0.15mol/L,flow rate of sample solution1.0mL/min, elution acidity of HNO33mol/L and elution rate1.0mL/min. The accuracy of test results were verified by the spiked recovery experiments. RSD of impurities determinated value was in the range of3.0%～11%.Finally, the experimental results that determined by ICP-MS and GD-MS were compared, and analysis of the results by GD-MS is considerable accuracy with no standard samples. Compare the results of GD-MS and ion chromatography-ICP-MS, n order of magnitude of μg/g, relative deviation of most elements in titanium were less than17%. Compare the results of GD-MS and ICP-MS, in order of magnitude of μg/g, relative deviation of most elements in molybdenum were less than18%. By F test and t test,the results showed that these two methods have good consistency in the level of μ-g/g, the consistency become worse with the reduction of the element content.The experimental results were determined by ICP-MS were treated as accurate values and the relative sensitivity factor(RSF) of Mg, Cr, Mn, Fe, Ni, Cu, Zn in conditions of titanium and Mg, Cr, Fe, Ni, Zn, W in conditions of molybdenum matrix are rectified.Calculation of sample purity as follows:In the case of the determination of64elements, the total content of impurity elements in highly pure titanium is18μg/g, and the purity of highly pure titanium is99.9982%. In the case of the determination of66elements, the total content of impurity elements in high purity molybdenum is13μg/g, and the purity of highly pure molybdenum is99.9987%.