| High-purity magnesium and molybdenum & its alloys are the very important metal materials in aviation,energy resources,electronics,military and other fields.The accuracy of impurity content and purity analysis results not only directly affect the performance evaluation of anti oxidation and corrosion resistance of this kind of material,but also determine the accuracy and uncertainty range of the key characteristics of certified reference materials.At first,the method for determination impurity elements in high-purity magnesium were established by inductively coupled plasma-mass spectrometry(ICP-MS)in this paper.The semi-quantitative analysis results were obtained for 62 elements by ICP-MS.The content of 9 elements including Cr,Fe,Mn,Ni,Cu,Zn,Sn,Pb and Bi,which is not only higher than detection limit but also >1.0?g/g,were quantitatively analyzed by ICP-MS.Because of the serious mass spectrometry interferences,some trace elements such as Al,Si and Ca,were determined by the established ICP-AES analysis method.The standard addition is used as matrix matching.The sources of uncertainty were analyzed and evaluated for determination of impurity elements in high-purity magnesium by ICP-MS and ICP-AES,and the standard uncertainty of the analytical results of each element was calculated.For 65 trace impurities by ICP-MS method combined other elements with ICP-AES,the final purity and the uncertainty is 99.924%±0.002%.Based on the purity analysis method,the solid analysis method for pin-shaped high-purity magnesium by glow discharge mass spectrometry(GD-MS)is studied.Because of small superficial area,pin-shaped sample unstable discharge.It is 47.0 m A discharge current and 599 m L/min Argon gas flow that meet the experimental requirements.The pollution could be completely eliminated by setting the pre-sputtering time of 15 min.The isotopes and resolution were optimized.Three magnesium based standard samples were used to correct RSF.The proposed method was used for determination of 69 impurity elements in high-purity pin-shaped magnesium sample.The purity of high-purity magnesium determined by GD-MS method is 99.927%±0.014%.The results of the quantitative analysis of 12 trace impurity elements were analyzed by ICP-MS and ICP-AES,and the other elements were used GD-MS results,the final purity and the uncertainty were 99.926%±0.002%.On the basis of the above work,the purity analysis method of pin-shaped high-purity molybdenum was further studied by GD-MS.Due to the serious polyatomic ion interferences by molybdenum oxide and nitride,the trace cadmium in high-purity molybdenum is very hard to determine accurately even by high resolution spectrometry.ICP-Mass/Mass spectrometry together with the reaction cell technique has been studied to eliminate the interferences.111 Cd was chosen as analytical isotope.The gas flow rate was optimized as 0.4 m L/min for NH3 in the reaction cell.The established method by ICP-MS-MS was used for determination of trace cadmium in high-purity molybdenum sample.The final purity and uncertainty results by the three purity analysis methods for high-purity molybdenum were showed as the followeed: ICP-MS & ICP-AES method(66 elements: 99.971%±0.002%),GDMS(69 elements: 99.974%± 0.010%),multi method synthesis(69 elements: 99.976%±0.002%).Just as showed,GD-MS is accurate and reliable by comparing the other two methods in purity analysis.It can completely replace ICP-MS and other wet analysis methods for the accurate analysis of the high-purity magnesium metal at the level of3 N.In addition,the distinctive advantages,such as direct analysis,low detection limit,high resolution,small matrix interference,simple operation,time saving and so on,make GD-MS be an outstanding method for purity analysis.Especially for most of the trace impurity elements with the detection limit in two orders of magnitude lower than that of ICP-MS,GD-MS shall be much more predominant for the purity analysis of metal magnesium or molybdenum at 4N~6N or above high purity. |
PDF Full Text Request