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Jia Y.-H.,National Analysis Center for Iron & Steel
Yejin Fenxi/Metallurgical Analysis | Year: 2016

Precision inspection of analytical instruments usually use 10 times standard deviation (S10). But in analytical standard, it just gives the repeatability limit (r) for 2 parallel analysis. S10 and r can not be directly compared. Two methods to evaluate the relationship between standard deviation (Sn) and repeatability limit (r) was proposed: χ2 distribution method gives S10≤0.49 r; range method gives S10≤0.52 r. The two methods get similar results, it maybe simplified as S10≤0.5 r. Through this way it can easily know whether the instruments satisfy the repeatability limit of analytical standard or not. Range method is suitable for the case of n≤10. © 2016, Central Iron and Steel Research Institute. All right reserved. Source


Han M.,National Analysis Center for Iron & Steel | Yang G.-W.,National Analysis Center for Iron & Steel | Qi R.,National Analysis Center for Iron & Steel | Hu J.-Y.,National Analysis Center for Iron & Steel
Yejin Fenxi/Metallurgical Analysis | Year: 2015

According to the insoluble characteristics of nickel-tungsten alloy, the sample was dissolved with nitric acid by heating at low temperature. The tungsten oxide coated on sample surface was chelated by adding hydrogen peroxide to fully dissolve the sample. Then, the determination method of trace cerium in nickel-tungsten alloy by inductively coupled plasma mass spectrometry (ICP-MS) was established. Under the selected instrumental conditions, the 140Ce was used as the isotope. The rhodium (20 μg/L) was selected as internal standard for the determination. The calibration curve was plotted using the signal strength ratio of cerium and rhodium as the vertical coordinate and using the mass concentration of cerium as the horizontal coordinate. The results showed that the linear relationship was good. The linear regression equation was y=0.688 x+0.047 with linear correlation coefficient of R2=0.999. The detection limit of cerium was 0.08 μg/g. The lower determination limit was 0.26 μg/g. The proposed method was applied to the determination of cerium in actual samples, and the relative standard deviations (RSD, n=9) of determination results were between 0.10% and 1.0%. The recoveries were between 88% and 117%. © 2015, Central Iron and Steel Research Institute. All right reserved. Source

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