ICP-AES Determination of 8 Elements in Ferrovanadium and Verification of Precision of the Method

An ICP-AES method for determination of 8 elements (i.e,. silicon, phosphorus, aluminum, nickel, chromium, copper and titanium) in ferrovanadium was proposed and precision of the method was verifed. The sample (0.500 0 g) was dissolved by heating with 20 mL of 50% (volume fraction) nitric acid solution first and then with 10 mL of 50% (volum fraction) hydrochloric acid solution during the course of which water was added intermittently into the solution to keep its volume around 25 mL. The solution was filtered into a 200 mL volumetric flask, and the filtrate was kept as mother solution for further use. The filter paper with its insolubles was transferred into a Pt-crucible and ashed in a muffle furnace at 250℃ for 20 min, and then fused with 0.3 g of a mixed flux containing anhydrous sodium carbonate and boric acid and boric acid (mixed in the mass ratio of 2:1) at 950℃ for 15 min. After cooling, the melt was taken up with 10 mL of hydrochloric acid solution with a volume ratio of 1:10. The solution obtained was combined with the mother solution in the 200 mL volumetric flask, and water was added to the mark. This solution was used as testing solution for ICP-AES analysis under the working condition of the instrument. C alibration curves (R>0.999) for the 8 elements were prepared with the standard solution and matrix matching method was used to overcome the matrix effect. Verification of precision of the method proposed was carried out according to the national standard of GB/T 6379.2-2004. Interlaboratory study was conducted among 10 laboratories by analyzing a set of 8 ferrovanadium samples with contents of the 8 elements in 6 gradient concentration levels. Values of repeatability standard deviation S_r and repeatability limit r, as well as the reproducibility standard deviations S_R and reproducibility limit R were calculated. And the functional relationships between r and w (mass fraction of the element), and between R and w for the 8 elements in various concentration ranges were finally determined, showing that satisfactory precision and accuracy were attained by the method, and that feasibility of the method was proved.