Determination of traces of Ni, Co and Fe in Li_2CO_3/K_2CO_3 melts by flame atomic absorption spectrometry

摘要

A flame atomic absorption spectrometry (AAS) method is described for the determination of trace levels of Ni, Co, and Fe in 62 mole percent (mol.%) Li_2CO_3 and (mol.%) K_2CO_3 melts after dissolution of the sample in dilute nitric acid. A pneumatic nebulizer with a glass impact bead is used to sample introduction. The effect of the high salt loading of the solution on the analytical signals is minimized by optimization of acetylene flow-rate and height of observation above the burner head. Under the optimum conditions, the results of the analysis of synthetic sample solutions by aqueous standards calibration graphs well agree with those obtained by the method of standard additions. Recoveries ranged form 99 to 101% and the relative standard deviation is around 1%. Detection limits for Ni, Co and Fe in Li/K carbonate salts are similar to that in aqueous solutions, i.e. 0.5 * 10~(-6) g analyte/g (Li_(0.62), K_(0.38))_2CO_3. Furthermore, a background absorption is easily compensated by D_2 background correction, which does not affect the sensitivity. The proposed method is applied to the determination of cobalt in real melt samples.