Determination of traces of Ni in Li2CO3/Na2CO3 melts by graphite furnace atomic absorption spectrometry

A graphite furnace atomic absorption method is described for the determination of traces of Ni in 52 mole percent (mol.%) Li2CO3 and 48 mol.% Na2CO3 melts after dissolution of the sample in dilute nitric acid. Maximum pyrolysis and optimum atomisation temperatures for the analyte were determined in the presence of the Li and Na matrix constituents. Pre-pyrolysed ascorbic acid (typical amount of 5 μg) has been used as chemical modifier for effectively suppressing the chemical and spectral interferences of the Li/Na matrix, thus that the analysis can be conducted using acid-matched standard solutions. The results of the Ni analysis in synthetic sample solutions by calibration graph against acid-matched standards well agree with those obtained by the method of standard additions. Recoveries ranged from 99 to 101% and the relative standard deviation is around 3% at the 20 μg L−1 level. Moreover, the use of the chemical modifier leads to an improvement of the lifetime of the graphite tube. The Ni detection limit (3σ) in Li/Na carbonate melts for the proposed method is similar to that obtained in aqueous solution, i.e. 5 × 10−8 g analyte per gram of (Li0.52Na0.48) 2CO3 melt. This method is successfully applied to the determination of nickel in real carbonate melt samples.