Superiority of nitric acid for deproteinization in the determination of trace lithium in serum by graphite furnace atomic absorption spectrometry

Physiological level of trace lithium in human serum was determined by graphite furnace atomic absorption spectrometry (GFAAS). 3.5% HNO₃ (v/v) was employed as a protein precipitant for sample treatment and at the same time verified as a very effective chemical modifier to eliminate the interference of chloride. The analytical conditions for lithium determination in serum were investigated and the optimal pyrolysis and atomization temperatures were 800 °C and 2700 °C. The accuracy and precision of the method were tested by determining lithium in a RANDOX HN1530 assayed human multi-sera and a pooled human serum. The result was in good agreement with the target value and CV of the pooled human serum was 4.74% (n = 10). The characteristic mass, the limit of detection (LOD) of the proposed method were 0.8 pg and 0.01 μmol/L, respectively. Median ± S.E.M. of serum lithium in 220 Chinese people was 0.25 ± 0.02 μmol/L.