HG-AAS Determination of Micro-amount of Lead in Citric Acid

The sample of citric acid was treated with con. H2SO4, and ashed by ignition at 550 ℃. The residue was taken up with HCl(5+95) and the species of Pb(Ⅱ) in the solution was oxidized to Pb(Ⅳ) by potassium ferricyanide, and then determined by hydride generation-atomic absorption spectrometry (HG-AAS) with KBH4 as reducing reagent and HCl (1+99) solution as carrying solution. Linear relationship between values of absorbance and mass concentration of lead was obtained in the range within 20 μg·L-1, with detection limit (3σ) of 2.6 μg·L-1. Three samples of citric acid were analyzed by the proposed method, values of recovery found by standard addition method were in the range of 90.5%-110.0%, with RSD′s (n=6) less than 5%.