Determination of lead in a chloride matrix by atomic absorption spectrometry using electrothermal vaporization and capacitively coupled plasma atomization

Abstract

A simple and rapid method using graphite furnace vaporization and plasma atomization for the determination of lead in a sodium chloride matrix was developed. Samples were injected into the furnace of a commercial graphite furnace atomic absorption/plasma emission spectrometer. A relatively low vaporization temperature of 750°C was used to vaporize lead chloride preferentially from the bulk sodium chloride matrix. The lead chloride molecules were then atomized by a capacitively coupled plasma. The lead atomic absorption signal is, therefore, separated from the sodium chloride background absorption temporally. Detection limits (3σ) in 3% m/v sodium chloride are 4 and 40 pg of lead using peak absorbance and integrated absorbance, respectively, for a 20 μl sample. The direct determination of lead in sea-water, however, suffers from matrix effects due to magnesium sulfate. Addition of oxalic acid as a chemical modifier eliminates the magnesium sulfate interference. Detection limits (3σ) in a sea-water matrix are 28 and 2 pg of lead using peak absorbance and integrated absorbance, respectively. The precision of the method is ≤7% RSD (five replicates of 20 μl of a 25 ng ml-1 Pb sample in either a sodium chloride or sea-water matrix).