DETERMINATION OF LEAD IN A CHLORIDE MATRIX BY ATOMIC-ABSORPTION SPECTROMETRY USING ELECTROTHERMAL VAPORIZATION AND CAPACITIVELY COUPLED PLASMA ATOMIZATION

A simple and rapid method using graphite furnace vaporization and plas ma atomization for the determination of lead in a sodium chloride matr ix was developed, Samples were injected into the furnace of a commerci al graphite furnace atomic absorption/plasma emission spectrometer, A relatively low vaporization temperature of 750 degrees C was used to v aporize lead chloride preferentially from the bulk sodium chloride mat rix, The lead chloride molecules were then atomized by a capacitively coupled plasma. The lead atomic absorption signal is, therefore, separ ated from the sodium chloride background absorption temporally, Detect ion limits (3 sigma) in 3% m/v sodium chloride are 4 and 40 pg of lead using peak absorbance and integrated absorbance, respectively, for a 20 pi sample, The direct determination of lead in sea-water, however, suffers from matrix effects due to magnesium sulfate, Addition of oxal ic acid as a chemical modifier eliminates the magnesium sulfate interf erence, Detection limits (3 sigma) in a sea-water matrix are 28 and 2 pg of lead using peak absorbance and integrated absorbance, respective ly, The precision of the method is less than or equal to 7% RSD (five replicates of 20 mu l of a 25 ng ml(-1) Pb sample in either a sodium c hloride or sea-water matrix).