DIRECT DETERMINATION OF ULTRATRACE COPPER AND IRON IN LEAD AND ZINC METAL BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY USING THE GRAPHITE CUP DIRECT INSERTION TECHNIQUE

The graphite cup direct insertion technique in inductively coupled plasma atomic emission spectrometry was applled to the direct determination of trace amounts of copper and iron in lead and zinc metal. A piece of lead or zinc metal, 2-20 mg, was directly inserted into the plasma with a graphite cup insertion device to determine copper and iron at the ng/g or mu-g/g level. Copper and iron, which have higher boiling points than those of lead and zinc, began to evaporate after almost complete matrix evaporation. This phenomenon allows the elimination of chemical and spectroscopic interference due to matrix elements. Since the time-dependent emission profiles of copper and iron in metal samples were different from those in standard solutions, quantitative analyses were performed by the peak integration method using standard solutions, where relative standard deviations were 5-20% for metal samples. The values for iron and copper obtained by the direct sample analysis were in good agreement with the certified values of reference materials.