2002 Volume 42 Issue Suppl Pages S122-S127
When a small amount of metallic sample such as steel was heated in a graphite furnace used on electrothermal-atomic absorption spectrometry (ET-AAS), trace Pb, Ag, Cu and Mn in the sample were evaporated out of it, atomized and determined by AAS. A small sample was used for one determination. Mass of the sample was from about 20 to 600 μg. A graphite furnace was continuously used to atomize an analytical sample one by one. Appearance time and shape of an atomic absorption signal were affected by heating temperature of the graphite furnace (so-called atomization temperature). The appearance time of the signal shifted early with an increase in atomization temperature. Peak area of the signal was proportional to concentration of trace element in a sample, but height was not. Therefore, peak area of the signal was measured for determination of the trace elements. Detection limits of Pb, Ag, Cu and Mn in steel were 0.034 μg g-1 (for 500 μg of sample), 0.01 μg g-1 (600 μg), 0.3 μg g-1 (300 μg) and 0.8 μg g-1 (50 μg), respectively. By the way, an absorption signal of Pb consisted of two peaks that first one is small and another is large. The origin that two peaks were generated was examined by interruption of atomization for a solid sample and by heat-treatment of a solid sample before atomization. It became clear that the first peak was made from Pb in grain boundary of polycrystalline steel and another peak was made from Pb as particle in grain of the steel. Similarly trace Ag, Bi and Zn in polycrystalline steel showed double peak signals. As evaporation rate of trace Cu and Mn in a grain of steel was very slow, heating for atomization was repeated several times while absorption signal of Cu or Mn was detected .
