Direct determination of copper and lead in sewage sludge by solid sampling-graphite furnace atomic absorption spectrometry — study of the interference reduction in the gaseous phase working in non-stop flow conditions

Graphite furnace atomic absorption spectrometry is most useful for the determination of metals in solid samples when samples with a slow or complicated dissolution process are used. Its application to inorganic matrixes (especially geological material), therefore, appears to be a field of great interest. However, most of the papers published to date deal with organic samples. In the present paper two different strategies for the direct determination of metals in inorganic samples are proposed depending on the relationship between the analyte atomization temperature and the vaporization temperature of the matrix. For the more complicated case where both temperatures are similar, working in non-stop flow conditions is proposed because it permits a considerable reduction of interferences in the gas phase. This way the determination of lead and copper in a sewage sludge sample was carried out. The results can be considered as satisfactory with regard to both accuracy and precision (R.S.D. of 7.8% and 5.7%, for Pb and Cu, respectively), as they are similar to previous ones obtained for mainly organic less problematic samples.