DETERMINATION OF TRACE METALS AT LOW LEVELS BY FLAME ATOMIC ABSORPTION SPECTROMETRY (FAAS) USING VARIOUS ACID DIGESTION MIXTURES

摘要

A flame AAS method for determination of Cu, Pb, Zn, Ni, Co, Ag, Cd, Li, Rb and Cs in soil and stream sediment samples have been described. The method involves sample decomposition by various acid mixtures e.g. HNO_3, aqua regia or HNO_3 - HF - HClO_4 followed by measurement of the trace metals by F-AAS techniques. A comparative study has been carried out for extraction of the elements with acid digestion mixture, and it is observed that about 95 percent extraction is achieved for Cu, Pb, Zn, Ni, Co, Ag and Cd by HNO_3 digestion, 97-98 percent extraction by aqua-regia digestion and complete extraction by HNO_3 - HF - HClO_4 digestion. Thus, the HNO_3 - HF - HClO_4 digestion procedure is recommended in soil and stream sediment samples for determination of Cu, Pb, Zn, Ni, Co, Cd, Ag, Li, Rb & Cs by FAAS technique.The detection limit achieved for Cu, Pb, Zn, Ni, Co, Li and Rb is 1 ppm, for Cd and Ag is 0.5 ppm and, for Cs is 2 ppm. Several international standard samples have been analysed following the procedures and the results are presented.