Pre-concentration of trace metals from acidic sample solutions on a thin layer of activated carbon using dithizone as a chelating agent

Abstract

Acidic sample solutions were analysed by flame AAS and spectrophotometry, making use of the collection of trace amounts of Ag, Bi, Cu, Cd, Hg, Pb and Zn as their dithizonates on a thin layer of activated carbon. The metal chelates were then released from the activated carbon layer by digestion with 14 M HNO₃. The dependence of the trace element recoveries on the concentration of HNO₃ and HCI in the sample solution was investigated. Water samples, aluminium, salts and acids were analysed and the accuracy of the results was checked by electrothermal AAS or by pre-concentration with a thiuram disulphide precipitate. The detection limits were between 0.3 ng ml^–1(Cd) and 10 ng ml^–1(Hg) and the relative standard deviations varied from 1 to 8%. The recovery, separation factor and pre-concentration factor of the method are discussed.