Analytical related problems in metal and trace elements determination in industrial waste landfill leachates

The periodic analytical control of waste landfill leachate is of fundamental importance not only to check the presence of possible toxic substances, but also to assess changes in concentration levels and behaviour with time. This work identifies some of the difficulties which arise during the analysis of some heavy metals and trace elements in leachate samples from a controlled industrial wastes landfill located in north Italy. The analytical problems encountered using both electro-thermal atomic absorption spectroscopy (ETAAS) and neutron activation analysis (NAA) for the determination of a series of elements, Cu, Cd, Pb, Ni, Mn, V, As, Se, Sb, Th, Sn, Cs, W, Cr, with concentration often at nanogram levels, are presented and evaluated. To solve these problems two selective chemical procedures have been developed to separate and to eliminate the matrix interfering compounds or elements (i.e., organic matter, complexing agents, Cl − , Br − , S 2− , Na + ) which reduce and in some cases impair the sensitivity of the technique. For the analyses by ETAAS a preliminary preconcentration and separation procedure, based on the ion exchange resin Chelex-100 has been developed to determine Pb, Cd, Co, Cu, Ni and Sn. In the case of NAA a specific radiochemical separation had to be studied for the analysis of Sn, V, W, Mn, Cr, As, Sb, Se, Th in presence of high bromine and sodium concentrations. Procedures blanks and yields have been controlled and evaluated and quality assurance measurements have been carried out analyzing, with the proposed methods, standard reference materials from BCR and NIST. Furthermore, different mineralization procedures using both microwave and Teflon bomb have been compared and evaluated.