Comparison of methods to evaluate heavy metals in organic wastes

Abstract

Abstract The conventional method for the digestion of residues using a mixture of nitric and perchloric acids was compared with the microwave procedure using both aqua regia and nitric acid as extractants, in order to determine which method fits better the routine measurements using inductively coupled plasma emission spectrometry (ICP‐AES). Urban domestic wastes, swine and dairy manure and NIES pond sediment certified reference material were used as samples. The microwave digestions were performed on sealed vessels by taking 500 mg of each residue and aqua regia (16 mL) or concentrated nitric acid (10 mL). The conventional nitric‐perchloric digestion was performed by heating 500 mg of each sample with 6 mL of HNO3 ‐HClO4 5+1 v/v in Pyrex digestion tubes until complete digestion. All extracts were analysed for Fe, Mn, Zn, Cu, Pb, Ni, Cr and Cd by ICP‐AES. Microwave extraction with aqua regia extracted higher amounts of metals from the certified pond sediment reference material than the USEPA‐SW 846‐method...