Digestion methods for analysis of fly ash samples by atomic absorption spectrometry

The efficiency of different digestion methods (six microwave decomposition methods and a wet acid digestion method) in the solubilisation of six metal s (Cr, Ni, Cu, Pb, Cd, Zn), for their determination in fly ashes, was compa red. Five different mineral acid mixtures and two different microwave syste ms were tested. The study was carried out by analyzing two highly homogenis ed fly ash samples (from sewage sludge and city waste incineration) provide d by the Joint Research Centre of Ispra. Determinations were performed by a tomic absorption spectrometry and by inductively coupled plasma atomic emis sion spectrometry. The analytical performance of the laboratory was evaluat ed using the 1633a Coal Fly Ash Standard Reference Material of National Bur eau of Standards (NBS SRM 1633a), Results showed that a HNO3 microwave treatment was strong enough to solubil ise metals from the considered fly ashes. Moreover, microwave methods gener ally provided higher release than the classical aqua regia method, whereas no significant advantage was observed using a high performance microwave un it. (C) 1999 Elsevier Science B.V. All rights reserved.