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

ENEA CRE Casaccia AMB/TEIN/CHIM, Via Anguillarese 301, 00060 Rome, Italy
Analytica Chimica Acta (Impact Factor: 4.51). 08/1999; 395(1-2):157-163. DOI: 10.1016/S0003-2670(99)00342-6


The efficiency of different digestion methods (six microwave decomposition methods and a wet acid digestion method) in the solubilisation of six metals (Cr, Ni, Cu, Pb, Cd, Zn), for their determination in fly ashes, was compared. Five different mineral acid mixtures and two different microwave systems were tested. The study was carried out by analyzing two highly homogenised fly ash samples (from sewage sludge and city waste incineration) provided by the Joint Research Centre of Ispra. Determinations were performed by atomic absorption spectrometry and by inductively coupled plasma atomic emission spectrometry. The analytical performance of the laboratory was evaluated using the 1633a Coal Fly Ash Standard Reference Material of National Bureau of Standards (NBS SRM 1633a).Results showed that a HNO3 microwave treatment was strong enough to solubilise metals from the considered fly ashes. Moreover, microwave methods generally provided higher release than the classical aqua regia method, whereas no significant advantage was observed using a high performance microwave unit.

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Available from: Zoltán Mester, Apr 28, 2014
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    • "A mixture of nitric acid and hydrogen peroxide is widely employed because they mineralise organic matter effectively and produce less spectral interference in ICP analyses [1]. Nitric acid has been reported to be strong enough to solubilize metals ISRN Analytical Chemistry from fly ashes [21], from soils with organic carbon content up to 38% [22], and from plant materials for environmental monitoring [23]. However, in general, plant samples require a more complete decomposition procedure due to the presence of high organic and/or silicon contents [24]. "
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    • "The best one for these materials seems to be the mineralization in an open system with sulfuric acid. Mester et al. [16] compared microwave decomposition methods and a wet acid digestion in the solubilization of Cr, Ni, Cu, Pb, Cd and Zn, for their determination in fly ash. The microwave methods included different combinations of concentrated mineral acids, such as: (1) HNO 3 , (2) HNO 3 , HF and H 3 BO 3 , (3) HNO 3 , HF, H 3 BO 3 with addition of H 2 O 2 , (4) HNO 3 , HF, HF and H 3 BO 3 (5) HNO 3 , HF, HClO 4 and H 3 BO 3 . "
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