Critical evaluation of novel dynamic flow-through methods for automatic sequential BCR extraction of trace metals in fly ash |
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Authors: | Warunya Boonjob María Rosende Manuel Miró and Víctor Cerdà |
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Institution: | (1) Department of Chemistry, Faculty of Sciences, University of the Balearic Islands, Carretera de Valldemossa Km. 7.5, 07122 Palma de Mallorca, Illes Balears, Spain |
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Abstract: | Two novel dynamic extraction approaches, the so-called sequential injection microcolumn extraction and sequential injection
stirred-flow chamber extraction, based on the implementation of a sample-containing container as an external extraction reactor
in a sequential injection network, are for the first time, optimized and critically appraised for fractionation assays. The
three steps of the original Community Bureau of Reference (BCR) sequential extraction scheme have been performed in both automated
dynamic fractionation systems to evaluate the extractability of Cr, Cu, Ni, Pb, and Zn in a standard reference material of
coal fly ash (NIST 1633b). In order to find the experimental conditions with the greatest influence on metal leachability
in dynamic BCR fractionation, a full-factorial design was applied, in which the solid sample weight (100–500 mg) and the extraction
flow rate (3.0–6.0 mL min−1) were selected as experimental factors. Identical cumulative extractabilities were found in both sequential injection (SI)-based
methods for most of assayed trace elements regardless of the extraction conditions selected, revealing that both dynamic fractionation
systems, as opposed to conventional steady-state BCR extraction, are not operationally defined within the selected range of
experimental conditions. Besides, the proposed automated SI assemblies offer a significant saving of operational time with
respect to classical BCR test, that is, 3.3 h versus 48 h, for complete fractionation with minimum analyst involvement.
Schematic illustration of automatic flow-based setups for dynamic fractionation of trace metals in fly ash
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Keywords: | Dynamic fractionation Sequential injection analysis Stirred-flow chamber extraction Microcolumn extraction Coal fly ash Trace elements |
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