Journal
JOURNAL OF CHROMATOGRAPHY A
Volume 1218, Issue 27, Pages 4199-4205Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.chroma.2011.01.076
Keywords
Flow field flow fractionation; ICP-MS; Isotopic exchange; Natural organic matter; Environmental availability
Funding
- Spanish Ministry of Science and Innovation [CTQ2009-14237-C02-01]
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The determination of the isotopically exchangeable fraction of metals in environmental solid samples (soils, composts, sediments, sludges, etc.) is used to know the amount of metal potentially available (E-value). Stable isotopes can be used for determination of E-values through the analysis of the aqueous phases from spiked suspensions. However, the presence of isotopically non-exchangeable metal forms in the aqueous phase led to overestimation of the E-values. In this paper, a method for monitoring the degree of isotopic exchange in function of the molecular mass and/or size of the metal form has been developed based on the direct coupling of asymmetrical flow field flow fractionation (AsFIFFF) with inductively coupled plasma mass spectrometry (ICP-MS) for on-line isotope ratio measurements. ICP-MS data acquisition parameters were stressed to avoid degradation of isotope ratio precision. Two sets of fractionation conditions were selected: a colloids separation, which allowed the separation of substances up to 1 mu m, and a macromolecules separation, designed to resolve small size substances up to 50 kDa. The methodology was applied to study the environmental availability of copper and lead in compost samples, where metals are mainly associated to different forms of organic matter. No significant differences on isotopic exchange were observed over the size range studied, validating the E-values determined by direct analysis of the aqueous phases. (C) 2011 Elsevier B.V. All rights reserved.
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