Strategies in the application of the Donnan membrane technique.

L.P. Weng, F.A. Vega, W.H. van Riemsdijk

Research output: Contribution to journalArticleAcademicpeer-review

14 Citations (Scopus)

Abstract

e Donnan membrane technique (DMT) can be applied to measure free ion concentrations both in laboratory and in situ in the field. In designing DMT experiments, different strategies can be taken, depending on whether accumulation is needed. (1) When the free ion concentration is above the detection limit of the analytical technique (e.g. ICP-MS), no accumulation is needed and no ligand is added to the acceptor. Measurement can be based on the Donnan membrane equilibrium. (2) When an accumulation of less than 500 times is needed, an appropriate amount of ligand can be added to the acceptor and measurement can be based on the Donnan membrane equilibrium. (3) When an accumulation factor of larger than 500 times is needed, a relatively large amount of ligand is added to the acceptor and measurement can be based on the transport kinetics. In this paper, several issues in designing the DMT experiments are discussed: choice of DMT cell, measurement strategies and ligands and possible implication of slow dissociation of metal complexes in the sample solution (lability issue). The objective of this paper is to give better guidance in the application of DMT for measuring free ion concentrations in both synthetic and natural samples.
Original languageEnglish
Pages (from-to)466-474
JournalEnvironmental Chemistry
Volume8
Issue number5
DOIs
Publication statusPublished - 2011

Keywords

  • metal-ion concentrations
  • soil solution
  • chemical speciation
  • organic-matter
  • heavy-metals
  • sandy soil
  • dynamic speciation
  • humic substances
  • model parameters
  • trace-metals

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