Donnan Membrane Technique (DMT) for Anion Measurement
| Autor: | Flora Alonso Vega, Willem H. van Riemsdijk, Erwin J. M. Temminghoff, Liping Weng |
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| Jazyk: | angličtina |
| Rok vydání: | 2010 |
| Předmět: |
Anions
Models Molecular dissolved organic-matter Bodemscheikunde en Chemische Bodemkwaliteit Diffusion Kinetics colloidal particles Analytical chemistry activity model metal-ion concentrations Analytical Chemistry Ion Humic acid heavy-metals sandy soil chemistry.chemical_classification Aqueous solution WIMEK Chemistry Osmolar Concentration aqueous-solutions chemical speciation Charged particle water extracts Membrane Models Chemical Ionic strength soil solution Algorithms Soil Chemistry and Chemical Soil Quality |
| Zdroj: | Analytical Chemistry 82 (2010) 7 Analytical Chemistry, 82(7), 2932-2939 |
| ISSN: | 0003-2700 |
| DOI: | 10.1021/ac9029339 |
| Popis: | Donnan membrane technique (DMT) is developed and tested for determination of free anion concentrations. Time needed to reach the Donnan membrane equilibrium depends on type of ions and the background. The Donnan membrane equilibrium is reached in 1 day for Cl(-), 1-2 days for NO(3)(-), 1-4 days for SO(4)(2-) and SeO(4)(2-), and 1-14 days for H(2)PO(4)(-) in a background of 2-200 mM KCl or K(2)SO(4). The strongest effect of ionic strength on equilibrium time is found for H(2)PO(4)(-), followed by SO(4)(2-) and SeO(4)(2-), and then by Cl(-) and NO(3)(-). The negatively charged organic particles of fulvic and humic acids do not pass the membrane. Two approaches for the measurement of different anion species of the same element, such as SeO(4)(2-) and HSeO(3)(-), using DMT are proposed and tested. These two approaches are based on transport kinetics or response to ionic strength difference. A transport model that was developed previously for cation DMT is applied in this work to analyze the rate-limiting step in the anion DMT. In the absence of mobile/labile complexes, transport tends to be controlled by diffusion in solution at a low ionic strength, whereas at a higher ionic strength, diffusion in the membrane starts to control the transport. |
| Databáze: | OpenAIRE |
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