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Performance of DGT (diffusive gradients in thin films) for measuring Ca and Mg in freshwater.

Dahlqvist, Ralf and Zhang, Hao and Ingri, Johan and Davison, William (2002) Performance of DGT (diffusive gradients in thin films) for measuring Ca and Mg in freshwater. Analytica Chimica Acta, 460 (2). pp. 247-256. ISSN 0003-2670

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Abstract

Measurements of the major cations Ca and Mg by the technique of diffusive gradients in thin films (DGTs) were systematically evaluated. The concentration in solution was calculated using Fick’s first law of diffusion from the directly measured flux to the DGT device. A selective cation exchange resin (Bio-Rad Chelex®100), which has been used extensively with DGT for trace metals, such as Cd2+, Cu2+ and Ni2+, was used for this work. Elution of Ca and Mg from the resin with 1 M HNO3 was very reproducible. Measurements of Ca and Mg concentrations in synthetic solutions agreed well with the theoretical predictions. The negative response on uptake caused by lowered pH was investigated. Uptake was found to decline below pH 5. The capacity of the DGT device for Ca and Mg was also investigated to establish maximum deployment times for given concentrations. Experiments with filtered and modified lake water show that DGT can be used to measure Ca and Mg when trace metals are present in the solution. An in situ deployment of DGT combined with an ultrafiltration study suggest that the Mg concentration measured by DGT is similar to the concentration found in the fraction <1 kDa.

Item Type: Article
Journal or Publication Title: Analytica Chimica Acta
Uncontrolled Keywords: Calcium ; Magnesium ; Diffusion ; Diffusive gradients in thin films ; Ion exchange ; pH
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 21457
Deposited By: ep_ss_importer
Deposited On: 14 Jan 2009 14:39
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 15:47
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21457

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