Limits of the Linear Accumulation Regime of DGT Sensors

Mongin, Sandrine; Uribe, Ramiro Restrepo; Rey-Castro, Carlos; Cecília, Joan; Galceran, Josep; Puy, Jaume

doi:10.1021/es400609y

Cited by 21 publications

(22 citation statements)

References 36 publications

(95 reference statements)

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“…Let us now concentrate on the limit of short times where Mg bound to the resin is expected to be far from the equilibrium concentration, but long enough to neglect transient effects [27][28][29] . As seen in Fig.…”

Section: Experimental Accumulations and Percentages Of Metal Accumulamentioning

confidence: 99%

Accumulation of Mg to Diffusive Gradients in Thin Films (DGT) Devices: Kinetic and Thermodynamic Effects of the Ionic Strength

et al. 2016

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Availability of magnesium is a matter of concern due to its role in many environmental and biological processes. Diffusive Gradients in Thin Films (DGT) devices can measure Mg availability in situ. This work shows that Mg accumulation in water largely increases when ionic strength (I) decreases. This phenomenon can be explained from (i) the increase of both the association equilibrium (K) and rate (k) constants for the reaction between Mg cations and resin sites, and (ii) the growing contribution of the partitioning of Mg cations at the resin-gel interface, as I decreases. Two theoretical models that take into account electrical interactions among Mg cations, background electrolyte, and resin sites can successfully be used to determine k and K at each I. Both models yield similar k values, which fulfill an expression for the kinetic salt effect. For freshwater (with a typical salinity of 10 mM and circumneutral pH), the binding of Mg is so fast and strong that the simplest perfect-sink DGT expression can be helpful to predict (overestimation lower than 5%) the accumulation in solutions with Mg concentrations up to 1 mM whenever the deployment time is below 9 h. Perfect sink conditions can still be applied for longer times, in systems with either a lower I or a lower Mg concentration.

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Section: Experimental Accumulations and Percentages Of Metal Accumulamentioning

confidence: 99%

Accumulation of Mg to Diffusive Gradients in Thin Films (DGT) Devices: Kinetic and Thermodynamic Effects of the Ionic Strength

et al. 2016

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“…where A is the effective area of the gel-solution interface. A detailed plot of the accumulated nM in front of increasing deployment times would reveal 4 regimes: transient (when the flux is growing), (quasi) steady-state regime (practically constant flux), approach to equilibrium (decreasing flux) and equilibrium (null flux) [26,27] . The practical use of DGT has consisted in focusing in the steady-state regime (while neglecting the very small effects of the short transient regime), so that, the time integral of the flux becomes just M n JAt = (2) Thus, from the processing of the accumulations, DGT is also providing a quantification of the flux.…”

Section: Key Concepts: Accumulation Fluxes and Lability Degreementioning

confidence: 99%

Interpretation of diffusion gradients in thin films (DGT) measurements: a systematic approach

Galceran

Puy

2015

Environ. Chem.

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Environmental context Dynamic speciation of an element in a natural medium is essential for understanding its availability. The technique of diffusion gradients in thin films (DGT) has become a widely used tool for in situ environmental studies, being applied to determine fluxes of metal cations, anions, organics and nanoparticles. The interpretation of the measurements with suitable physicochemical models gives valuable insights into the behaviour of the system. Abstract Gaining insight into the physicochemical processes integrated in a DGT (diffusion gradients in thin films) measurement and combining them in a model can assist in retrieving fundamental information, both qualitative and quantitative, on the probed system. New experiments (such as varying the thicknesses of the gel or the resin layer) and their mathematical treatment to extract meaningful parameters have been suggested from theoretical considerations. The concept of lability degree is useful in describing an interpretation of the DGT concentration as the summation of the free metal concentration plus the labile fraction of all complexes multiplied by a ratio of diffusion coefficients. In some cases, the lability degree can be directly estimated with specific measurements and a very simple expression. We review the current status of these interpretations, including numerical simulations, with special focus on analytical expressions, because they can be more accessible to the standard DGT practitioner. Present limitations and challenges for future work in DGT interpretation are also discussed.

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“…1, is that the surface of the resin layer acts as a perfect planar sink (Mongin et al 2013). This implies that the binding to the resin should be strong, irreversible, and almost instantaneous.…”

Section: Uptake Rate Experiments For Pim-dgtmentioning

confidence: 99%

Exploring new DGT samplers containing a polymer inclusion membrane for mercury monitoring

Turull

Elías

Fontàs

et al. 2016

Environ Sci Pollut Res

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A polymer inclusion membrane (PIM) made of cellulose triacetate as a polymer and the task specific ionic liquid (IL) trioctylmethylammonium thiosalicylate (TOMATS) was assembled as a new Diffusive Gradients in Thin film (DGT) device to test its efficiency as a binding phase for mercury (Hg) monitoring. The effect of IL content was assessed, showing that higher TOMATS percentage is better for short deployment studies (up to hours), whereas for long-term exposure (up to days), a lower content can be more suitable. Different configurations of PIM-DGT samplers have been tested under controlled conditions and compared with in-house DGT conventional ones, manufactured with thiol groups as resin layer, for the determination of labile Hg. According to our results, a nonlinear accumulation profile of Hg with deployment time for the different designs of PIM-DGT was observed, limiting the range of applicability of the DGT technique. Promising results for the efficient removal of Hg from aqueous solutions and/or environmental monitoring studies were obtained with TOMATS.

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Limits of the Linear Accumulation Regime of DGT Sensors

Cited by 21 publications

References 36 publications

Accumulation of Mg to Diffusive Gradients in Thin Films (DGT) Devices: Kinetic and Thermodynamic Effects of the Ionic Strength

Accumulation of Mg to Diffusive Gradients in Thin Films (DGT) Devices: Kinetic and Thermodynamic Effects of the Ionic Strength

Interpretation of diffusion gradients in thin films (DGT) measurements: a systematic approach

Exploring new DGT samplers containing a polymer inclusion membrane for mercury monitoring

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