Diffusive gradients in thin films

Van Moorleghem C, Six L, Degryse F, Smolders E, Merckx R. Effect of organic P forms and P present in inorganic colloids on the determination of dissolved P in environmental samples by the diffusive gradient in thin films technique, ion chromatography, and colorimetry. Anal. Chem. 2011 83 5317-5323. 

Zhang, H. and Davison, W. (1995) Performance characteristics of diffusion gradients in thin films for the in situ measurement of trace metals in aqueous solution. Anal. Client., 67, 3391-3400. 

Zhang, H. and W. Davison. 2000. Direct in situ measurements of labile inorganic and organically bound metal species in synthetic solutions and natural waters using diffusive gradients in thin films. Anal. Chem. 72 4447 1457. 

Garmo, O.A., O., Royset, E., Steinnes, and T.P. Flaten. 2003. Performance study of diffusive gradients in thin films for 55 elements. Anal. Chem. 75 3573-3580. 

Li, W., H. Zhao, P.R. Teasdale, R. John, and F. Wang. 2005. Metal speciation measurement by diffusive gradients in thin films technique with different binding phases. Anal. Chim. Acta 533 193-202. 

Meylan, S., N. Odzak, R. Behra, and L. Sigg. 2004. Speciation of copper and zinc in natural freshwater Comparison of voltammetric measurements, diffusive gradients in thin films (DGT) and chemical equilibrium models. Anal. Chim. Acta 510 91-100. 

Speciation is best carried out directly in the aquatic system, without sampling. This has been possible since the development of Diffusive Equilibrium in Thin Films (DET) and Diffusive Gradient in Thin Films (DGT) probes.31 The DET probe consists of a very thin gel layer that is immersed in the aquatic system and allowed to equilibrate with the bulk solution. The concentration of solutes in the gel is similar to that in the bulk solution for all solutes that can diffuse through the pore openings of the gel (some gels have open pores >5 nm and some gels have restricted pores <1 nm). The DGT... 

Leermakers, M., Y. Gao, C. Gabeille, et al. 2005a. Determination of high resolution pore water profiles of trace metals in sediments of the Rupel River (Belgium) using DET (diffusive equilibrium in thin films) and DGT (diffusive gradients in thin films) techniques. Water Air Soil Pollut. 166 265-286. 

Wamken, K.W., H. Zhang, and W. Davison. 2004. Analysis of polyacrylamide gels for trace metals using diffusive gradients in thin films and laser ablation inductively coupled plasma mass spectrometry. Anal. Chem. 76 6077-6084. 

Hooda, P. S., Zhang, H., Davison, W., and Edwards, A. C. (1999). Measuringbioavailable trace metals by diffusive gradients in thin films (DGT) Soil moisture effects on its performance in soils. Eur. J. Soil Sri. 50(2), 285-294. 

Recently, attempts have been made to develop biomimetic methods, simulating plant uptake of metals. An example of such a method is DGT (diffusive gradients in thin films), developed by Zhang et al. (2001), for measuring metal availability to plants. In this case, metal accumulation in a chelex layer is measured. By taking into account thickness of the diffusive layer covering the chelex layer and contact time with the soil sample, it is possible to estimate the available metal concentration in the soil solution. The DGT method may also be used to estimate metal speciation in surface water (Zhang 2004). 

The diffusive gradient in thin films (DGT) and Chemcatcher passive samplers provide an alternative approach to monitoring concentrations of heavy metals in water. They measure the labile species, but in addition the DGT can provide information on the other species of an individual metal present in the environment (Gorecki and Namiesnik, 2002 Vrana etal., 2005 van Leeuwen etal., 2005 Guigues et al., 2007). The latter is determined by using two sets of DGT samplers, one with an open pore gel layer, and... 

Chang L-Y, Davidson W, Zhang H, et al. 1998. Performance characteristics for the measurement of Cs and Sr by diffusive gradients in thin films (DGT). Anal Chim Acta 368 243-253. 

Diffusion Gradient in Thin films (DGT) and equilibrium techniques such as Peepers and DETs... 

The use of some other techniques, including electrodialysis, diffusion through membrane, diffusive gradient in thin-film (DGT) (Hooda et al. 2001), and bioindication has also been proposed. However,... 

From these examples, it is clear that diffusion can be a problem under some circumstances. From the palaeolimnologist s perspective, it is important to be able to predict where such problems will occur, and what their potential significance is. A promising approach to this is via modeling. Some hope is also offered by the diffusive gradients in thin-films (DGT) technique (e.g.. Harper et al., 1998), because it may then be possible to estimate at each site the relative mobility of the elements nnder study. 

Diffusive gradient in thin films A technique for measuring trace element availability (a combination of dissolved concentration and diffusive mobility) in sediment using sheets coated with exchange resin. 

Figure 2 Schematic diagram of a DGT sampler designed for water quality monitoring and schematic representation of the free concentration profile of ionic species in the sampler when in contact with an aqueous solution. DBL is the diffusive boundary layer. (Reprinted with permission from Zhang H and Davison W (1995) Performance characteristics of diffusion gradients in thin films of the in situ measurement of trace metals in aqueous solution. Anaiytical Chemistry 67 3391-3400 American Chemical Society.)...

In recent years, novel techniques called diffusive gradient in thin films technique (DGT) were developed for obtaining speciation data and preconcentration of uranium from aqueous samples (Li et al. 2006). The method employs a bottom layer of a binding phase and an upper layer of a permeable hydrogel covered with a filter membrane. The metal ions diffuse through the membrane and upper layer and are captured by the bottom layer that contains a resin embedded in a gel (usually acrylamide), as shown schematically in Figure 3.14 (Gregusova and Docekal 2011). 

Li, W., Zhao, J., Li, C. et al. (2006). Speciation measurements of uranium in alkaline waters using diffusive gradients in thin films technique, Anal. Chim. Acta 575, 274—280. 

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