Perfluorosulfonated Ionomer-Modified Diffusive Gradients in Thin Films: Tool for Inorganic Arsenic Speciation Analysis

Abstract

A new concept in speciation analysis based on the diffusive gradients in thin films (DGT) technique is described. By use of two sets of DGT devices, one set with perfluorosulfonated ionomer (Nafion) diffusive membranes and the other with polyacrylamide, anionic and uncharged analytes can be fractionated on the basis of charge. The dual device method is applied to speciation analysis of dissolved inorganic arsenic species. Over the environmentally significant pH range, inorganic As(III) exists as neutral H(3)AsO(3), whereas As(V) is present as anionic H(2)AsO(4)(-) and HAsO(4)(2-). The measured diffusion coefficient of As(III) through the negatively charged Nafion membrane is significantly larger than that of the As(V) species, whereas diffusion rates are similar through polyacrylamide diffusive gels. Hence, after simultaneously deploying DGT devices with and without Nafion membranes, measurement of the amount of accumulated As in each type of device enables the concentration of both oxidation states to be determined.

A systematic determination of diffusion coefficients of trace elements in open and restricted diffusive layers used by the diffusive gradients in a thin film technique

“…This retardation of oxyanions relative to cations is interesting and consistent with the presence of a negative charge on the polyacrylamide hydrogels. Such an effect was used deliberately by Panther et al [31] who impeded diffusion of arsenate anions with a negatively charged Nafion membrane, relative to neutral As(III) species. Acrylamide functional groups are known to undergo partial hydrolysis to acrylic acid groups which are negatively charged when deprotonated [32].…”

Determination of total arsenic using a novel Zn-ferrite binding gel for DGT techniques: Application to the redox speciation of arsenic in river sediments

“…As(III) is also determined with binding gels sensitive to total As species but covered with an anionic membrane barrier (e.g. Nafion membrane) inhibiting the diffusion of anionic species in the range of pH 3-7 [15]. The determination of total As content is possible from several binding gels with a binding agent such as ferrihydrite [16], Metsorb s HMRP 50 [17], ZrO [18].…”

Diffusive gradients in thin films: devices, materials and applications

“…A series of materials have been applied as the diffusive gel in DGT (Table 3), including agarose cross-linked polyacrylamide (APA) gel (Shiva et al 2017;Zhang and Davison 1995), agarose gel (Colaço et al 2012;Docekalova and Divis 2005;Wang et al 2016), dialysis membranes (Li et al 2003), nylon membranes (Panther et al 2008) and paper-based diffusion layer, such as 3MM chromatographic paper (de Almeida et al 2012; de Oliveira et al 2012) as well as chromatography paper grade 1 Chr and 17 Chr (Larner and Seen 2005).…”