Evaluating diffusive gradients in thin films (DGT) passive samplers for simultaneous measurement of Platinum, Palladium, Rhodium and Mercury in surface water

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Increasing anthropogenic activity often has detrimental effects on human health and the environment
due to the accompanying emissions of toxic compounds. The increased application of Platinum Group
Elements (PGEs) (Pt, Pd, Rh, Ru, Os and Ir) in the last decades, especially as car catalysts but also in
other applications, makes it necessary to monitor the concentration of these elements in the
environment, investigate their environmental transformations and bioavailability. Mercury (Hg) is also
recognized as one of the most toxic trace elements, whose natural cycle has been altered by
anthropogenic activities. Complex biogeotransformations result in different chemical species, with
varying toxicities and mobility, which need close monitoring. The concentration of these
elements usually extremely low in the aquatic environment, which makes the analysis challenging.
As the toxicity, bioavailability and the cycle of environmental contaminants can strongly be influenced
by their chemical speciation, in recent years, the importance of speciation analysis has been
recognized by the environmental monitoring and assessment community, leading to the development
of an increasing number of speciation techniques. The in situ passive sampling technique diffusive
gradients in thin films (DGT) as a speciation tool is based on the binding of labile metal species on a
resin gel layer via the diffusion through a diffusive hydrogel (agarose or polyacrylamide) using Fick's
Law. The concentration gradient built between the bulk solution and the resin gel makes preconcentration of solutes possible. Using Fick’s law, the time-weighted average concentrations of labile
metal species can be obtained in situ. This technique has been widely used to assess trace elements
such as Cd, Cu, Ni, Pb, Co, Zn in aquatic systems, but never been applied to test PGE elements until
The aim of this study was to develop the DGT technique for the assessment of PGE and Hg using two
novel resins R14 and R20, which were designed specifically for above elements. This implies that the
binding of the PGEs to the resin is strong, irreversible, almost instantaneous and the accumulated
metals amounts are well below the capacity of the resin. The method development involves several
different steps: 1) selection of an appropriate diffusive gel 2) the selection of an appropriate resin or
binding phase for the PGEs and Hg, 3) development of an efficient elution method for the PGEs and Hg
from the resin gel, 4) evaluation of the linear response in function of the deployment time, 5)
determination of diffusion coefficients for the PGEs and Hg in the diffusive gel, 6) study the selectivity
of the tested resins gels, 7) the accumulated metal amount is well below the capacity of the binding
gel, 8) fast kinetics of the resins gels.
Agarose diffusive gel (AGA) (1.5% agarose) was chosen for lower interaction with PGEs and Hg,
adequate blank values and linear response (R2 = 0.99) in function of the time were obtained for the
new resins gels and diffusion coefficients could be determined. An aqua regia and thiourea in
hydrogen chloride elution methods gave a recovery for PGEs and Hg over 90% and 80% for the R20 and
R14 resins gels, respectively. The selectivity test showed these two resins have higher selectivity to PGE
and Hg than other trace elements even though they are at very high concentration level and the
analysis of PGEs and Hg by sector field ICP-MS optimized. The new resin gels showed capability of
accumulation concentration of PGEs and Hg of each hundred times higher than their reported
concentrations in the aquatic environments.
Preliminary deployments in the Zenne River and UZ hospital effluent, Brussels, Belgium, showed that Pt,
Pd, Rh and Hg can be quantified by the DGT technique using both evaluated resins in fresh water.
Keywords: DGT; PGEs; Hg; SF ICP-MS; diffusive coefficient; surface water; speciation
Original languageEnglish
Publication statusPublished - 17 Mar 2017
EventVLIZ Marine Science Day 2017 - VIVES Bruges, Bruges, Belgium
Duration: 3 Mar 20173 Mar 2017


ConferenceVLIZ Marine Science Day 2017
Abbreviated titleVMSD17
Internet address


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