Comparison of Chelex based resins in diffusive gradients in thin-film for high resolution assessment of metals
In: Talanta. Elsevier: Amsterdam. ISSN 0039-9140; e-ISSN 1873-3573, more
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| Keyword |
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| Author keywords |
Diffusive gradients in thin-film (DGT); Chelex-100; SPR-IDA; Capacity;Ground Chelex-100; High resolution |
| Abstract |
The passive sampling technique of diffusive gradients in thin-film (DGT) is widely used to determine 1D profiles (using Chelex-100 resin) and 2D images (using suspended particulate reagent-iminodiacetate resin, abbreviated as SPR-IDA resin) of metals in sediment pore waters and in oxic/anoxic soils. However, when deployed in anoxic sediments with high metal concentrations, Fe and Mn concentrations determined with the Chelex-100 resin gel were similar to 5 times higher than concentrations measured with the SPR-IDA resin gel. This discrepancy suggests that the SPR-IDA resin gel is saturated faster than the Chelex-100 resin gel. Here, we tested the adsorption capacity of the SPR-IDA resin gel and compared it to the Chelex-100 resin gel. Fe and Mn binding capacities on a SPR-IDA gel disc are less than 0.1 mu moles, which means that they are far below those on a Chelex-100 gel disc (around 3.2 mu moles), while competition with stronger binding metals such as Cu and Cd further lowers Fe and Mn capacities. This restricts the SPR-IDA resin gel to be used in contaminated marine sediments. We propose the use of a ground Chelex-100 resin, which is prepared by grinding Chelex-100 resin in a ball-mill prior to gel preparation. The capacities of Fe and Mn on a ground Chelex-100 resin gel disc are around 1.6 mu moles, more than 16 times higher than the capacity on SPR-IDA gel disc. In addition, the bead size of the ground Chelex-100 resin is small enough (similar to 10 mu m) to allow high resolution LA-ICP-MS imaging of Fe, Mn and trace metals in sediment pore waters as well as soils. |
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