Related Experiment Video
Updated: Jun 25, 2026
12:03
Two-Dimensional Visualization and Quantification of Labile, Inorganic Plant Nutrients and Contaminants in Soil
Published on: September 1, 2020
Metal speciation by DGT/DET in colloidal complex systems
Pascal L R Van der Veeken1, José P Pinheiro, Herman P Van Leeuwen
1Department of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703HB Wageningen, The Netherlands. pascal.vanderveeken@wur.nl
Environmental Science & Technology
|February 6, 2009
Summary
Large colloidal particles can enter gel layers used in DGT (diffusive gradients in a thin film) sensors, challenging assumptions about their exclusion and impacting trace metal speciation analysis in aquatic environments.
Area of Science:
- Environmental Chemistry
- Analytical Chemistry
- Materials Science
Background:
- Gel-layer-based sensors, particularly diffusive gradients in thin film (DGT) devices, are vital for dynamic trace metal speciation in aquatic systems.
- Polyacrylamide hydrogels (
- open pore
- restricted
- ) are standard diffusive layers in DGT, assumed impermeable to colloidal particles.
Purpose of the Study:
- To investigate the permeation of colloidal particles into DGT hydrogel layers.
- To assess the impact of particle size on gel penetration and its implications for trace metal speciation analysis.
Main Methods:
- Complementary use of DGT flux analysis and diffusive equilibration in thin film accumulation.
- Utilizing lead(II) (Pb(II)) as a probe metal and monodisperse latex particles as metal-binding agents.
Main Results:
- Substantial permeation of colloidal particles with radii up to 130 nm into DGT hydrogels was demonstrated.
- Contrary to previous assumptions, relatively large particles significantly enter the gel layers.
Conclusions:
- The findings challenge the established understanding of colloidal exclusion in DGT sensors.
- Re-evaluation of dynamic speciation data interpretation is necessary due to significant particle permeation into gel layers.
More Related Videos
Related Concept Videos
00:56Extraction: Advanced Methods
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is formed in...
01:22EDTA: Chemistry and Properties
Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...
03:45Formation of Complex Ions
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
00:43Complexometric Titration: Ligands
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:19Complexation Equilibria: The Chelate Effect
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...