Polymer-supported reagents are widely employed in the complexation of metal ions for applications in separations science, organic reactions (as catalysts) and in analytical chemistry (for processes requiring metal ion enrichment, detection and quantification). Various strategies for the continued development and optimization of polymer-supported reagents have evolved. This review cites ways in which polymer-supported reagents can be designed to achieve improved metal ion selectivities from the viewpoint of the mechanisms involved in the complexation of transition metal ions from aqueous solutions. (C) 2010 Elsevier Ltd. All rights reserved.