Mixed-mode ion-exchange polymeric sorbents: dual-phase materials that improve selectivity and capacity

In this article, we describe mixed-mode polymeric sorbents, which, in a single material, enhance the selectivity and the capacity of the extraction process. We have structured the article around the four types of mixed-mode sorbents (i.e. strong/weak and cation/anion-exchange materials). We cover different aspects of these materials, starting with a proper understanding of their morphological and chemical properties, so that the appropriate sorbent can be selected for each particular case. We deal with another important issue the solid-phase extraction protocol recommended for each type of sorbent to enhance its specific properties. We also provide a list of all the mixed-mode polymeric sorbents both commercially available and prepared in-house. Finally, we discuss the leading applications of the types of analytes and the matrices extracted using these materials and illustrate them with selected examples. (C) 2010 Elsevier Ltd. All rights reserved.