**14. Impregnated ion exchangers**

The impregnated resins obtained by physically loaded organic reagents on a solid inert support material such as Amberlite XAD resins are an attractive material for separation and preconcentration of heavy metal ions (Prabhakaran & Subramanian, 2003). They are characterized by good porosity, uniform pore size distribution, high surface area as a chemical homogeneous, non-ionic structure. For instance, it was found that Amberlite XAD-2 functionalized with dithiocarbamate ligand, 1,8-dihydroxynaphthalene-3,6-disulphonic acid (chromotropic acid), 2(2-thiazolylazo)-*p*-cresol, l-(2-pyridylazo)-2-naphthol, calmagite, xylenol orange (Abollino et al. 1998; Ferreira & Brito, 1999, Ferreira et al. 1999; Ferreira et al. 2000a; Ferreira et al. 2000b; Tewari & Singh, 1999; Tewari & Singh, 2000; Tewari & Singh, 2001; Tewari & Singh, 2002) can be used for selective sorption and preconcentration of heavy metal ions. Amberlite XAD-4 loaded with sodium diethyl dithiocarbamate; 2,3-dihydroxy benzoic acid (DHBA), ammonium pyrrolidine dithiocarbamate (APDC) and piperidine dithiocarbamate (pipDTC) were used for preconcentration and determination of metal ions in various matrices (Uzun et al. 2001; Hosseini et al. 2006; Ramesh et al. 2002). However, the most promising polymeric support with a larger surface area is Amberlite XAD 16. Amberlite XAD-16 loaded with quercitin (Sharma & Pant, 2009) is characterized by good adsorbent properties for large amounts of uncharged compounds (Tokaloğlu et al. 2010). The solid phase extraction (SPE) process with the application of such materials is characterized by important advantages such simplicity, flexibility, economical, rapid, higher enrichment factors, absence of emulsion and low cost because of lower consumption of reagents.

In general, sorption selectivity of a resin can be affected by both sorbate-sorbent and sorbate-solvent interactions. It has been well recognized that resin matrix and functional groups can strongly affect ion exchange capacity and selectivity. Therefore in the presented paper the chelating ion exchangers Diphonix Resin® containing diphosphonic, sulphonic and carboxylic acid groups and Dowex M 4195 with the bis(2-pyridylmethyl) amine functional group were used for the sorption of Cu(II), Zn(II), Co(II), Pb(II) complexes with Baypure CX 100 (IDS) and Cu(II), Zn(II), Cd(II), Pb(II) complexes with Trilon M (MGDA). The presence of the sulphonic functional groups determines better hydrophilic properties of Diphonix Resin® compared to the traditional monofunctional ion exchangers.
