The speciation measurements of trace metals by the diffusive gradients in thin-films technique (DGT) using a poly(4-styrenesulfonate) (PSS) aq. soln. as a binding phase and a cellulose dialysis membrane (CDM) as a diffusive layer, CDM-PSS DGT, were studied and showed good agreement with computer modeling calcns. The diffusion coeffs. of EDTA complexes with Cd2+ and Cu2+ were measured and compared with those of the inorg. metal ions. CDM-PSS DGT device was tested for speciation measurement in sample solns. contg. EDTA, tannic acid (TA), glucose (GL), dodecylbenzenesulfonic acid (DBS) and humic acid (HA) as complexing ligands forming org. complexes with varying stability consts. Lower percentages of DGT labile Cu concns. over total filterable Cu concns. obtained from the deployments in freshwater sites indicated that Cu complexes with org. matter were basically not measured by the devices.