Binary and ternary complexes of epinephrine with alginate and biologically and environmentally relevant metal cations.

The speciation of epinephrine ( ) in the presence of alginate ( ) and two biological and environmental relevant metal cations (Cu, UO ) was investigated at = 298.15K, = 0.15-1.00 mol dm in NaCl. The formation of binary and ternary complexes was evaluated and, since epinephrine can behave as a zwitterion, the / interaction was studied by means of DOSY NMR. The dependence of the equilibrium constants on ionic strength was studied using an extended Debye-Hückel type equation and the SIT approach. The effect of temperature was investigated by means of isoperibolic titration calorimetry: the entropic contribution was the driving force for the Cu/ complexes formation. The sequestering ability of and on Cu, evaluated by the pL calculation, increased with pH and ionic strength. The determination of pM parameter showed that had a higher Cu affinity with respect to . The formation of / species was also investigated by UV-Vis spectrophotometry and H NMR measurements. The ternary Cu/ / and Cu/UO / interactions were also studied. The "extra-stability" calculated for the mixed ternary species confirmed that their formation was thermodynamically favorable.