Synthesis of Bis(amino alcohol)oxalamides and Their Usage for the Preconcentration of Trace Metals by Cloud Point Extraction

C2-Symmetric two bis(amino alcohol)oxalamides (diamidediols) were synthesized and fully characterized. A new method was developed and successfully applied for the simultaneous preconcentration of both trace and toxic metals in water, by using C2-symmetric compounds. Under the optimum experimental conditions (i.e. pH = 10.0 ± 0.2, 2.75 × 10-3 mol L-1 N,N′-bis[(1R)-1-ethyl-2-hydroxyethyl]ethanediamide (DAD1), 1.75 × 10-3 mol L-1 N,N′-bis[(1S)-1-benzyl-2-hydroxyethyl]-ethanediamide (DAD2), 0.10% w/v octylphenoxy-polyethoxyethanol (Triton X-114)), calibration graphs were linear in the range of 2.5 - 25.0 ng mL-1 for Cu and Cd, 5.0 - 25.0 ng mL-1 for Co and Ni. The enrichment factors were 18, 23, 18 and 20 for Cd, Cu, Co and Ni in the case of DAD1, respectively; 20, 22, 17 and 20 for Cd, Cu, Co and Ni in the case of DAD2. The limits of detection for DAD1 were found to be 0.45, 0.50, 1.25 and 0.60 ng mL-1 for Cd, Cu, Co and Ni, respectively, and for DAD2 were found to be 0.44, 0.25, 0.60 and 1.55 ng mL-1 for Cd, Cu, Co and Ni, respectively. The developed method was applied to the determination of Cu, Cd, Co and Ni in water samples and certified reference materials with satisfactory results.