Stability constants of the ternary complexes of CuDTPA, NiDCTA, CrEDTA, CoHEEDTA, NiHEEDTA and CuHEEEDT Aheedta with OH-.
The acid dissociation constants of the metal chelates H(3)CuDTPA, H(2) NiDCTA, HCrEDTA, HCoHEEDTA, HNiHEEDTA and HCuHEEDTA were determined by potentiometric titration. The constants determined at an ionic strength of 0.1 were pK(a,1) = 2.1; pK(a,2) = 2.8 and pK(a,3) = 4.75 for H(3) CuDTPA (296 K), pK(a,1) = 2.16 for HCrEDTA (298 K); pK(a,1) = 1.6 and pK(a,2) = 2.0 for H(2) NiDCTA (298 K); pK(a,1) = 2.24 for HCoHEEDTA, pK(a,1) = 2.47 for HCuHEEDTA and pK(a,1) = 1.73 for HNi-HEEDTA. At high pH the formation of ternary hydroxo-complexes was observed for the chelates CrEDTA(-) (pK(a,1) = 7.35; pK(a,1) = 12.35), CoHEEDTA(-) (pK(a,1) = 11.74), NiHEEDTA(-) (pK(a,2) = 12,44) and CuHEEDTA(-) (pK(a,2) = 10.45).
Korsse
J
J
National Institute for Nuclear and High-Energy Physics (NIKHEF, section K), P.O. Box 4395, 1009 AJ Amsterdam, The Netherlands.
Leurs
G A
GA
Louwrier
P W
PW