The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with cadmium(II) was studied spectrophotometrically and its kinetic and equilibrium constants were determined. The influence of temperature on the reaction rate was also studied. At different ratios of [CPI][Cd(II)] two types of complex were formed: CdII(CPI) and (CdII)2(CPI); an investigation of the solution properties and the mechanism of aggregation of (CdII)2(CPI) at different pH were performed. It is verified that cadmium(II) accelerates the reaction of the incorporation of manganese(II) into CPI by the substitution of cadmium(II) with manganese(II) in the CdII(CPI) complex; the kinetics and mechanism of this substitution reaction at alkaline pH were studied. A sensitive kinetic method for the determination of cadmium(II) at ppb levels has been established; the molar absorptivity and the Sandell’s sensitivity (for A = 0.001) of the recommended procedure at 458 nm and 300 s after the start of the reaction are (6.175 0.026) 105 1 mol-1 cm-1 and (1.820 0.008) 10-4 mg cm-2 respectively.
Kinetics of the metallation of coproporphyrin-I in water with cadmium(II) and manganese(II)
BARTOCCI, Vito;GIOVANNETTI, Rita;
1998-01-01
Abstract
The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with cadmium(II) was studied spectrophotometrically and its kinetic and equilibrium constants were determined. The influence of temperature on the reaction rate was also studied. At different ratios of [CPI][Cd(II)] two types of complex were formed: CdII(CPI) and (CdII)2(CPI); an investigation of the solution properties and the mechanism of aggregation of (CdII)2(CPI) at different pH were performed. It is verified that cadmium(II) accelerates the reaction of the incorporation of manganese(II) into CPI by the substitution of cadmium(II) with manganese(II) in the CdII(CPI) complex; the kinetics and mechanism of this substitution reaction at alkaline pH were studied. A sensitive kinetic method for the determination of cadmium(II) at ppb levels has been established; the molar absorptivity and the Sandell’s sensitivity (for A = 0.001) of the recommended procedure at 458 nm and 300 s after the start of the reaction are (6.175 0.026) 105 1 mol-1 cm-1 and (1.820 0.008) 10-4 mg cm-2 respectively.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
