The formation constants of species formed in the systems H +-Zn 2+-cysteine and H +-Zn 2+-cystine have been determined in aqueous solution at 37° and I = 0.15 mot dm -3 (NaClO 4), using the pH-metric method. The existence of the following species [ZnL], [ZnL 2], [ZnL 2H] and [Zn 2L 3] (2.3 ≤pH ≤ 7.7) was proved for the Zn 2+-cysteine system, whereas for the Zn 2+-cystine [Zn 2L] (5.3 ≤ pH ≤ 6.4) was the only species found. In the Zn 2+-cystine system the pH range was severely restricted because of precipitation occurring at pH > 6.4. A new experimental and numerical approach was employed in order to implement the possibility of rigorously selecting the species present in each system. The results have been compared with data previously reported on the same systems, considering in particular the different sets of species found in the various works.
Zinc(II)Cysteine and Zinc(II)Cystine Systems: Selection of Species from Potentiometric Data.
SAMMARTANO, Silvio;
1980-01-01
Abstract
The formation constants of species formed in the systems H +-Zn 2+-cysteine and H +-Zn 2+-cystine have been determined in aqueous solution at 37° and I = 0.15 mot dm -3 (NaClO 4), using the pH-metric method. The existence of the following species [ZnL], [ZnL 2], [ZnL 2H] and [Zn 2L 3] (2.3 ≤pH ≤ 7.7) was proved for the Zn 2+-cysteine system, whereas for the Zn 2+-cystine [Zn 2L] (5.3 ≤ pH ≤ 6.4) was the only species found. In the Zn 2+-cystine system the pH range was severely restricted because of precipitation occurring at pH > 6.4. A new experimental and numerical approach was employed in order to implement the possibility of rigorously selecting the species present in each system. The results have been compared with data previously reported on the same systems, considering in particular the different sets of species found in the various works.Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
