Bretti Clemente, Cardiano Paola, Irto Anna, Lando Gabriele, Milea Demetrio, Sammartano Silvio
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale Ferdinando Stagno d'Alcontres 31, 98166 Messina, Italy.
J Mol Liq. 2020 Dec 1;319:114164. doi: 10.1016/j.molliq.2020.114164. Epub 2020 Aug 29.
The estimation of thermodynamic parameters of N-Acetyl-L-cysteine (NAC) protonation were determined in NaCl, (CH)NCl, (CH)NI employing various temperature and ionic strengths conditions, by potentiometric measurements. The interaction of NAC with some essential metal cations (, Ca, Mg and Zn) was investigated as well at 298.15 K in NaCl in the ionic strength range 0.1 ≤ /mol dm ≤ 1.0. The values of protonation constants at infinite dilution and at = 298.15 K are: log = 9.962 ± 0.005 (S-H) and log = 3.347 ± 0.008 (COO-H). In the presence of a background electrolyte, both log and log values followed the trend (CH)NI ≥ (CH)NCl ≥ NaCl. The differences in the values of protonation constants among the three ionic media were interpreted in terms of variation of activity coefficients and formation of weak complexes. Accordingly, the determination of the stability of 4 species, namely: NaL, NaHL , (CH)NL, (CH)NHL was assessed. In addition, as regards the interactions of Mg, Ca and Zn with NAC, the main species where the ML , ML(OH), and ML , that were found to be important in the chemical speciation of NAC in real multicomponent solutions. The whole set of the data collected may be crucial for the development of NAC-based materials for natural fluids selective decontamination from heavy metals.
通过电位测量法，在不同温度和离子强度条件下，于氯化钠、（CH）NCl、（CH）NI中测定了N-乙酰-L-半胱氨酸（NAC）质子化的热力学参数。在298.15 K下，于离子强度范围为0.1≤/mol dm≤1.0的氯化钠溶液中，还研究了NAC与一些必需金属阳离子（、钙、镁和锌）的相互作用。在无限稀释且=298.15 K时，质子化常数的值为：log = 9.962±0.005（S-H），log = 3.347±0.008（COO-H）。在存在背景电解质的情况下，log和log值均遵循（CH）NI≥（CH）NCl≥NaCl的趋势。三种离子介质中质子化常数的差异，根据活度系数的变化和弱配合物的形成进行了解释。因此，评估了四种物种，即：NaL、NaHL、（CH）NL、（CH）NHL的稳定性。此外，关于镁、钙和锌与NAC的相互作用，发现主要物种ML、ML（OH）和ML在实际多组分溶液中NAC的化学形态中很重要。所收集的整套数据对于开发用于从重金属中选择性净化天然流体的基于NAC的材料可能至关重要。
