Thermodynamic data for Pb²⁺and Zn²⁺sequestration by biologically important S-donor ligands, at different temperatures and ionic strengths

Abstract

A thermodynamic picture is reported for cys–Pb2+, psh–Pb2+, gsh–Pb2+, and gsh–Zn2+systems, and equilibrium constants can be predicted for any experimental condition.

Lead(II) Binding to the Chelating Agent d-Penicillamine in Aqueous Solution

“…When using the most recent formation constants obtained by Crea et al ( I = 0.1 M), 31 the best value estimated for the solubility product for PbPen(c) matching our experimental observations (i.e., the pH at which PbPen(c) dissolved under different ligand concentrations) was log K sp = −16.2. Also according to the diagrams shown in Figure S-2b in the Supporting Information , solutions A and A* are dominated by [Pb(Pen) 2 ] 2– , but with a minor amount of another type of hydroxo complex being present, i.e., [Pb(OH)(Pen)] − .…”

“…The loss of peak intensity at 298 nm for solution A (Figure 2 ) could be due to a minor amount of other Pb(II) species with a smaller number of coordinated thiolate groups, such as [Pb(Pen)(OH)] − , as suggested by Crea et al 31 Considering the high formation constant (log β 1 = 13.37–14.32) for the Pb:Pen 1:1 complex, 30 , 31 solution A does not contain hydrolyzed Pb(II) species (see Figures S-1b and S-2b in the Supporting Information ), such as Pb(OH) 3 – (aq) (log β = −26.5, I = 1 M NaClO 4 ), for which λ max = 239 nm (ε max ≈ 2500 M –1 cm –1 ) has been reported. 63 …”

“… 30 More recently, Crea and co-workers also reported a new set of formation constants based on potentiometric measurements for PbPen, [Pb(HPen)] + , [Pb(H 2 Pen)] 2+ , [Pb(Pen) 2 ] 2– , and [Pb(Pen)(OH)] − (0.5 ≤ C H 2 Pen ≤ 2.0 mM, C Pb(II) = 0.5 mM, pH = 2.5–10.5, 0 < I ≤ 1.0 M NaNO 3 , 25 °C); see Figure S-2a in the Supporting Information . 31 At such low concentrations, no PbPen(c) precipitation was observed, and there is no solubility product/formation constant reported for this solid.…”

Lead(II) Complex Formation with l-Cysteine in Aqueous Solution

“…(ionic strength I = 1.0 M) and Crea et al (0 < I < 1.0 M), 16, 20 show mixtures of monomeric PbCys, Pb(OH)(Cys) − , Pb(Cys) 2 2− and/ or Pb(HCys)(Cys) − species in alkaline solutions (Figures S-1a and S-2a). At higher concentrations, such as in the current study, PbCys(c) precipitates within a wide pH range.…”

Assessing the Quality of Milk Using a Multicomponent Analytical Platform MicroNIR/Chemometric

“…For this reason, innovative screening systems, able to rapidly process samples without requiring any pretreatment or clean up, in a non-destructive way, are becoming more and more recommended (Dunn et al, 2011 ; Risoluti et al, 2016 , 2019a , b , c ; D'Elia et al, 2018 ). Reference analytical procedures for milk analyses usually require chromatographic techniques, such as High Performance Liquid Chromatography associated to Mass Spectrometry (HPLC-MS) (Chotyakul et al, 2014 ; Aiello et al, 2015 ; Rocchetti et al, 2020 ), Gas Chromatography coupled to Mass Spectrometry (GC-MS) (Marchetti et al, 2002 ; Materazzi and Risoluti, 2014 ; Teng et al, 2017 ), and Nuclear Magnetic Resonance (NMR) (Garcia et al, 2012 ; Crea et al, 2014 ; Santos et al, 2016 ; Aiello et al, 2018 ).…”