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This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by ?-ED-XRF mapping on selected samples.

The archaeological excavations at Villa San Pancrazio (Taormina, Italy) are bringing to light a vast Roman-Imperial residential quarter featuring luxurious dwellings decorated with wall paintings and mosaic floors, pointing it out as one of the most significant archaeological sites of the city. The polychrome and black and white mosaics recovered date back to the middle Imperial period, during the 2nd century AD. This work deals with the first archaeometric investigations of the materials employed for the tesserae production with the aim of elucidating the mineralogical composition and obtaining analytical evidence that can contribute to extracting information related to their production technology. For that purpose, a non-invasive methodology, based on micro energy dispersive X-ray fluorescence (μ-EDXRF) spectrometry and Raman spectroscopy, was used to characterize a wide selection of stone, ceramic and glass tesserae. Chemometric tools were exploited to manage the large set of elemental data collected on black and white lithic samples, providing essential clues for the subsequent investigations. The results evidenced the employment of natural lithotypes (calcareous sedimentary, dolomitic and volcanic) local and imported, and also artificial materials, such as ceramic made firing magnesium-rich clays, soda-lime-silica glasses made with different opacifying and coloring agents (such as calcium antimoniate, cobalt and copper) This work was supported by project IT-742-13 for Consolidated Research Groups, funded by the Basque Country Government. P. Irizar gratefully acknowledges his predoctoral grant (PRE2018-085888) from the MINECO Spanish Ministry. O. Gómez-Laserna is grateful to the University of the Basque Country (UPV/EHU) for her postdoctoral contract. P. Cardiano also thanks University of Messina (FFABR UNIME 2020) for funding.

Purpose To assess the effectiveness and safety of intravenous (IV) dexmedetomidine for sedation in ophthalmic surgery. Methods Prospective, observational, uncontrolled, single-center study. Patients were sedated with a continuous dexmedetomidine IV infusion started 15 min before regional anesthesia administration and maintained up to the end of surgery. Effectiveness of dexmedetomidine was assessed by the Modified Observer's Assessment of Alertness and Sedation (MOAA/S) targeted at 5. Safety was assessed by the incidence of patients’ movements/snoring and by the incidence of respiratory and haemodynamic complications. An eleven-point numerical rating scale (NRS) was used to assess the level of satisfaction of both the surgeon and the patient. Results 123 patients (73 males, mean age: 63 ± 13) were included; 81 (81/123; 65.8%) patients reached the requested MOAA/S score of 5. Any intraoperative movement – mostly voluntary – occurred in 34 (34/123; 27.6%) cases with no need for a switch to general anaesthesia; no ocular complications related to the intraoperative movements occurred. Intraoperative snoring occurred in 30 (30/123; 24.4%) patients and it did not affect the surgical manoeuvres. Respiratory drive depression requiring manual or mechanical ventilation never occurred. Bradycardia occurred in 14 (14/123; 11.3%), cases but only 4 (4/123; 3.2%) patients required atropine administration, which was always effective. Intraoperative analgesia was consistently obtained and both the surgeons and the patients reported a high NRS satisfaction score. Conclusion Dexmedetomidine provided adequate sedation in patients undergoing ocular surgery under local anaesthesia and showed a good effectiveness and safety profile. Upper airway obstruction, apnoea and snoring can occur.

Protonation of nicotinic acid has been investigated by means of potentiometric titrations at different temperatures 283.15 ≤ T (K) ≤ 383.15 and ionic strengths of NaCl(aq), 0.12 ≤ I (mol·kg−1) ≤ 4.84 and mixed NaCl with MgCl2 or CaCl2. Stability constants of the CaL+ and MgL+ species were obtained by means of the ΔpK method. Different models (e.g. Debye–Huckel type equation, Specific Ion Interaction Theory, Pitzer and van’t Hoff) were applied to account for the ionic strength and temperature dependences, in order to obtain data in a standard state and parameters to calculate stability constants in any point of our experimental domain. Speciation studies were performed simulating the conditions of natural fluids. Literature data were investigated for comparison with the experimental results here obtained.

Epoxy–silica hybrids (i.e., as such, enriched with TiO2 and cerium-doped TiO2 nanoparticles), based on a bisphenol (BPA)-free cycloaliphatic precursor, were designed for potential applications as stone conservation multifunctional materials. To this aim, nanoparticles were specifically prepared and their suitability for incorporation into the hybrids was assessed by means of X-ray diffraction (XRD), BET porosimetry, and photocatalytic activity measurements. On the other hand, the organic-inorganic materials, both undoped and doped with nanoparticles, were sol-gel synthesized in methanol starting from 1,4-cycloexanediglycidyether (CHDM-DGE) and 1,8-diaminooctane (DAO), in the presence of silica-forming additives, such as 3-glycidyloxypropyltrimethoxysilane (GPTMS), tetraethyl orthosilicate (TEOS), and isobuthyl (trimethoxy) silane (iBuTMS). A multianalytical methodology was employed for material characterization. The homogeneity, the extent of the epoxy cleavage, and the absence of partially hydrolyzed Si (OR)3 groups in the cross-linked hybrid networks were established thanks to a combination of scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS), and imaging Raman analysis. Moreover, the thermal, hydrophobic, and chromatic properties of the hybrids were investigated by thermogravimetry/differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), contact angle, and color measurements. Finally, the antimicrobial characterization was studied using a sowing strain of Gram-positive bacteria. The results showed that, among all, one of the epoxy–silica hybrid formulations features some of the main prerequisites to be fulfilled for a successful stone conservation treatment.

The experimental determination of water solubility (log S0) and Setschenow coefficient (km) of a compound is a time-consuming activity, which often needs large amounts of expensive substances. This work aims at establishing two “open-source” chemometric models based on a regression tree that is able to predict the two abovementioned quantities. The dataset used is the largest to appear up to now for the collection of km values, containing information on 295 molecules and it is relevant also for the collection of logS0 values (321 molecules); for each of them 32 descriptors were taken from freely available databases. Information about water solubility and Setschenow coefficients, necessary to train the models, were taken from available literature. Validation was performed on a separate test set of molecules. The precision reached in the prediction is fully satisfying, being RMSEP = 0.6086 and 0.0441 for logS0 and km, respectively.

This work is focused on the design and preparation of polymer inclusion membranes (PIMs) for potential applications for stannous cation sequestration from water. For this purpose, the membranes have been synthesized employing two polymeric matrices, namely, polyvinylchloride (PVC) and cellulose triacetate (CTA), properly enriched with different plasticizers. The novelty here proposed relies on the modification of the cited PIMs by selected extractants expected to interact with the target cation in the membrane bulk or onto its surface, as well as in the evaluation of their performances in the sequestration of tin(II) in solution through chemometric tools. The composition of both the membrane and the solution for each trial was selected by means of a D-Optimal Experimental Design. The samples such prepared were characterized by means of TG-DTA, DSC, and static contact angles investigations; their mechanical properties were studied in terms of tensile strength and elastic modulus, whereas their morphology was checked by SEM. The sequestering ability of the PIMs toward stannous cation was studied by means of kinetic and isotherm experiments using DP-ASV. The presence of tin in the membranes after the sequestration tests was ascertained by μ-ED-XRF mapping on selected samples.

8-hydroxyquinoline-2-carboxylic acid (8-HQA) has been found in high concentrations (0.5&ndash, 5.0 mmol&middot, dm&minus, 3) in the gut of Noctuid larvae (and in a few other lepidopterans), in which it is proposed to act as a siderophore. Since it is known that many natural siderophores are also involved in the uptake and metabolism of other essential elements than iron, this study reports some results on the investigation of 8-HQA interactions with molybdate (MoO42&minus, i.e., the main molybdenum form in aqueous environments), in order to understand the possible role of this ligand as molybdophore. A multi-technique approach has been adopted, in order to derive a comprehensive set of information necessary to assess the chemical speciation of the 8-HQA/MoO42&minus, system, as well as the coordination behavior and the sequestering ability of 8-HQA towards molybdate. Chemical speciation studies have been performed in KCl(aq) at I = 0.2 mol&middot, 3 and T = 298.15 K by ISE-H+ (glass electrode) potentiometric and UV/Vis spectrophotometric titrations. CV (Cyclic Voltammetry), DP-ASV (Differential Pulse-Anodic Stripping Voltammetry), ESI-MS experiments and quantum mechanical calculations have been also performed to derive information about the nature and possible structure of species formed. These results are also compared with those reported for the 8-HQA/Fe3+ system in terms of chemical speciation and sequestering ability of 8-HQA.

The estimation of thermodynamic parameters of N-Acetyl-L-cysteine (NAC) protonation were determined in NaCl(aq), (CH3)4NCl(aq), (C2H5)4NI(aq), employing various temperature and ionic strengths conditions, by potentiometric measurements. The interaction of NAC with some essential metal cations (e.g., Ca2+, Mg2+ and Zn2+) was investigated as well at 298.15 K in NaCl(aq) in the ionic strength range 0.1 ≤ I/mol dm−3 ≤ 1.0. The values of protonation constants at infinite dilution and at T = 298.15 K are: log K1H = 9.962 ± 0.005 (S—H) and log K2H = 3.347 ± 0.008 (COO-H). In the presence of a background electrolyte, both log K1H and log K2H values followed the trend (C2H5)4NI ≥ (CH3)4NCl ≥ 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−, NaHL0(aq), (CH3)4NL−, (CH3)4NHL0(aq) was assessed. In addition, as regards the interactions of Mg2+, Ca2+ and Zn2+ with NAC, the main species where the ML0(aq), ML(OH)−, and ML22−, 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., Graphical abstract Unlabelled Image, Highlights • Interaction of N-Acetyl-L-cysteine with H+, Na+, Ca2+, Mg2+ and Zn2+ is studied. • Data are modeled according to SIT and weak interaction models. • Complexation occurs through sulfur and oxygen. • Speciation of Zn2+ in sea water and blood plasma is proposed. • Results aid in the design of new materials to remove pollutants from natural fluids.

The interactions of epinephrine ((R)-(&minus, )-3,4-dihydroxy-&alpha, (methylaminomethyl)benzyl alcohol, Eph-) with different toxic cations (methylmercury(II): CH3Hg+, dimethyltin(IV): (CH3)2Sn2+, dioxouranium(VI): UO22+) were studied in NaClaq at different ionic strengths and at T = 298.15 K (T = 310.15 K for (CH3)2Sn2+). The enthalpy changes for the protonation of epinephrine and its complex formation with UO22+ were also determined using isoperibolic titration calorimetry: HHL = -39 &plusmn, 1 kJ mol-1, HH2L = -67 &plusmn, 1 kJ mol-1 (overall reaction), HML = -26 &plusmn, 4 kJ mol-1, and HM2L2(OH)2 = 39 &plusmn, 2 kJ mol-1. The results were that UO22+ complexation by Eph- was an entropy-driven process. The dependence on the ionic strength of protonation and the complex formation constants was modeled using the extended Debye&ndash, H&uuml, ckel, specific ion interaction theory (SIT), and Pitzer approaches. The sequestering ability of adrenaline toward the investigated cations was evaluated using the calculation of pL0.5 parameters. The sequestering ability trend resulted in the following: UO22+ &gt, &gt, (CH3)2Sn2+ &gt, CH3Hg+. For example, at I = 0.15 mol dm-3 and pH = 7.4 (pH = 9.5 for CH3Hg+), pL0.5 = 7.68, 5.64, and 2.40 for UO22+, (CH3)2Sn2+, and CH3Hg+, respectively. Here, the pH is with respect to ionic strength in terms of sequestration.

Solution thermodynamics of three aminophosphonic acids are studied in this work. In particular, the protonation constants [ log ( K i H /mol kg−1)] of N-phosphonomethyliminodiacetic acid (NTAP), N,N-Bis(phosphonomethyl)glycine (NTAP2) and Nitrilotris(methylenephosphonic acid) (NTAP3) and the solubility of NTAP were determined by potentiometric measurements (ISE-[H+] glass electrode) in three different ionic media, namely NaCl(aq), (CH3)4NCl(aq) and (C2H5)4NI(aq) at different ionic strengths (in the range 0 log K i H on ionic strength and temperature was studied by Debye-Huckel type equation and by Specific ion Interaction Theory (SIT). At infinite dilution, the refined values of the first protonation constants are: log ( K i H /mol kg−1) = 11.4 ± 0.1, 12.4 ± 0.1 and 13.3 ± 0.1 for NTAP, NTAP2 and NTAP3, respectively and the enthalpy changes relative to the first protonation step are: −15.7 ± 0.3, −20.5 ± 0.4 and –33.5 ± 0.2 kJ mol−1 (same order). The basicity trend: NTAP3 > NTAP2 > NTAP is observed in all the ionic media. The differences in the values of the protonation constants obtained in the three ionic media were also interpreted in terms of formation of weak complex and eleven Na+/L species are obtained using the so called ΔpK method. Solubility investigations performed on NTAP allowed us to determine the Setschenow and the activity coefficients of the neutral species. The values of the total and specific solubility in pure water are: log ( S 0 T /mol kg−1) = −1.431 ± 0.003 and log ( S 0 0 /mol kg−1) = −2.293 ± 0.006, respectively. The formation constants of the three ligands with Ca2+ and Mg2+ cations were determined at T = 298.15 K in NaCl(aq) at I = 0.151 mol kg−1, finding the presence of the ML and MHL species. The stability of the Ca2+/L is slightly higher than that of the Mg2+/L ones.

In this paper, potentiometry and calorimetry were used to determine the thermodynamics of interaction between risedronate and four bivalent metal cations, namely: Mg2+, Zn2+, Pb2+, and Cu2+ in aqueous NaCl solutions at different ionic strengths and at T = 298.15 K. The data analysis allowed us to ascertain that the main species formed were the MLH2, MLH, ML and M2L; however scarcely soluble species precipitated at acidic pH values, between 4 and 7 depending on the metal cation involved, probably due to the formation of the neutral M2L(s) species. Comparison of the stability constants with other similar ligands suggests that metal complexation occurs through the phosphonate with an additional stabilizing contribution due to the pyridine moiety. The dissection of the free energy term revealed that the entropic change is the main contribution to the stability of the complexes for all equilibria, except those regarding the formation of the M2L species, and the main forces involved in these processes are entropic in nature, such as the desolvation of both the ligand and the metal cations. The sequestering ability was evaluated computing the pL0.5 parameter at different pH and ionic strength values; the highest ones were found for Cu2+ in acidic solutions and at low ionic strength, whereas pL0.5 values for both Pb2+ and Zn2+ were slightly lower. Results reported in this work may be helpful in the assessment of the use of risedronate as effective chelating agent and for understanding the mechanism of action of this molecule as a drug.

The speciation of Al3+ in aqueous solutions containing organic and inorganic ligands important from a biological (citrate (Cit3-), gluconate (Gluc-), lactate (Lac-), silicate (H2SiO42-), carbonate (CO32-), fluoride (F-)) and industrial (Gantrez®; polymethyl-vinyl-ether-co-maleic acids; GTZ S95 and GTZ AN169) point of view is reported. The stability constants of Al3+/Lz- complexes (Lz- = ligand with z- charge) were determined by potentiometry at T = 298.15 K and 0.10 ≤ I/M ≤ 1.00 in NaCl(aq) (in NaNO3(aq) only for Al3+/GTZ S95 and Al3+/Gluc- acid systems). For Al3+/Cit3-, Al3+/Lac- and Al3+/GTZ AN1694- systems, the investigations were also carried out at 283.15 ≤ T/K ≤ 318.15. The dependence of the thermodynamic parameters on ionic strength and temperature was modelled with a Debye-Huckel type equation. Different speciation schemes of Al3+/Lz- systems were obtained, including protonated, simple metal-ligand, polynuclear and hydrolytic mixed species. At I → 0 M and T = 298.15 K the stability trend for the AlL(3-z) species is: 14.28 ± 0.02, 13.99 ± 0.03, 10.16 ± 0.03, 3.16 ± 0.08, 2.84 ± 0.10 for GTZ S95, GTZ AN169, Cit3-, Gluc- and Lac-, respectively. From the investigations at different temperatures, it results that the entropic contribution is the driving force of the reactions. The sequestering ability of the ligands towards Al3+ was investigated determining the pL0.5 parameter at different experimental conditions, finding the following trend: Cit3- » Gluc- > GTZ S954- > GTZ AN1694- > Lac- for the organic ligands, and pL0.5: F- » CO32- > H2SiO42- for the inorganic ones.

A potentiometric study on the acid–base properties and formation of complexes with alkali metals (i.e., Na+ and K+) of some poly(methyl vinyl ether-co-maleic) acids, namely, Gantrez AN169 (2000 kDa), S95 (220 kDa), and S97 (1200 kDa), was carried out under different experimental conditions consisting of the ionic medium, ionic strength, and temperature. Owing to the possible formation of micelles, the critical micelle concentration of Gantrez AN169 was determined by means of different techniques in pure water and at T = 298.15 K. The diprotic-like model was used for the elaboration of the experimental protonation data, and the best model was obtained by assuming that a monomeric unit consists of two methyl vinyl ether-co-maleic acid residues. Moreover, the protonation data of two poly(acrylic comaleic acids), PCA 3 kDa and 70 kDa (published in a previous paper), under different experimental conditions were reanalyzed. The trend in the protonation constants of polyelectrolytes in different ionic media is (...

This work is focused on the determination of the thermodynamic parameters of interaction between a biodegradable complexone, as MGDA (methylglycinediacetic acid), towards the major constituents of natural fluids, such as H+, Na+, K+, Ca2+ and Mg2+. The determination of their thermodynamic parameters of interaction was performed by potentiometric and calorimetric measurements in different experimental conditions, in order to determine the protonation and complex formation constants, together with the relative enthalpy changes of reaction. The protonation data were modeled as a function of ionic strength to obtain data in standard conditions using the EDH (extended Debye-Huckel type equation) and the SIT (Specific ion Interaction Theory) approaches. Ionic strength dependence parameters were obtained, enabling the calculation of the equilibrium constants at any value within the ionic strength range here considered (0 The species determined for the Ca2+ and Mg2+/MGDA (defined below as L) systems, namely the ML, MLH and M2L. For Na+, K+ and (CH3)4N+, the M2L species was not determined, but the neutral MH2L was found for Na+ and K+. The stability trend is: Mg2+ > Ca2+ >> Na+ > K+ > (CH3)4N+. In all cases, the experimental data determined show that the stability of all the complex species decreases with increasing the ionic strength. The studies conducted in this work have shown that the MGDA is an effective chelating agent, with a capacity for mobilization comparable with that of NTA. The values of the enthalpy changes are negative, indicating an exothermic reaction for the first and the second protonation step and for the formation of the CaL− species. On the contrary, the third protonation step and the formation reaction of the MgL− species is endothermic. The entropic contribution to the stability of the species was found to be predominant, except for the first protonation constant. Two “case studies” were conducted to evaluate the possible use of MGDA in real systems, the first representing a water for industrial use and second a urine with presence of precipitated calcium oxalate.

Some thermodynamic properties of levulinc acid (LA) were studied under different experimental conditions. The partition coefficient between 2-methyl-1-propanol/pure water (or NaCl aqueous solutions up to I = 1.00 mol dm−3) was measured at T = 298.15 K by means of potentiometric titrations. The protonation constant of levulinic acid was also determined potentiometrically at different ionic strengths in NaCl(aq), (C2H5)4NI(aq) as well as in mixed MgCl2/NaCl and CaCl2/NaCl aqueous solutions. The protonation enthalpy was determined by calorimetric titrations in the same conditions of temperature and ionic strength. The linear fitting of the distribution ratio (log KD) determined at different salt concentrations vs. the salt concentration allowed for the determination of the distribution coefficient at infinite dilution ( log K D0 0 = −0.14 ± 0.02), the Setschenow (km = 0.35 ± 0.03) and the activity coefficient of the neutral species (log γHL = km·msalt). The activity coefficient of the charged L− species was also computed by means of the Specific Interaction Theory (SIT) approach by keeping constant the value of the activity coefficient for the neutral HL species. The medium effect on the protonation constant was also studied using the weak interaction model, namely by comparing the protonation constants obtained in NaCl(aq), (C2H5)4NI(aq) as well as in mixed aqueous MgCl2/NaCl and CaCl2/NaCl mixtures by considering the formation of a NaL(aq), CaL+(aq), and MgL+(aq) species.

This work is focused on the development of sustainable stone conservation materials, based on BPA-free epoxy-silica hybrid resins, with consolidating and hydrophobic properties, for long-term treatments. For this purpose, a cycloaliphatic diol, with minor health and environmental associated issues with respect to classic phenolic derivatives, was selected to synthesize a BPA-free bio-based epoxy resins precursor, 2,2,4,4-tetramethyl-1,3-cyclobutanediol diglycidylether (CBDO-DGE). Fourier transform infrared (FT-IR) and Raman spectroscopies were employed to assess the synthesis and clean-up procedures. In addition, both 1H-NMR and 13C-NMR in solution were used to ascertain the structure and purity of the bio-based epoxy. The development of the epoxy thermosets by 1,8- diaminooctane (DAO), triethylenetetramine (TETA) and 5-amino-1,3,3-trimethylcyclohexanemethylamine (IPDA) curing agents was followed by attenuated total reflection infrared (ATR FT-IR) and Raman spectroscopies, whereas their suitability as organic counterpart of the hybrids was established by differential scanning calorimetry (DSC) and thermogravimetric (TGA) measurements. In addition, epoxy-silica hybrids were obtained by exploiting sol-gel technology, carrying out the epoxy hardening reactions also in the presence of (3-glycidyloxypropyl)trimethoxysilane (GPTMS) and octyltriethoxysilane (OcTES), as silica-forming additives. To investigate the properties of the resulting hybrid materials imparted by the selection of the different reactants, various blends were studied by a combination of scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS), ATR FT-IR and Raman analysis. Furthermore, the assessment of the hybrids tunability as materials for stone conservation was ascertained in terms of thermostability and hydrophobicity by TG-DTA, DSC, dynamic mechanical analysis (DMA) and contact angle measurements.

Ethylenediamine-N,N'-disuccinic acid is a biodegradable alternative to EDTA, therefore its use for the sequestration of Ca(2+), Sn(2+), Cu(2+), Zn(2+) and Fe(3+) is analyzed. New data on its binding ability towards these cations were obtained with potentiometric, voltammetric and calorimetric measurements at different ionic strengths and at T = 298.15 K. Real multi-component fluids, namely fresh water, urine, sea water, saliva and blood plasma were chosen as case studies to evaluate the sequestering ability of EDDS in comparison with EDTA. Speciation diagrams were drawn in selected conditions, considering all interactions among the "natural" components of the fluid and those studied in this work, EDDS and EDTA (cL = 1 mmol dm(-3)) as sequestering agents and the cited metal cations (cM ∼ 10(-5) mol dm(-3)). The comparison of the sequestering ability of EDDS and EDTA is done using pM and pL0.5. In blood plasma the plasma mobilizing index was adopted. It was found that EDDS is a good alternative to EDTA, which tends to bind Ca(2+) and Mg(2+) more than EDDS. In particular, EDTA cannot be used as a sequestrant for Sn(2+) when cCa > cEDTA. EDDS is more efficient than EDTA at pH < 8, particularly in urine, where carbonate is absent. In sea water, the sequestering ability of EDDS towards Fe(3+) is higher than that of EDTA. In blood plasma, the PMI of EDDS towards Cu(2+) is higher than that of EDTA. Thermodynamic information, in terms of ΔH and ΔS, for the protonation and metal complex formation reactions are reported.

Protonation constants of 2-aminobenzoic acid, (anthranilic acid, vitamin L1) (1), 4-aminobenzoic acid (PABA) (2), and 2-aminoterephthalic acid (3) have been obtained from potentiometric measurements at 25 °C (298.15 K) and ionic strengths between 0 and 5 mol ⋅ dm − 3 NaCl and between 0 and 3 mol ⋅ dm − 3 (CH 3 ) 4 NCl. Values for the step-wise protonation constants log K 1 and log K 2 , extrapolated to zero ionic strength and infinite dilution, were determined as follows. For 2-aminobenzoic acid: 4.958 ± 0.003 (error estimate at the 95% confidence interval) and 2.060 ± 0.007; for 4-aminobenzoic acid: 4.868 ± 0.008 and 2.420 ± 0.004; for 2-aminoterephthalic acid: 5.089 ± 0.004 and 3.594 ± 0.006. Differences between protonation constants obtained using various concentrations of NaCl (aq) and (CH 3 ) 4 NCl (aq) for ionic strength adjustment are interpreted in terms of formation of weak complexes between the ligands and the ions of the background electrolyte. Values of log K for the formation of 1:1 complexes of the aminobenzoate anion with the tetramethylammonium cation have been estimated. The dependence of the solubility was studied as a function of NaCl (aq) and (CH 3 ) 4 NCl (aq) concentration. Similar behaviour was found for the three ligands. The total solubility increases with increasing NaCl (aq) concentration, whereas the opposite trend is observed in (CH 3 ) 4 NCl (aq) . Total and specific solubility was also determined, from which Setschenow coefficients and activity coefficients were deduced for the various species. Activity coefficient variation was examined in terms of both a Debye–Huckel type equation (DHt) and a SIT (Specific ion Interaction Theory) model.

In this paper, a study, at T = 298.15 K, on the thermodynamic properties and the complexing ability towards Zn 2 + of 2-mercaptopyridine-N-oxide (pyrithione, PT) and 2-hydroxypyridine-N-oxide (HPNO) is reported. For this purpose, different analytical techniques were used, potentiometry, voltammetry, atomic absorption and UV–visible spectroscopy. The equilibrium constants of the H + /HPNO and Zn 2 + /HPNO systems, together with the solubility of the Zn(HPNO) 2 species were determined in NaNO 3 aqueous solutions at different ionic strengths (0 I /mol·dm − 3 ≤ 3.2). For pyrithione, since reliable protonation constants have been recently published, the study was focused on its complexing ability towards Zn 2 + , and to the determination of the total and intrinsic solubility of the neutral Zn(PT) 2 species in NaCl at different ionic strengths (0 I /mol·dm − 3 ≤ 3.1). The speciation schemes of the two investigated Zn 2 + /L systems are similar, and consist of the ZnL + and ZnL 2 species. Generally, the formation constant values of the Zn 2 + /PT species are higher than those of the Zn 2 + /HPNO ones, for example, the stability of the ZnL + species is log K = 5.07 and 6.26 (at I = 0.1 mol·dm − 3 ) for HPNO and PT, respectively. At infinite dilution, the total solubility of the ZnL 2 species is: log S 0 T = − 4.291 ± 0.007 and − 1.241 ± 0.004 for the Zn(PT) 2 and Zn(HPNO) 2 , respectively. For these two species, the solubility product, K S0 , was also determined. The dependence on ionic strength of the equilibrium constants was modeled by the extended Debye–Huckel type equation (EDH) and the Specific ion Interaction Theory (SIT). Using this last model, the activity coefficients of all the species involved in the protonation and complex formation reactions were calculated. Furthermore, the formation of the mixed complex Zn(PT)(HPNO) was evidenced by means of spectrophotometric titrations, with a stability constant log β = 11.36 ± 0.06. In the case of pyrithione, the speciation study was performed also in a multicomponent solution simulating the composition of soaps.

In this paper, new data are reported on the protonation of phytate at T = 298.15 K in different ionic media and ionic strengths, namely NH4Cl(aq) (0.1 ⩽ I/mol · kg−1 ⩽ 1.9) and NaNO3(aq) (0.1 ⩽ I/mol · kg−1 ⩽ 5.4). A complete set of phytate protonation constants, with general formula HiPhy (with 1 ⩽ i ⩽ 7) was proposed. The data were modeled by a logarithmic empiric equation, as well as an Extended Debye–Huckel (EDH) and specific ion interaction theory (SIT) models. A strong similarity was found between protonation data in NH4Cl(aq), NaNO3(aq) and those previously reported in NaCl(aq), KCl(aq) and KNO3(aq), so that an unique set of thermodynamic protonation data has been proposed for phytate protonation at I ⩽ 0.15 mol · kg−1. Thermodynamic parameters obtained in these conditions can be useful to model the behavior of phytate in real aqueous systems at low ionic strengths. An empirical relationship has also been proposed for all the protonation data at 0 < I/mol · kg−1 ⩽ 0.15: TΔS (±1.5) = 11.7 − 0.72 · ΔG. Using literature data for the phytate protonation in (C2H5)4NI(aq), the weak complexes between Na+ or NH4+ and phytic acid have been calculated by the ΔpK method (i.e., by the comparison of the protonation constants determined in an interacting medium, such as NH4Cl(aq), and those obtained in a non-interacting supporting electrolytes, like tetraalkylammonium salts). In terms of weak complex formation constants, the results are similar for NaNO3(aq) and NH4Cl(aq), and twelve HiMjPhy species are reported together with their stability. For example, for the formation of the M6Phy species, it is: log β = 25.9 and 25.6 (±0.2) for M = Na+ and NH4+, respectively, at I = 0.1 mol · dm−3. This paper represents an advance in the understanding of the acid-base behavior of phytic acid in a wide number of ionic media at different ionic strengths.

Metal pollution, coming from both natural and anthropogenic sources, has become one of the most serious environmental problems. Various strategies have been tested with the aim of removing heavy metals from environment. In this contribution, containing a robust experimental work together with a critical literature analysis, the sequestering ability of a variety of ligands towards Sn2+ cation will be evaluated in the conditions of several natural fluids, i.e. sea water, fresh water, human blood plasma, urine and saliva. 13 structural and 11 thermodynamic descriptors will be selected for a total of thirty-eight molecules belonging to different classes (carboxylic acids, amines, amino acids, phosphonates, polyelectrolytes etc. …). For the filling of those missing data relative to the 11 thermodynamic descriptors, different strategies will be adopted, including simple correlations and Nipals algorithm. The evaluation of the sequestering ability of the ligands is assessed in terms of estimation of pL0.5 (total concentration of ligand required to bind the 50% of metal in solution), an empirical parameter that takes into account all the side reactions in solutions and does not depend on the speciation scheme. Partial least square calculations were performed to model the pL0.5 and to determine its correlation with the abovementioned descriptors. The possibility to design and build up new tailor-made molecules capable of effectively sequester Sn2+ in various conditions is crucial for practical applications in biosphere, hydrosphere and lithosphere.

A new type of coating, based on carboxylato-pillar[5]arene/poly(allylamine hydrochloride) multilayer films, for the sustained release of antibiotics with in vitro antiadhesive and antimicrobial activity against Gram-positive and Gram-negative bacteria is described.

The aim of the paper is to perform a critical analysis of the thermodynamic properties of five L-α-amino acids, namely arginine, aspartic acid, glutamic acid, glutamine and histidine. New potentiometric measurements to determine protonation constants and solubility (not for arginine) in NaCl and (CH3)4NCl aqueous solutions are reported, in order to investigate the medium effect. A preliminary analysis of the state of art evidenced the considerable amount of data in the ionic strength range 0 Finally, recommended, tentative or provisional data for protonation constants and protonation enthalpy changes of the five amino acids at different temperatures and ionic strengths are provided.

Landfill leachates can contaminate nearby aquifers. The hazards deriving from this contamination also depend on the chemical speciation of various contaminants. A novel approach is proposed here to face this problem from a chemical thermodynamics point of view. The complexing ability of the soluble fraction of a landfill leachate (collected from Bellolampo, Palermo, Italy) towards Pb2+, Cd2+ and Cu2+ has been investigated at T = 298.15 K in NaClaq at I = 0.1 mol dm−3. The soluble fraction of the landfill leachate was first characterized by different analytical techniques. Then, its acid–base properties were studied by ISE-H+ potentiometric titrations and modelled by the so-called diprotic-like model. Differential Pulse Anodic Stripping Voltammetry (DP-ASV) titrations of metal ion aqueous solutions with a diluted landfill leachate were carried out, successively, in order to determine the stability constants of the leachate-metal complexes. The stability of the Pb2+/OH− and Pb2+/Cl− complexes was also studied by the same technique. Finally, the sequestering ability of the leachate towards the investigated metal cations has been quantified by the calculations of various pL0.5 values under different pH conditions. The results proved that the landfill leachate is a good sequestering agent toward those cations, reducing the fraction of the free cations in solution, and that it can be a selective sequestrant at different pH.

This paper reports the results of a study on the interactions of tin(II) with different low molecular weight (poly)carboxylates (acetate (ac), malonate (mal), succinate (suc), adipate (adip), 1,2,3,-propanetricarboxylate (tca), 1,2,3,4-butanetetracarboxylate (btc), mellitate (mlt)), polyamines (putrescine (ptr), cadaverine (cdv), spermidine (spd), spermine (sper)), amino acids (glycinate (gly), aspartate (asp), glutamate (glu)), and S-donor ligands (thiolactate (tla), thiomalate (tma), penicilamine (pen)), at T = 298.15 K and I = 0.15 mol L− 1 in NaNO3(aq). Depending on the ligand, different MpLqHr species are formed (including the mixed ML(OH)), and the corresponding stability constants are reported. In the case of the Sn2 +-ac, Sn2 +-adip, Sn2 +-mlt and Sn2 +-asp systems, measurements at different ionic strengths (0.15 ≤ I/mol L− 1 ≤ 1.0) in NaNO3(aq) were also carried out, while experiments at different temperatures (298.15 ≤ T/K ≤ 313.15) have been performed only in the case of the Sn2 +-adip system, in order to evaluate and model the dependence of the stability of tin(II)/ligand species on these parameters. The sequestering ability of the investigated ligands toward tin(II) has been also evaluated by calculating various pL0.5 values (i.e., the total ligand concentration necessary to bind 50% of cation present in trace), a semiempirical parameter already proposed for the quantification of this ability in different conditions. Some empirical relationships are also presented, for a rough but immediate estimation of the stability of various tin(II)/ligand species as a function of the nature and number of the functional groups of different ligands.

Thermodynamic information about the metal-ligand interaction between Fe

The acid base properties of 1,2-dimethyl-3-hydroxypyridin-4-one (also known as deferiprone, def, figure 1 ), together with the solubility and the distribution ratio have been studied potentiometrically at different temperatures and ionic strengths in NaCl, KCl and in (CH3)4NCl aqueous solutions. The total solubility of deferiprone is fairly high (0.100 mol · dm−3 in pure water) and decreases with increasing salt concentration (salting out effect); this behaviour is greater in NaCl than in (CH3)4NCl aqueous solutions. From the analysis of the solubility and the distribution measurements it was possible to determine the Setschenow and the activity coefficients of the neutral species. Deferiprone shows two protonation steps, whose protonation constants are log K 1 H = 10.088 and log K 2 H = 3.656 at infinite dilution and T = 298.15 K. The ionic strength dependence of the protonation constants was interpreted both in terms of variation of the activity coefficients, using the Debye–Huckel, the SIT (Specific ion Interaction Theory) and the Pitzer approaches, or considering the formation of weak species with the ions of the supporting electrolyte (e.g. Na+, K+ and Cl−). Moreover, temperature gradients were provided for the two protonation constants. The stepwise protonation enthalpy values are negative in all cases (e.g. ΔH1 = −19.2 kJ · mol−1 and ΔH2 = −13.8 kJ · mol−1 at infinite dilution and T = 298.15 K) and become more negative increasing both temperature and ionic strength. It was observed that the proton binding process is mainly entropic in nature for the first protonation step and enthalpic for the second. The results are in good agreement with literature data.

Alkali metal ions play very important roles in all biological systems, some of them are essential for life. Their concentration depends on several physiological factors and is very variable. For example, sodium concentrations in human fluids vary from quite low (e.g., 8.2 mmol dm(-3) in mature maternal milk) to high values (0.14 mol dm(-3) in blood plasma). While many data on the concentration of Na(+) and K(+) in various fluids are available, the information on other alkali metal cations is scarce. Since many vital functions depend on the network of interactions occurring in various biofluids, this chapter reviews their complex formation with phosphates, nucleotides, amino acids, and related ligands of biological relevance. Literature data on this topic are quite rare if compared to other cations. Generally, the stability of alkali metal ion complexes of organic and inorganic ligands is rather low (usually log K 2) and depends on the charge of the ligand, owing to the ionic nature of the interactions. At the same time, the size of the cation is an important factor that influences the stability: very often, but not always (e.g., for sulfate), it follows the trend Li(+) Na(+) K(+) Rb(+) Cs(+). For example, for citrate it is: log K ML = 0.88, 0.80, 0.48, 0.38, and 0.13 at 25 °C and infinite dilution. Some considerations are made on the main aspects related to the difficulties in the determination of weak complexes. The importance of the alkali metal ion complexes was also studied in the light of modelling natural fluids and in the use of these cations as probes for different processes. Some empirical relationships are proposed for the dependence of the stability constants of Na(+) complexes on the ligand charge, as well as for correlations among log K values of NaL, KL or LiL species (L = generic ligand).

Alkali metal ions play very important roles in all biological systems, some of them are essential for life. Their concentration depends on several physiological factors and is very variable. For example, sodium concentrations in human fluids vary from quite low (e.g., 8.2 mmol dm−3 in mature maternal milk) to high values (0.14 mol dm−3 in blood plasma). While many data on the concentration of Na+ and K+ in various fluids are available, the information on other alkali metal cations is scarce. Since many vital functions depend on the network of interactions occurring in various biofluids, this chapter reviews their complex formation with phosphates, nucleotides, amino acids, and related ligands of biological relevance. Literature data on this topic are quite rare if compared to other cations. Generally, the stability of alkali metal ion complexes of organic and inorganic ligands is rather low (usually log K Na+ > K+ > Rb+ > Cs+. For example, for citrate it is: log KML = 0.88, 0.80, 0.48, 0.38, and 0.13 at 25 °C and infinite dilution. Some considerations are made on the main aspects related to the difficulties in the determination of weak complexes. The importance of the alkali metal ion complexes was also studied in the light of modelling natural fluids and in the use of these cations as probes for different processes. Some empirical relationships are proposed for the dependence of the stability constants of Na+ complexes on the ligand charge, as well as for correlations among log K values of NaL, KL or LiL species (L = generic ligand).

Polycationic oxacalix[4]arene 1·4HCl was found to be able to recognise, in water, the neutral π-rich aromatic guest 2,7-dihydroxynaphthalene, despite earlier studies indicating that the binding cleft of the oxacalixarene is π rich in nature. 1H NMR titrations at different pH values demonstrate that the tricationic receptor 1·3H+ displays the highest affinity towards DHN. According to a combination of NMR data and semiempirical (PM6) calculations, hydrophobic interactions play a prominent role in the formation of the complex.

In this paper, new information on physical and chemical properties of the widely used nanostructured Halloysite mineral are reported. Given that the Halloysite has a tubular structure formed by a variable number of wrapped layers containing Si-OH and Al-OH groups, their proton binding affinity was measured at different ionic strengths and ionic media by means of potentiometric measurements in heterogeneous phase. One protonation constant for the Si-OH groups and two for the Al-OH groups were determined. The protonation constant values increase with increasing of the ionic strength in all the ionic media. This suggests that the presence of a background electrolyte stabilizes the protonated species through the formation of weak complexes between ions of the supporting electrolytes and the protonated species. Ten weak species were determined with different stoichiometry. It was shown that the interactions do not depend on the nature of the supporting electrolytes but on the charge. The surface charge of Halloysite was estimated by ζ potential measurements as a function of pH, and the values obtained are consistent with the nanotubes ionization predicted by using the protonation constants for the Si-OH and Al-OH groups. The total solubility of the Halloysite nanotubes, was also determined in NaCl aqueous solution. These measurements showed that the solubility slightly increases with increasing ionic strength and contact time between Halloysite and NaCl solution. Goodness-of-fit (GOF) criteria were used to test the application of these models with good results. The obtained results confirm that the behavior of Halloysite in water is strictly correlated to the experimental conditions of the aqueous suspension (e.g., pH, ionic strength, and ionic media). The thermodynamic data here reported are of main importance in the several applications where is exploited the charge separation between the inner and outer surfaces of this nanotubular material.

In this paper, new potentiometric, calorimetric, and voltammetric measurements are reported to model the behavior of d-gluconic acid in aqueous NaCl(aq) and NaNO3(aq) ionic media at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15) also in the presence of Sn2+ and Zn2+. The protonation constants of d-gluconic acid (Gluc– in its deprotonated form) in NaCl(aq) and NaNO3(aq) are very similar. The dependence on ionic strength of the protonation constant was modeled by means of the extended Debye–Huckel type equation, the Specific ion Interaction Theory (SIT) and a weak interaction model. At infinite dilution and T = 298.15 K, the thermodynamic parameters for the proton binding reaction, determined by direct calorimetric titrations and temperature gradients of protonation constants, are log KH0 = 3.709 ± 0.004, ΔG0 = −21.18 ± 0.01 kJ mol–1, ΔH0 = −4.56 ± 0.04 kJ mol–1, and TΔS0 = 16.6 ± 0.1 kJ mol–1, indicating that the reaction is exothermic and entropic in nature. Potentiometric and voltamme...

The first water-soluble polycationic oxacalix[4]arene molecular tweezers able to recognize – under pH control – the paraquat dication as a result of a delicate balance between electrostatic repulsion, Coulombic shielding and attractive π-stacking interactions are reported.