The valorization of waste biomasses for recovering Critical Raw Materials (CRMs), particularly Rare Earth Elements (REEs), is a promising approach to enhance sustainability and resource efficiency. This study investigates the adsorption performance of bergamot, grape, and olive pomaces toward Nd3+ and Dy3+ ions under varying pH conditions, both in the absence of an ionic medium and in 0.10 mol/dm(3) NaNO3(aq), following different biomass pretreatment protocols. Comparative tests with La3+ enabled evaluation of light (Nd3+, La3+) vs. heavy (Dy3+) lanthanide ion behavior. Biomass characterization was performed using Attenuated Total Reflectance Fourier Transform Infrared (ATR FT-IR) spectroscopy and Scanning Electron Microscopy - Energy-Dispersive X-ray (SEM-EDX) analysis to assess changes in surface chemistry and morphology after adsorption. Kinetic and isotherm analyses showed pseudo-second-order kinetics and Langmuir behavior, respectively. The highest capacity was observed for water-pretreated bergamot pomace at 30 degrees C, pH 5.0, without ionic medium, and measured adsorption efficiency followed the trend: Dy3+ (0.45 mmol/g) > Nd3+ (0.38 mmol/g) > La3+ (0.35 mmol/g). The materials exhibited good reusability across adsorption/desorption cycles, supporting their potential as sustainable biosorbents. For the first time, direct isothermal titration calorimetry (ITC) was used to determine adsorption thermodynamics. Life Cycle Assessment (LCA) and Techno-Economic Assessment (TEA) further evaluated the environmental and economic feasibility of bergamot pomace under different processing scenarios.

(2S)-1-[(2S)-6-amino-2-[[(1S)-1-carboxy-3-phenylpropyl]amino]hexanoyl]pyrrolidine-2-carboxylic acid (Lisinopril) is a drug commonly used to treat hypertension and heart failure. In recent years, it has also been identified as an emerging environmental contaminant. In this study, the thermodynamic behavior of lisinopril in aqueous solution was investigated. The protonation constants of lisinopril were determined potentiometrically at different temperatures (288.15 <= T/K <= 310.15) and ionic strengths (0.16 <= I/mol kg-1(H2O) <= 0.97, NaCl). The findings indicate that the first two and the fourth protonation steps are driven by enthalpic contributions, whereas the third is slightly entropy driven. Furthermore, based on the distinct acid-base characteristics of the metal ions and the possible formation of sparingly soluble species, different speciation models were proposed for the various metal/lisinopril systems, including: ZnH2L+2, ZnHL+, CuHL+, CuL, CaL, CaHL+, MgL and MgHL+. The Specific Ion Interaction Theory (SIT) and a modified extended Debye-H & uuml;ckel equation were employed to model the thermodynamic formation parameters as a function of ionic strength and temperature. Finally, the distribution of lisinopril species (protonation and complex formation constants) under conditions simulating real systems, such as seawater, was evaluated.

The thermodynamics of 3-(diaminomethylidene)-1,1-dimethylguanidine (metformin) in aqueous solution were investigated. Metformin is a biguanide drug widely used in the treatment of type II diabetes mellitus. A systematic thermodynamic dataset over wide T and ionic strength ranges is currently lacking. Its acid–base properties and interactions with metal ions were studied by potentiometric titrations. The protonation constants of metformin were determined over a temperature range of 288.15 ≤ T/K ≤ 310.15 and an ionic strength range of 0.1 ≤ I/(mol kg−1 H2O) ≤ 1 (NaCl). The dependence of equilibrium constants on temperature and ionic strength was modeled using the van't Hoff equation, the Specific Ion Interaction Theory (SIT), and a modified extended Debye–Hückel equation. The best-fit speciation model included the species MgL, CuL, CuL22+, ZnLH3+, and ZnLOH+. Although the enthalpy changes associated with the two protonation steps are comparable, the first step shows a larger entropy contribution. These results provide a consistent thermodynamic framework for modelling metformin behaviour in biological and marine environments.

Trans-aconitic acid is a naturally occurring, biodegradable, unsaturated tricarboxylic acid that represents a promising sustainable alternative to conventional, poorly degradable chelating agents used in metal ion remediation. In this study, its acid-base behavior and chelating properties toward environmentally relevant divalent metal cations (Ca2+, Mg2+, Cu2+, Co2+, and Zn2+) were systematically investigated in an aqueous solution of potassium chloride (I = 0.10-1.00 mol dm-3) and at T = 298.15 K. A combined experimental and computational approach, including potentiometry, UV-vis and NMR spectroscopy, and Density Functional Theory (DFT) calculations, was employed to achieve a molecular-level thermodynamic characterization. The results indicate that trans-aconitic acid exhibits good sequestration efficiency, with a marked affinity toward Cu2+ and Mg2+ cations, as confirmed by pL0.5 and pM parameters as well as binding energy analyses. DFT calculations elucidated the microscopic acidities of the three carboxylic groups and rationalized the different interaction modes of Ca2+ and Mg2+. Overall, this study provides a comprehensive thermodynamic framework for trans-aconitic acid-metal interactions, supporting its potential application as an ecofriendly ligand for metal ion remediation and scale prevention in natural and industrial waters.

Despite its widespread use in pharmaceuticals, cosmetics, and animal nutrition, the environmental implications of nicotinamide remain largely underexplored. Given its high solubility and prevalent presence in wastewaters, nicotinamide has been proposed as a potential environmental marker and emerging contaminant. This study focuses on the evaluation and modeling of medium and ionic strength effects on the acid-base behavior of nicotinamide in aqueous solution. To this aim, the protonation constants of nicotinamide were determined in aqueous media containing various supporting electrolytes (sodium chloride, tetramethylammonium chloride, tetraethylammonium iodide) at T = 298.15 K and different ionic strengths. The medium and ionic strength dependencies were described through well-established thermodynamic models, including the Extended Debye-H & uuml;ckel equation, the Specific ion Interaction Theory, and the Pitzer approach. Additionally, the Setschenow constant of nicotinamide was determined through distribution measurements between 1-octanol and NaCl(aq) solutions. Furthermore, a critical data analysis was performed to assess the reliability of the proposed models and provided interaction parameters. Overall, this work thoroughly describes the acid-base behavior of nicotinamide in different aqueous media and its distribution between aqueous and organic phases, offering fundamental insights for the assessment of its chemical speciation in real systems, which is crucial for future applications in environmental monitoring and remediation strategies.

Tranexamic acid (TXA) is the main component of antihemorrhagic drugs but is also used as an ingredient in cosmetic formulations for its depigmenting action. The acid-base properties were investigated in aqueous solutions containing NaCl, KCl, and (CH3)4NCl, at different ionic strengths, at T = 298.15 ± 0.15 K and only in NaCl(aq) at 283.15 ≤ T/K ≤ 318.15. The different behavior of TXA in the diverse media was explained by the formation of weak complexes with the components of the ionic media. The complexing ability of TXA toward Ca2+, Mg2+, Zn2+, and Sn2+, at T = 298.15 ± 0.15 K, was studied in NaCl(aq) in the range of 0.15 ≤ I/mol dm-3 ≤ 1.0; the modeling of the formation constants with ionic strength was performed by an extended Debye-Hückel type equation and the Specific ion Interaction Theory. For all M2+/TXA systems, the common M-(TXA) species was obtained, and in the same experimental conditions, the stability trend observed is logK SnTXA > logK ZnTXA > logK MgTXA > logK CaTXA . The sequestering ability of TXA toward the metals was estimated by means of pL0.5. To complete the picture of the chemical behavior of TXA, some simulations in blood plasma were also performed.

This study presents a detailed thermodynamic investigation on the protonation behavior of tartronic acid in aqueous solutions of various ionic media, including sodium chloride, potassium chloride, tetramethylammonium chloride, and tetraethylammonium iodide. Specifically, potentiometric measurements were performed at temperatures ranging from 288.15 to 310.15 K and ionic strengths between 0.1 and 1.0 mol dm−3 to determine stoichiometric protonation constants in different ionic media. The formation of weak complexes between tartronate and alkaline metal cations was obtained by means of the ΔpK method. Moreover, data were modeled using the Debye–Hückel equation and Specific Ion Interaction Theory (SIT), allowing for the calculation of standard thermodynamic parameters and the assessment of the dependence of protonation constants on ionic strength. Additionally, the protonation behavior of tartronic acid was compared with that of structurally related acids, such as malonic and mesoxalic acids, providing insights into the role of molecular structure in acid dissociation. The results emphasize the significant role of entropic contributions in the protonation process and provide a comprehensive model for the thermodynamic properties of tartronic acid across a wide range of experimental conditions.

The thermodynamics of the interaction between (S)-(+)-3-aminomethyl-5-methylhexanoic acid (pregabalin) and protons was studied potentiometrically at different temperatures (288.15 <= T/K <= 310.15), ionic strengths (0.16 <= I/mol kg(-1)(H2O) <= 0.97, NaCl), (0.11 <= I/mol kg(-1)(H2O) <= 1.11, (C2H5)(4)NI), (0.10 <= I/mol kg(-1)(H2O) <= 1.03, NaClO4, only at T = 298.15 K). The protonation constants at infinite dilution and the corresponding enthalpy change values were determined, as well as their parameters for the dependence on the temperature and ionic strength. The results showed that the protonation reactions are exothermic, and that the entropic contribution is the driving force of the processes. Formation constants of pregabalin (L) with Zn2+, Cu2+, Ca2+, and Mg2+ were determined in NaCl(aq) at different ionic strength values, at 298.15 K. Different speciation models were proposed for the various metal/Pregabalin systems: ZnHL2+, ZnLOH(aq)0, CuL+, CuL2(aq)0, CaL+, CaHL2+, and MgL+, depending on the different acid-base properties of the metals and the possible formation of sparingly soluble species. The modelling of the thermodynamic formation parameters respect to the temperature and ionic strength variation was carried out by using both the Specific Ion Interaction Theory (SIT) and an extended Debye-H & uuml;ckel type equation. Being Pregabalin an emerging contaminant, it was interesting to investigate its distribution in presence of the investigated metal cations in aqueous solution simulating both biological fluid (urine) and natural water (seawater).

The interactions of Fe3+ with some ligands (Tranexamic (TXA−), Indole-3-acetic (IAA−), and Aminomethylphosphonic (AMPA2−) acids) of biological and environmental interest were studied. The speciation studies were performed in NaNO3(aq) and NaCl(aq) using potentiometric and, only for IAA−, spectrophotometric titrations at T = 298.15 K and 0.01 ≤ I/mol dm−3 ≤ 1.0. The proposed speciation models are as follows: Fe(TXA)H3+, Fe(TXA)2+, Fe(TXA)(OH)+, and Fe(TXA)(OH)2(aq) for TXA−; Fe(IAA)2+ for IAA−; and Fe(AMPA)H23+, Fe(AMPA)H2+, and Fe(AMPA)+ for AMPA2−. A comparison of logβ for the common FeL species gives logβFeIAA = 6.56 and logβFeAMPA = 14.84 (at I = 1.00 mol dm−3 and T = 298.15 K), suggesting that AMPA2− has a higher complexing ability towards Fe3+ than IAA−. The dependence on the ionic strength of the formation constants was modeled by means of a Debye–Hückel type equation and the SIT model, whilst the sequestering ability of the investigated ligands towards Fe3+ was quantified at various pHs, ionic strengths, and in the different supporting electrolytes by means of an empirical pL0.5 parameter. To complete this study of the behavior of the different Fe3+/ligand systems, various simulations in biological fluids and natural waters were conducted.

Carbon Quantum Dots (CQDs) are versatile nanomaterials known for their tuneable optical properties and strong photoluminescence, making them suitable for potential use in various environmental and sensing applications. In this study, CQDs were synthesized via hydrothermal treatment of bergamot pomace, a citrus industry byproduct, in line with green chemistry and circular economy principles. A full factorial experimental design was employed to systematically optimize the quantum yield (Phi) by varying reaction time, temperature, and precursor concentration. The best model included positive linear parameters, interaction terms involving temperature and time, as well as the quadratic parameter for the precursor concentration. The quadratic parameters relative to time were found to be negative and indicated an optimised reaction time at similar to 9 h. The resulting CQDs were extensively characterized. UV-Vis absorption and fluorescence spectroscopy showed the typical CQD optical features with minor variations depending on the synthesis conditions. Raman spectroscopy revealed characteristic D and G bands and allowed for an estimation of the particle diameters (<= 62.28 nm), while TEM measurements showed particle size up to 52.5 nm, with higher uniformity for lower reaction temperatures. DLS suggests the nanoparticle aggregation in aqueous solution, supported by HPLC which also revealed two distinct CQDs families. ATR-FTIR and potentiometric titrations indicate predominance of carboxylate groups on the product surface. Overall, this study presents a structured optimization strategy for enhancing CQD properties from renewable feedstocks and highlights their potential for future integration into environmental monitoring systems.

Ethylenediaminetetraacetic acid (EDTA) is, so far, the most known and widely used chelating agent. It is well known to form very stable mononuclear complexes with several metal ions in aqueous solution. However, its multidentate nature opens the possibility to simultaneously bind more than one cation forming polynuclear species, rarely observed for EDTA, but common for its analogues like, e.g., DTPA and TTHA. If formed, these species could significantly affect the speciation of both EDTA and metal ions in solution. As such, in this work we report the result of a potentiometric investigation on the chemical speciation of three model systems, namely: Sn2+/Zn2+/EDTA, Sn2+/Fe2+/EDTA and Zn2+/Fe3+/EDTA, at T = 298.15 K and I = 0.15 mol⋅dm‒3 (in NaNO3(aq) or NaClO4(aq)), as a proof of concept that simple and mixed polynuclear species can be also formed by EDTA. In fact, experimental data analysis evidenced the formation of not only the simple Sn2(EDTA), Zn2(EDTA) and [Fe2(EDTA)]2+ species, but also the mixed SnZn(EDTA), SnFe(EDTA) and [ZnFe(EDTA)]+. The formation of latter species was then analyzed in terms of thermodynamic extra stability with respect to simple species, and their influence on the speciation of EDTA and the investigated cations was evaluated. Furthermore, quantum mechanical calculations were also performed for a better insight on the binding mode of EDTA when forming dinuclear species, and to support the evidence concerning the extra stability of mixed ones. We could conclude that, when forming dinuclear species, EDTA behaves as a tridentate ligand, binding cations through two carboxylates and one amino group (MIDA-like mode).

In this work, the coordination properties of 8-hydroxyquinoline-2-carboxylic acid (8-HQA, LH2) toward Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ are discussed. Stability constants for Mn2+, Co2+, and Ni2+/8-HQA systems were determined by ISE-H+ (glass electrode) potentiometry, and those of Cu2+ and Zn2+/8-HQA by ultraviolet-visible (UV-vis) spectrophotometry, in KCl(aq) at I = 0.2 mol dm-3 and T = 298.2 K. For all systems, three species are formed: MLH+, ML, and ML2 2-. 8-HQA proved a good sequestering agent of M2+ over a wide pH range, as also shown by the calculated pL0.5 values. The stability of the formed metal complexes follows the expected Irving-Williams trend, especially concerning the ML2 2- species, with log β120: 12.45 ± 0.01 (Mn2+) < 13.45 (Fe2+) < 15.90 ± 0.04 (Co2+) < 17.17 ± 0.05 (Ni2+) < 20.64 ± 0.03 (Cu2+) > 18.78 ± 0.02 (Zn2+). This trend is inversely correlated to the M-N bond length determined by quantum mechanical calculations. These studies, together with voltammetry and electron paramagnetic resonance spectroscopy, allowed us to derive information about the coordination modes, structure, and nature of the formed species. Results support the formation of ML2 2- complexes over possible ML-(OH)-, with 8-HQA acting as tridentate in all formed species, including the protonated MLH+.

The definition of reliable equilibrium constants is an essential step in speciation studies, as the uncertainty and the consistency of the estimated values concur to define the reliability of the speciation model. It is therefore necessary to evaluate the uncertainty contribution of all factors involved at each step of the data acquisition procedure and to be aware about the consequences of systematic errors on the best-estimated values of experimentally measured equilibrium constants. In this work, a series of computer-generated H+-ion selective electrode titration curves simulating the alkalimetric titration of equimolar mixtures of Zn2+-EDTA in aqueous solutions have been processed by different equilibrium data fitting software. Hence, the uncertainties of the refined stability constants of the Zn2+-EDTA complexes could be derived, while excluding the experimental variability that intrinsically affects all practical experiments. The sensitivity of a given chemical system to different data processing strategies and to possible errors in the input data was evaluated. The systematic errors considered relate to the potential reading, the concentration of the titrant and solution components, and ionic strength variations during titrations. The outcomes highlight how unsuitable decisions taken at the stage of nonlinear least squares fitting of the data can affect the results and underline that the main error contribution is related to the measurement of the glass-electrode potential. The processing of simulated data sets can be a useful tool to alert the researchers to the sensitivity of a given chemical system to different strategies and to possible errors in the input data.

The identification of archaeological biomarkers is one of the main objectives of analytical chemistry in the archaeological field. However, no information is currently available on biomarkers able to unambiguously indicate the presence of olive oil, a cornerstone of Mediterranean ancient societies lifestyle, in an organic residue. This study aims to bridge this gap by a thorough characterization of the degradation products of extra-virgin olive oils (EVOOs) resulting from in-lab thermal oxidative treatments, with the primary goal of revealing potential archaeological biomarkers for olive oil. Thirty-three EVOOs sourced from eleven different monocultivars across five Italian regions (Sicily, Apulia, Lazio, Tuscany, and Liguria) and Spain, were analyzed before and after thermal oxidation. In addition, an identical thermal treatment was employed on pure triglyceride standards (triolein, trilinolein, and tristearin), due to the high concentration of their fatty acids in EVOO discerning their degradation patterns. A combination of analytical strategies was employed, including HPLC-MS and HPLC-ELSD for the complete evaluation of the intact lipids (triglycerides, diglycerides, and their oxidative species) in olive oils before and after oxidation, and HS-SPME-GC-MS and GC-FID for the characterization of secondary oxidation products formed by the thermal treatment. In addition, to elucidate the fatty acid distribution in the oxidized EVOOs by GC-MS and GC-FID techniques a derivatization step was performed to convert lipid compounds into trimethylsilyl (TMS) derivatives. A chemometric approach was used to thoroughly interpret the data obtained from intact and oxidized samples. This comprehensive investigation sheds light on the chemical transformations of EVOOs under thermal oxidative conditions and indicates mono-carboxylic acids such as pentanoic, hexanoic, heptanoic, octanoic, nonanoic, and decanoic acids as potential archaeological biomarkers for the presence of lipid substances coming from olive oil in archaeological organic residues. Finally, lipid contents from twenty-four real archaeological samples, grouped in amphorae (10), unguentaria (5), and lamps (9), excavated from the Roman domus of Villa San Pancrazio in Taormina (Italy), were determined. The analytical results obtained from amphorae samples revealed the presence of the selected olive oil-specific archaeological biomarkers, an information extremely interesting considering that this type of amphorae have so far been solely associated with the storage of wine.

A multi-analytical approach was used to comprehensively characterize the acid-base, thermal, and surface properties of agri-food processing wastes (i.e., original and pre-treated bergamot, grape and olive pomaces). These biomasses, often underutilised and inadequately studied in terms of their physicochemical properties, were investigated under varying ionic strength conditions at t = 25 °C. This investigation uniquely integrates multiple advanced techniques: Brunauer–Emmett–Teller porosimetry, Scanning Electron Microscopy, Thermogravimetric Analysis coupled with Fourier Transform Infrared Spectroscopy, Differential Scanning Calorimetry, Attenuated Total Reflectance Fourier-Transform Infrared, and potentiometry to provide a holistic understanding of these biomasses potential for environmental remediation. The modelling of ionic strength-dependent acid-base behaviour, established using an extended Debye–Hückel-type equation, revealed the dominant role of carboxylic groups as active sites across all pomace types, although with variations in abundances across the different samples. Additionally, morphological analysis highlighted the presence of irregularly shaped particles, heterogeneous size distributions, and distinct thermal stability trends, with grape pomace exhibiting the highest mass loss. These findings underscore the significant potential of these biomasses for the remediation of cationic pollutants from natural waters. Moreover, this comprehensive characterisation not only advances the understanding of agri-food waste valorisation but also provides a robust framework for designing targeted strategies in environmental applications.

Organometal cations are dangerous pollutants of natural waters, causing severe environmental and biological problems. In contrast, gallic acid (GA) is a naturally occurring polyphenol found in citrus fruit peels, honey, grapes, hops, oak bark, and tea leaves, displaying several beneficial properties. Performing a contaminant speciation study in conditions simulating the ones characteristic of real environmental matrices, is essential for gaining information on the pollutant mobility, transport, toxicity, environmental impact and fate. In this light, an investigation on the GA stability and acid-base properties, as well as, for the first time, on the ligand interactions with two organometal cations, namely methylmercury(II) (CH3Hg+) and dimethyltin(IV) ((CH3)2Sn2+), was carried out by means of potentiometry, UV-VIS spectrophotometry, 1H NMR spectroscopy and spectrofluorimetry. The thermodynamic data showed for gallic acid higher complexation and sequestering abilities towards dimethyltin(IV) with respect to methylmercury(II), demonstrating the ligand promising and selective performances as potential decontaminating agent for the (CH3)2Sn2+ remediation from polluted sites. This study could also contribute to the development of environmental strategies aimed at the production of new gallic-acid based sustainable materials dealing with the organometal contamination issue, as well as for potential applications in various industrial fields.

In this investigation, Gantrez™ AN-169 (anhydride of the monoalkyl esters of poly(methyl vinyl ether/maleic acid); GTZ4−, L″) copolymer, widely employed in different industrial and application fields, was tested as sequestering agent of the two cited components.The speciation of Eph− in the presence of GTZ4− and Cu2+ was studied at the temperature of T = 298.15 K, and at the ionic strength value of I = 0.15 mol dm−3 in NaCl(aq). The formation of binary and ternary complexes was investigated, and the possible Eph−/GTZ4− interaction was analyzed by ISE-[H+] potentiometry and DOSY NMR. The dependence of the equilibrium constants on I/mol dm−3 and T/K was studied using an extended Debye-Hückel and a Van’t Hoff equation, allowing the modelling of the thermodynamic parameters (i.e., equilibrium constants and enthalpy change values of formation). The entropic contribution was found to be the driving force behind the complex formation. The sequestering ability of Eph− and GTZ4− on Cu2+, evaluated by the pL0.5 calculation, increases with pH and ionic strength.Since freshwater and seawater are generally the final destination of wastewaters, simulations were carried out in aqueous solutions simulating these two natural media, with the aim of highlighting which are the main species of the components under those conditions.

Deferiprone, generally, is considered an important chelating agent for Fe3+ overload. From a literature data analysis, a lack of information on the interaction of this molecule toward a series of metal cations emerged, inducing to fill out the topic. The complexing ability of deferiprone toward Ca2+, Mg2+, Cd2+ and Pb2+ was studied by potentiometry and 1H NMR spectroscopy, in KCl aqueous solutions at different ionic strength values (0.1 ≤ I/mol dm−3 ≤ 1.0) and T = 298.15 K. The same speciation model featured by the ML, ML2, ML3 and ML(OH) (M = metal and L = deferiprone or DFP) species was obtained for Cd2+ and Pb2+; the formation constants calculated at infinite dilution are: logTβ = 7.23±0.02, 12.47±0.03, 16.70±0.04, and −2.53±0.04, respectively for Cd2+ and 9.91±0.01, 15.99±0.02, 19.93±0.05 and 0.99±0.02 for Pb2+. Only two species, namely ML and ML2, were determined for Ca2+ and Mg2+, whose formation constants at infinite dilution are respectively: 3.72±0.01 and 6.50±0.02, for the first one, 5.31±0.01 and 9.58±0.01, for the second. The ligand sequestering ability and affinity toward M2+ were evaluated by determining the pL0.5 and pM parameters at different pHs and ionic strengths. The results suggest that deferiprone has the best complexing and sequestering ability toward Pb2+, followed by Cd2+, Mg2+ and Ca2+, respectively. 1H NMR studies confirmed the DFP affinity for Cd2+ and Pb2+, and in combination with DFT calculations showed that metal cations are bound to the hydroxo-oxo moiety of the pyridinone ring. The data reported in this study provide information on the possible employment of a small molecule like deferiprone, as a chelating and sequestering agent for Pb2+ accumulation or overload from environmental and biological matrices.

The thermodynamics of interaction of trans-aconitate (L3-) with proton, sodium and potassium cations was studied by means of potentiometric titration performed at different temperatures, ionic strengths, and aqueous ionic media (NaCl, KCl and (C2H5)4NI). Three protonation constants and corresponding enthalpy changes are reported at infinite dilution together with their dependence parameters on temperature and ionic strength according to van't Hoff and Extended Debye Huckel equations, respectively. Enthalpy changes resulted slightly endothermic at infinite dilution and values decrease with increasing ionic strength. Proton binding resulted always entropic in nature. Weak association constants of Na+/L3-and K+/L3-species were determined using the pure water model approach. Formation constants of trans-aconitate with Cd2+, Pb2+ and Mn2+ were determined in KCl(aq) at different ionic strength values and at 298.15 K. Three complex species were found with all metal cations (ML-, MHL0(aq), MH2L+), whose formation constant values at infinite dilution and at T = 298.15 K were log & beta; = 4.54, 9.94, 13.77 for cadmium, 5.00, 10.57, 14.81 for manganese and 4.97, 10.44, 14.13 for lead. The as found values resulted unexpectedly high. The sequestering ability of trans-aconitate towards M2+ was evaluated by determining pL0.5 (the ligand total concentration required to bind 50% of the metal cation), and the results show that, throughout the investigated pH range, trans-aconitate shows the highest sequestering ability towards Mn2+. Data reported in this paper were critically compared to other tricarboxylic acid, namely citric and tricarballylic acid.

The thermodynamics of interaction of a second-generation bisphosphonate drug, 4-amino-1-hydroxy-1-phosphonobutyl phosphonic acid mono sodium (sodium alendronate) with H+, Ca2+ and Mg2+ has been investigated. The protonation constants were determined in NaCl and (C2H5)(4)NI aqueous solutions at different ionic strengths (0.10 <= I/mol kg(-1)(H2O) <= 1.02) and temperatures (288.15 <= T/K <= 310.15) by using the ISE-[H+] potentiometry. The differences of the log K-i(H) in the two ionic media were interpreted in terms of activity coefficient variations and formation of Na+ weak complexes. The interactions with Mg2+ and Ca2+ were studied in NaCl(aq) (0.10 <= I/ mol kg(-1) (H2O) <= 1.02) and T = 298.15 K. Two different speciation models were obtained; Ca2+: CaH2L, CaHL, CaL. Mg2+: MgH3L, MgH2L, MgHL, MgL. The dependence of the thermodynamic parameters on the ionic strength and temperature was modelled by means of the Specific Ion Interaction Theory (SIT) and a modified Debye-Huckel equation including a term for the dependence on T/K. The first two protonation equilibria are exothermic, and the reactions are not favoured by an increase of the temperature whilst the last two are endothermic. The entropic contribution resulted to be the driving force of the reactions. The sequestering ability of alendronate towards the two metal cations was quantified by means of the pL(0.5) parameter calculated at different pHs and ionic strengths. It resulted that alendronate has a higher sequestration toward Mg2+ with respect to Ca2+. A simulation of the alendronate behaviour in human blood plasma was carried out