The single salt approximation for the major components of seawater: association and acid–base properties

In this note we propose the use of the single salt approximation for the composition of seawater. This approximation has been applied to a synthetic seawater. Association and acid-base properties h..

Chemical speciation of nucleotide 5′-monophosphates in the presence of biogenic amines

The interaction of adenosine-, uridine-, inosine- and guanosine-5'-monophosphates with protonated ethylenediamine, putrescine, cadaverine, spermidine and spermine, was studied potentiometrically, a..

Sequestration of Alkyltin(IV) Compounds in Aqueous Solution: Formation, Stability, and Empirical Relationships for the Binding of Dimethyltin(IV) Cation by N- and O-Donor Ligands

The sequestering ability of polyamines and aminoacids of biological and environmental relevance (namely, ethylenediamine, putrescine, spermine, a polyallylamine, a branched polyethyleneimine, aspartate, glycinate, lysinate) toward dimethyltin(IV) cation was evaluated. The stability of various dimethyltin(IV) / ligand species was determined in NaClaq at t = 25°C and at different ionic strengths (0.1 ≤ I/mol L−1 ≤ 1.0), and the dependence of stability constants on this parameter was modeled by an Extended Debye-Hückel equation and by Specific ion Interaction Theory (SIT) approach. At I = 0.1 mol L−1, for the ML species we have log K = 10.8, 14.2, 12.0, 14.7, 11.9, 7.7, 13.7, and 8.0 for ethylenediamine, putrescine, polyallylamine, spermine, polyethyleneimine, glycinate, lysinate, and aspartate, respectively. The sequestering ability toward dimethyltin(IV) cation was defined by calculating the parameter pL50 (the total ligand concentration, as −log CL, able to bind 50% of metal cation), able to give an objective representation of this ability. Equations were formulated to model the dependence of pL50 on different variables, such as ionic strength and pH, and other empirical predictive relationships were also found

speciation of chitosan with low and high molecular weight carboxylates in aqueous solution

Quantitative data on the speciation of chitosan (310kDa) with low and high molecular weight carboxylates in aqueous solution are reported. The following carboxylic ligands were considered: monocarboxylate (butyrate); dicarboxylates (malonate, succinate, azelate); tricarboxylate (1,2,3-propanetricarboxylate); tetracarboxylate (1,2,3,4-butanetetracarboxylate); polyacrylates (2.0 and 20kDa); polymethacrylate (5.4kDa). The investigation was performed by potentiometry at t ¼ 25 � C, at low ionic strength (without addition of supporting electrolyte) and at I ¼ 0:15mol L � 1 (NaCl). For all the systems the formation of (chitosan)LHi species was found (L ¼carboxylic ligand; i ¼1 to 4 depending on the carboxylic ligand considered). The stability of proton–chitosan–carboxylate species depends on the number of carboxylic groups involved in the complexation, and it was possible to calculate a rough free energy value per bond DGn ¼� 15 � 2kJ mol � 1 . By using the stability data, the quantitative sequestering capacity of chitosan towards the carboxylates here considered [expressed as the–log(total chitosan concentration) necessary to bind 50% of carboxylate, i.e., pL50] was calculated for different pH values, at low ionic strength and at I ¼ 0:15mol L � 1 . The pL50 values, ranging from 3 to 7, show that chitosan is quite a strong sequestering agent towards carboxylates. Evidences were also obtained for the different behaviour between low and high molecular weight carboxylates

speciation of poly amino carboxylic compounds in seawater

AbstractIn this work quantitative data on the interaction of EDTA and EGTA with the major inorganic components of seawater are reported. Protonation constants and alkali and alkaline earth metal complex formation constants are reported at different ionic strengths (0< l/mol L−1≤1). These formation data were obtained from potentiometric measurements in several single and mixed electrolyte media (such as artificial seawater). Potentiometric measurements in artificial seawater (containing Na+, K+, Mg2+, Ca2+, Cl−and SO42−) were analysed by using the single salt approximation (the artificial seawater being considered as a single salt BA whose ions have fractional charge -zanion = zcation = 1.117). Several species BpHrL (L = EDTA or EGTA) are formed and their formation constants are reported at different salinities. Present results, together with similar data on the complexing capability of NTA, DTPA and TTHA towards inorganic components of natural fluids, allowed to find general conclusions on the important c..

sequestration of organometallic compounds by synthetic and naturally occurring polycarboxylate ligands binding of monomethylmercury ii by polyacrylic and alginic acids

AbstractThe sequestering capacity of synthetic and naturally occurring polycarboxylate ligands towards mono-methylmercury(II) was evaluated by stability quantitative data on the interaction of CH3Hg+ with different molecular weight synthetic polyacrylates (2 and 20kDa average M.wt) and alginate (70–100 kDa) extracted from brown algae Macrocystis pyrifera. The influence of ionic medium was evaluated by measurements on the CH3Hg+-polyacrylate systems in NaNO3 medium at different ionic strengths (0.10, 0.25, 0.50 and 0.75 mol L−1), and a Debye-HiJckel type equation was used for the dependence of complex formation constants on ionic strength. Measurements on the CH3Hg+ - alginate system were carried out at l = 0.10 mol L−1 in NaNO3 medium. By using the stability data, the sequestering capacity of both ligands towards monomethylmercury(II) was determined at different pH values. Results obtained show that the binding ability of polyacrylic ligands (PAA) is stronger than the alginate (AA), following the trend PA..

Thermodynamic Behavior of Polyalcohols and Speciation Studies in the Presence of Divalent Metal Cations

The acid–base properties and complexing ability of some biologically relevant polyalcohols (erythritol, sorbitol, maltol, and ethylmaltol) toward bivalent metal cations have been determined by pote..

Speciation Studies of Bifunctional 3-Hydroxy-4-Pyridinone Ligands in the Presence of Zn2+ at Different Ionic Strengths and Temperatures

The acid-base properties of two bifunctional 3-hydroxy-4-pyridinone ligands and their chelating capacity towards Zn2+, an essential bio-metal cation, were investigated in NaCl aqueous solutions by potentiometric, UV-Vis spectrophotometric, and 1H NMR spectroscopic titrations, carried out at 0.15 ≤ I/mol -1 ≤ 1.00 and 288.15 ≤ T/K ≤ 310.15. A study at I = 0.15 mol L-1 and T = 298.15 K was also performed for other three Zn2+/Lz- systems, with ligands belonging to the same family of compounds. The processing of experimental data allowed the determination of protonation and stability constants, which showed accordance with the data obtained from the different analytical techniques used, and with those reported in the literature for the same class of compounds. ESI-MS spectrometric measurements provided support for the formation of the different Zn2+/ligand species, while computational molecular simulations allowed information to be gained on the metal-ligand coordination. The dependence on ionic strength and the temperature of equilibrium constants were investigated by means of the extended Debye-Hückel model, the classical specific ion interaction theory, and the van't Hoff equations, respectively