The solubility and acid–base properties of the antibacterial Ofloxacin were studied in aqueous solutions of sodium chloride at a single ionic strength value (
I
= 0.15 mol·dm
−3
) and different ...temperatures. Hydronation constants were investigated at
T
= 288.15, 298.15, 310.15 and 318.15 K by potentiometric and UV-spectrophotometric titrations. From the distribution of the different hydronated/dehydronated Ofloxacin species, it was observed that at physiological pH, the neutral HL
0
(zwitterion) species has a mole fraction percentage of ~ 85%. A lowering trend of the hydronation constants with increasing
T
/K was observed and the standard enthalpy, entropy and the Gibbs energy of hydronation were also calculated. The solubility (
S
T
), investigated at
T
= 288.15, 295.15, 310.15 K, was determined by UV-spectrophotometric measurements by using the calibration straight line method. Absorbance values of the standard Ofloxacin solutions and of the saturated solutions were measured at two wavelengths (
λ
= 287 nm and 331.5 nm), and the concentration of Ofloxacin was calculated from the slope of the straight lines. The concentration of Ofloxacin neutral species (
S
0
) was calculated from simple mass balance equations, by using the free hydrogen ion concentration of the saturated solutions and hydronation constants determined at the same ionic strength and temperature of the solubility measurements. From the experimental results, it was possible to observe a different effect of the temperature on solubility and hydronation constants. In the first case, the solubility increases almost linearly with the increase of the temperature, while the hydronation constants decrease by about 0.2 logarithmic units passing from
T
= 288.15 to 318.15 K. By using a Van’t Hoff equation as modified by Apelblat, the standard enthalpy, entropy and the Gibbs energy of solution were calculated by the slope and the intercept of the straight lines obtained by fitting ln
x
against 1/
T
, where
x
is the solubility of Ofloxacin expressed as mole fraction. By using an approach reported in the literature, calculated hydronation constants were obtained at different ionic strengths (up to 1.0 mol⋅dm
−3
) and at the same temperatures experimentally investigated. Successively, by means of a Debye–Hückel type equation, the corresponding hydronation constants at infinite dilution and the parameters for the dependence on the ionic strength were calculated, as well as the enthalpy change values of hydronation at infinite dilution. A very good agreement was obtained from the comparison of the hydronation constants and solubility of Ofloxacin here determined and those reported in pure water in the literature.
Several studies have been performed so far for the effective recovery, detection and quantification of specific compounds and their degradation products in archaeological materials. According to the ...literature, lipid molecules are the most durable and widespread biomarkers in ancient pottery. Artificial ageing studies to simulate lipid alterations over time have been reported. In this review, specific lipid archaeological biomarkers and well-established sampling and extraction methodologies are discussed. Although suitable analytical techniques have unraveled archaeological questions, some issues remain open such as the need to introduce innovative and miniaturized protocols to avoid extractions with organic solvents, which are often laborious and non-environmentally friendly.
Hydroxypyridinones (HPs) are recognized as excellent chemical tools for engineering a diversity of metal chelating agents, with high affinity for
metal ions, exhibiting a broad range of activities ...and applications, namely in medical, biological and environmental contexts. They are easily made and functionalizable towards the tuning of their pharmacokinetic properties or the improving of their metal complex thermodynamic stabilities. In this review, an analysis of the recently published works on hydroxypyridinone-based ligands, that have been mostly addressed for environmental applications, namely for remediation of
metal ion ecotoxicity in living beings and other biological matrices is carried out. In particular, herein the most recent developments in the design of new chelating systems, from bidentate mono-HP to polydentate multi-HP derivatives, with a structural diversity of soluble or solid-supported backbones are outlined. Along with the ligand design, an analysis of the relationship between their structures and activities is presented and discussed, namely associated with the metal affinity and the thermodynamic stability of the corresponding metal complexes.
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.
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•Speciation study on the deferiprone interactions toward Ca2+, Mg2+, Cd2+, Pb2+.•Potential use of deferiprone ligand to remove Pb2+ contamination.•Future applications on real environmental matrixes.
The binding ability of five bifunctional 3-hydroxy-4-pyridinones towards Cu
and Fe
was studied by means of potentiometric and UV-Vis spectrophotometric measurements carried out at
= 0.15 mol L
in ...NaCl
= 298.15 K and 310.15 K. The data treatments allowed us to determine speciation schemes featured by metal-ligand species with different stoichiometry and stability, owing to the various functional groups present in the 3-hydroxy-4-pyridinones structures, which could potentially participate in the metal complexation, and in the Cu
and Fe
behaviour in aqueous solution. Furthermore, the sequestering ability and metal chelating affinity of the ligands were investigated by the determination of p
and pM parameters at different pH conditions. Finally, a comparison between the Cu
and Fe
/3-hydroxy-4-pyridinones data herein presented with those already reported in the literature on the interaction of Zn
and Al
with the same ligands showed that, from the thermodynamic point of view, the 3-hydroxy-4-pyridinones are particularly selective towards Fe
and could therefore be considered promising iron-chelating agents, also avoiding the possibility of competition, and eventually the depletion, of essential metal cations of biological and environmental relevance, such as Cu
and Zn
.
The interactions of epinephrine ((
)-(-)-3,4-dihydroxy-α-(methylaminomethyl)benzyl alcohol;
) with different toxic cations (methylmercury(II): CH
Hg
; dimethyltin(IV): (CH
)
Sn
; dioxouranium(VI): UO
...) were studied in NaCl
at different ionic strengths and at
= 298.15 K (
= 310.15 K for (CH
)
Sn
). The enthalpy changes for the protonation of epinephrine and its complex formation with UO
were also determined using isoperibolic titration calorimetry:
= -39 ± 1 kJ mol
,
= -67 ± 1 kJ mol
(overall reaction),
= -26 ± 4 kJ mol
, and
= 39 ± 2 kJ mol
. The results were that UO
complexation by
was an entropy-driven process. The dependence on the ionic strength of protonation and the complex formation constants was modeled using the extended Debye-Hückel, specific ion interaction theory (SIT), and Pitzer approaches. The sequestering ability of adrenaline toward the investigated cations was evaluated using the calculation of pL
parameters. The sequestering ability trend resulted in the following: UO
>> (CH
)
Sn
> CH
Hg
. For example, at
= 0.15 mol dm
and pH = 7.4 (pH = 9.5 for CH
Hg
), pL
= 7.68, 5.64, and 2.40 for UO
, (CH
)
Sn
, and CH
Hg
, respectively. Here, the pH is with respect to ionic strength in terms of sequestration.
The thermodynamics of the interaction of L-glutamic-N,N-diacetic acid (GLDA) with protons was studied potentiometrically at different temperatures, ionic strengths and ionic media. Four protonation ...constants and corresponding enthalpy changes occurred at infinite dilution together with temperature and ionic strength coefficients. The medium effect was also interpreted in terms of the formation of weak complexes between the ligand and the cations of supporting electrolytes, resulting in a greater tendency of GLDA to chemically interact with Na+ rather than K+ and, in turn, (CH3)4N+. Formation constants of GLDA with Cd2+ were determined in NaCl(aq) at different ionic strength values. Five complex species were found, namely CdL2−, CdHL−, CdH2L0(aq), Cd2L0(aq), and Cd(OH)L3−, whose formation constant values at infinite dilution were log β = 12.68, 17.61, 20.76, 17.52, and 1.77, respectively. All the species results were relevant in the pH range of natural waters, although the Cd2L0(aq) was observed only for CCd ≥ CGLDA and concentrations of >0.1 mmol dm−3. The sequestering ability of GLDA toward Cd2+, evaluated by means of pL0.5, was maximum at pH~10, whereas the presence of a chloride containing a supporting electrolyte exerted a negative effect. Among new generation biodegradable ligands, GLDA was the most efficient in Cd2+ sequestration.
The interactions of dopamine 2-(3,4-Dihydroxyphenyl)ethylamine, (Dop−) with cadmium(II), copper(II) and uranyl(VI) were studied in NaCl(aq) at different ionic strengths (0 ≤ I/mol dm−3 ≤ 1.0) and ...temperatures (288.15 ≤ T/K ≤ 318.15). From the elaboration of the experimental data, it was found that the speciation models are featured by species of different stoichiometry and stability. In particular for cadmium, the formation of only MLH, ML and ML2 (M = Cd2+; L = dopamine) species was obtained. For uranyl(VI) (UO22+), the speciation scheme is influenced by the use of UO2(acetate)2 salt as a chemical; in this case, the formation of ML2, MLOH and the ternary MLAc (Ac = acetate) species in a wide pH range was observed. The most complex speciation model was obtained for the interaction of Cu2+ with dopamine; in this case we observed the formation of the following species: ML2, M2L, M2L2, M2L2(OH)2, M2LOH and ML2OH. These speciation models were determined at each ionic strength and temperature investigated. As a further contribution to this kind of investigation, the ternary interactions of dopamine with UO22+/Cd2+ and UO22+/Cu2+ were investigated at I = 0.15 mol dm−3 and T = 298.15K. These systems have different speciation models, with the MM’L and M2M’L2OH M = UO22+; M’ = Cd2+ or Cu2+, L = dopamine common species; the species of the mixed Cd2+ containing system have a higher stability with respect the Cu2+ containing one. The dependence on the ionic strength of complex formation constants was modelled by using both an extended Debye–Hückel equation that included the Van’t Hoff term for the calculation of the formation enthalpy change values and the Specific Ion Interaction Theory (SIT). The results highlighted that, in general, the entropy is the driving force of the process. The quantification of the effective sequestering ability of dopamine towards the studied cations was evaluated by using a Boltzmann-type equation and the calculation of pL0.5 parameter. The sequestering ability was quantified at different ionic strengths, temperatures and pHs, and this resulted, in general, that the pL0.5 trend was always: UO22+ > Cu2+ > Cd2+.
The speciation of epinephrine (
) in the presence of alginate (
) and two biological and environmental relevant metal cations (Cu
, UO
) was investigated at
= 298.15K,
= 0.15-1.00 mol dm
in NaCl
. ...The formation of binary and ternary complexes was evaluated and, since epinephrine can behave as a zwitterion, the
/
interaction was studied by means of DOSY NMR. The dependence of the equilibrium constants on ionic strength was studied using an extended Debye-Hückel type equation and the SIT approach. The effect of temperature was investigated by means of isoperibolic titration calorimetry: the entropic contribution was the driving force for the Cu
/
complexes formation. The sequestering ability of
and
on Cu
, evaluated by the pL
calculation, increased with pH and ionic strength. The determination of pM parameter showed that
had a higher Cu
affinity with respect to
. The formation of
/
species was also investigated by UV-Vis spectrophotometry and
H NMR measurements. The ternary Cu
/
/
and Cu
/UO
/
interactions were also studied. The "extra-stability" calculated for the mixed ternary species confirmed that their formation was thermodynamically favorable.
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).
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