Carlo Maccà - Academia.edu (original) (raw)

Papers by Carlo Maccà

Chemischer Informationsdienst, Jun 11, 1974

Analytica Chimica Acta, 1983

A new method for the determination of the selectivity coefficient of an ion selective electrode i... more A new method for the determination of the selectivity coefficient of an ion selective electrode is proposed. In the proposed method, a series of mixed solutions of the primary ion i and interfering ion j is prepared in which the sum of the logarithm of i concentration and logarithm of j concentration is kept constant. The potential of the electrode, E, is measured for the series of the mixed solutions. The result is plotted with the activity of i, a;, as abscissa against E on semi-logarithmic graph paper. The activity at the intersection of two extrapolated linear parts of the log a;-E curve is determined. From the activity at the intersection of the primary ion, the selectivity coefficient is calculated. The proposed method was applied to the determination of selectivity coefficients of fluoride, chloride, bromide and potassium selective electrodes. The selectivity coefficients determined by the proposed method, named 'continuous variation method'', agreed with those obtained with the conventional mixed solution method.

Journal of electroanalytical chemistry and interfacial electrochemistry, Feb 1, 1974

In recent years, several authors a investigated the formation of complex species in the so called... more In recent years, several authors a investigated the formation of complex species in the so called "hydrous" melts, i.e. extremely concentrated solutions of salts in water. According to the quasi-lattice model developed by Braunstein z for this kind of melt, the value of the equilibrium constant K1 for the formation of the complex MX from M + and X-(present as low concentration solutes in a saltwater mixture) is related to the composition of the solvent by the equation

Journal of electroanalytical chemistry, Apr 10, 1974

Chemischer Informationsdienst, Feb 14, 1978

ChemInform Abstract Das Löslichkeitsgleichgewicht AgzO in LiNO3+KNO3-Schmelzen (30-59 mol-% LiNO3... more ChemInform Abstract Das Löslichkeitsgleichgewicht AgzO in LiNO3+KNO3-Schmelzen (30-59 mol-% LiNO3) in Gegenwart von H2O bei bekannter Aktivität wird mit Hilfe von EMK-Messungen an einer galvanischen Kette des Typs A im Temp.-Bereich 415 bis 525 K ntersucht. Die Abhängigkeit der Löslichkeit von der Zusammensetzung des Lösungsmittelgemisches wird modellmässig interpretiert.

Analyst, 1990

The application of Gran plots to potentiometric complexation titrations of mixtures of two metals... more The application of Gran plots to potentiometric complexation titrations of mixtures of two metals with a selective electrode for one of the metal ions is surveyed. New developments are discussed; only 1:1 reactions are considered. Depending on the ratio between the conditional stability constants of the two metal chelates, the first and/or second equivalence point can be found by using different forms of approximately linear Gran functions. Criteria for identifying the linear range of Gran functions using logarithmic diagrams are illustrated. Rigorous equations for linearised titrations are introduced.

Journal of the Chemical Society, 1976

A statistical thermodynamic treatment of ion-molecule association processes in ionic melts has be... more A statistical thermodynamic treatment of ion-molecule association processes in ionic melts has been developed on the basis of the quasi-lattice model, under the hypothesis that the neutral molecules bccupy “interstitial” sites in the quasi-lattice of the melt.With the assumption that the number of such sites available around each cation is approximately equal to the cation–anion coordination number, the resulting equations for the configurational association entropies fit satisfactorily the existing experimental data, without the need to resort to any other out-of-model hypothesis.

Chemical communications, 1966

Journal of Chemical Education, Dec 1, 1983

Although in recent years the theoretical shape of potentiometric titration curves has been the su... more Although in recent years the theoretical shape of potentiometric titration curves has been the subject of a thorough discussion (!), in the common use, and especially in the teaching practice, some ambiguities still persist, even on important features.

Talanta, Apr 30, 2007

The pH-stat titration technique is an autonomous and very powerful tool for performing and monito... more The pH-stat titration technique is an autonomous and very powerful tool for performing and monitoring chelatometric titrations of metal cations with great accuracy, poorly known, however, and seldom exploited. Based on measurement of the amount of strong base required to keep the pH of the test solution at a selected value during stepwise known additions of ethylenedinitrilotetraacetate (EDTA), it requires a glass electrode as the only sensor and is easily implemented on potentiometric titrators. It was introduced a quarter of century ago on an empirical basis for a very peculiar purpose (determination of calcium in diary products), but only very recently it was generalised and its fundamentals were thoroughly examined. In this work, pH-static titrations of some transition metal cations of analytical relevance (Co 2+ , Cu 2+ , Mn 2+ , Zn 2+) were thoroughly investigated in the acid pH range between 2.3 and 5 or 7 (the highest pH depending on the metal hydroxide or carbonate solubility). The results at higher acidity showed unsuspected properties of such chelation reactions. At moderately acid pH (generally ≥4), indeed, pH-static titrations yield results of high precision and accuracy. On decreasing pH, however, the reaction stoichiomety deviates more and more from the 1:1 ratio between chelating agent and cation, seemingly because of formation of binuclear complexes, an occurrence very seldom mentioned in the current literature. The optimal titration conditions for each metal are defined, and directions for establishing a laboratory protocol for quantitative determinations are given.

Talanta, Apr 15, 2007

The alkaline-luminol/H 2 O 2-based chemiluminescent (CL) detection of Fe 2+ , Co 2+ , and Mn 2+ ,... more The alkaline-luminol/H 2 O 2-based chemiluminescent (CL) detection of Fe 2+ , Co 2+ , and Mn 2+ , separated with a Dionex CS5A ion chromatographic phase was studied by means of a multi-pump flow system allowing the variation of the post-column solution composition. A perchlorate gradient at pH 1.9 (with HCl) was used to separate cations partially complexed with 5.6 mM oxalate present in the eluent and necessary for the chosen separation phase. A 0.91 mM luminol, 3.3 mM H 2 O 2 in 0.25 M carbonate buffer at pH 10.5 composition was chosen as CL reagent solution. The chosen pH value warrants signal repeatability and wider linearity range although absolute signal is not maximum. The CL signal was related to the pH of the two post-column mixing solutions. Calibration plots of Co 2+ and Fe 2+ were linear in the chosen concentration range whilst a parabolic model was the best fit for Mn 2+. Detection limits were 0.24, 0.50 and 375 nM for Co 2+ , Fe 2+ and Mn 2+ , respectively. The method was used to determine Co 2+ at trace level in commercial copper chelates used for animal feeding. A comparison with a chromatographic method with spectrophotometric detection was made giving results comparable both in absolute values and accuracy.

Journal of electroanalytical chemistry and interfacial electrochemistry, Apr 1, 1972

* When the solvent was lithium nitrate or a lithium-containing mixture, sodium chromate or potass... more * When the solvent was lithium nitrate or a lithium-containing mixture, sodium chromate or potassium chromate was added, lithium chromate not being available. The effect on the solvent composition and on the measured association energy can be considered negligible, as generally the total alkali chromate added was not more than 1 o~ of the alkali nitrate.

Journal of electroanalytical chemistry and interfacial electrochemistry, May 1, 1972

Talanta, Dec 1, 1994

Potentiometric characterization of weak acids by multiple sample addition II. The effect of chemi... more Potentiometric characterization of weak acids by multiple sample addition II. The effect of chemical interferences and the practical performance of linearization methods

Journal of Medicinal Chemistry, Feb 8, 2006

Gold(III) compounds are emerging as a new class of metal complexes with outstanding cytotoxic pro... more Gold(III) compounds are emerging as a new class of metal complexes with outstanding cytotoxic properties and are presently being evaluated as potential antitumor agents. We report here on the solution and electrochemical properties, and the biological behavior of some gold(III) dithiocarbamate derivatives which have been recently proved to be one to 4 orders of magnitude more cytotoxic in vitro than the reference drug (cisplatin) and to be able to overcome to a large extent both intrinsic and acquired resistance to cisplatin itself. Their solution properties have been monitored in order to study their stability under physiological conditions; remarkably, they have shown to undergo complete hydrolysis within 1 h, the metal center remaining in the +3 oxidation state. Their DNA binding properties and ability in hemolyzing red blood cells have been also evaluated. These gold(III) complexes show high reactivity toward some biologically important isolated macromolecules, resulting in a dramatic inhibition of both DNA and RNA synthesis and inducing DNA lesions with a faster kinetics than cisplatin. Nevertheless, they also induce a strong and fast hemolytic effect (compared to cisplatin), suggesting that intracellular DNA might not represent their primary or exclusive biological target.

Electroanalysis, 2002

The pH-static option available in many potentiometric titrators can be exploited for acid-base ti... more The pH-static option available in many potentiometric titrators can be exploited for acid-base titrations. The procedure consists of continuous or stepwise addition of the titrand solution to a suitable supporting solution (containing an inert electrolyte and, if necessary, a small concentration of buffer), and simultaneous addition of titrant to keep the measured pH at an appropriate constant value. Titrations of moderately concentrated strong and weak acids and bases are theoretically investigated. The criteria of choice of the experimental parameters, particularly of operating pH, ionic strength and buffer power of the measured solution, are discussed. The way these parameters affect the accuracy and the precision of the results is examined. It is inferred that pH-static titrations can be competitive with traditional titration procedures, particularly for the determination of the effective strength of secondary standard solutions of strong bases. Moreover, they can be used straightforwardly for the determination of acidity constants.

Journal of Chemical Education, Feb 1, 1986

Talanta, Jul 1, 1996

Acid-base equilibria in aqueous solutions of cis-bis(trimethylphosphine)platinum(II) dinitrate at... more Acid-base equilibria in aqueous solutions of cis-bis(trimethylphosphine)platinum(II) dinitrate at 25 °C, 0.2 M ionic strength (KNO3), have been investigated by potentiometry with a glass electrode. The procedure consisted of multiple addition of the investigated analyte to a supporting electrolyte solution (“multiple sample addition”) and subsequent titration with strong base. For the treatment of potentiometric multiple sample addition data, a new

Analytical and Bioanalytical Chemistry, 1987

Journal of Chemical Education, Aug 1, 1986