U.Biader Ceipidor

Complexes of divalent metal ions with cinchomeronic and dinicotinic acid thermal properties

Abstract The thermal properties of the complexes of cinchomeronic and dinicotinic acid with several divalent metal ions were determined by thermogravimetry (TG) and differential thermal analysis (DTA). For the thermal stability of the anhydrous compounds a sequence may be observed for the metal ions with cinchomeronic (3,4-H 2 PC) and dinicotinic acid (3,5-H 2 PC): The thermal stability of the pyridine carboxylic acid for each metal of the series is: dinicotinic > cinchomeronic The activation energy values for each thermal reaction were also calculated, using the Coats and Redfern algorism, by the Univac 1108 computer, by a program properly implemented for the statistical analysis of the data to obtain the reaction order and the activation parameters with the relative confidence limits.

Thermal analysis of some chromium(III) complexes with dicarboxylic ligands

Abstract The solid chromium(III) complexes with a series of dicarboxylic ligands were prepared as potassium salts and examined by TG, DTG and DSC. The results are discussed in terms of basicity by arranging the ligands in proper series.

Using thermoanalytical data. Part 2. The dependence of kinetic data available from thermogravimetry on sample and instrument parameters: a method for calculating ‘true’ kinetic parameters

Abstract Kinetic data available from TG measurements are discussed with respect to thermal coefficients such as sample specific heat, reaction enthalpy, instrument heat-transfer coefficient and heat capacity. The dependence of the available kinetic parameters Z, E and N on these thermal coefficients is examined using a numerical model. A relationship is also derived for calculating the kinetic parameters from experimental TG curves whilst taking into account the perturbation induced by the above-cited thermal coefficients. The dehydration of calcium oxalate is used to evaluate experimentally the predictive power of the kinetic parameters obtained in this way, i.e. their ability to describe the sample behaviour under a wide range of operational conditions (different masses and heating rates), including isothermal reactions.

Cholic acids determination from heats of fusion obtained using differential scanning calorimetry. Application to pharmaceutical products

Abstract The possibility of quantitatively analyzing some cholic acids by DSC is proposed using the heats of fusion. Some characteristic parameters of these analytical techniques have been evaluated for cholic, deoxycholic, chenodeoxycholic, ursodeoxycholic and lithocholic acids. The method has been applied to the analysis of two commercial drugs containing chenodeoxycholic and ursodeoxycholic acid, respectively. The results obtained are fully discussed.

Analytical comparison of calorimetric, enzymatic and chemical methods for the quantitative determination of cholic acids

Abstract Several methods for the determination of cholic acids have been examined using pure cholic acid as standard. Some analytical aspects have been checked and evaluated. Two methods based on DSC were considered using the detection and measurement of the heats of oxidation and heats of fusion, respectively. The results were compared with those obtained both by the enzymatic method using 3α-hydroxysteroid dehydrogenase as reagent and by a chemical method based on the Pettenkofer reaction. Operative procedures of the last method have been tested and improved with respect to the Irvin procedure in some cases. The discussion is reported in terms of precision, sensitivity and possible fields of application for the examined method.

Using thermoanalytical data: Part 4. Processing of DTA/DSC curves to calculate reaction enthalpy and kinetic parameters. An application to calcium oxalate

Abstract With regard to single step reactions, a new approach to the processing of DTA/DSC curves is presented, taking into account the heat transfer into the instrument. It is an extension of a previous physical model, that allowed the calculation of true kinetic parameters from TG curves. The peak area can be properly calculated as well as the degree of reaction, this also being suitable for kinetic parameters calculation. Through numerical simulations, other methods for DTA/DSC curve processing are discussed with respect to that proposed. By TG and DTA, the true kinetic parameters have been finally determined for the second and third steps of the thermal decomposition of CaC 2 0 4 sdH 2 O, to complete previously reported data for the first dehydration step. The agreement of the results with isothermal experiments seems to indicate a way to escape from the dichotomy between isothermal and non-isothermal kinetics. Several other approaches to non isothermal kinetics are reviewed and discussed. The software developed is also briefly described.

Application of thermal analytical methods to pharmaceutical products. Cephalosporins

Abstract A series of sodium salts of antibiotics belonging to the cephalosporin group has been analyzed by such thermoanalytical techniques as TG, DTG and DSC. No melting processes have been identified. The heating process, mainly carried out in a stream of oxygen, shows thermal reactions starting at about 150°C. Sodium sulphate was found as residue at temperatures around 600–650°C. From the residue, which has a well-defined composition, it is possible to dose the sodium to a higher degree of accuracy than that obtained by flame photometry. In addition, the analytical time required for pretreatment of the sample is shorter.

Using thermoanalytical data: Part 3. Influence of calorimetric and instrumental parameters on estimating kinetic parameters by TG

Abstract The influence of calorimetric parameters on estimation of kinetic parameters by TG is considered. A numerical model is used to highlight the correlation displayed by the parameters themselves and the possibility of representing kinetic parameters as a linear combination of variables, describing heat transfer contributions, is examined. Simulations, using the previously determined kinetic parameters for calcium oxalate dehydration, show the limitations of such an approach, even though interesting observations are derived. The previously reported iterative method for kinetic parameters calculation therefore should not be replaced by a general linear combination.

Solvent effects on the formation equilibria of cobalt(II)-chloride system in acetone-water mixture

The data about cobalt(II) - chloride complexes in acetone solution have been completed by recent spectrophotometric methods (K3=4.5 107; K4=6.1 102). Furthermore, the influence of water addition on the system has been pointed out by considering the dielectric and donor properties of the solvent mixture. The results show a linear correlation of the complex species distribution with the reciprocal dielectric constant of the simple binary system, so that a possible explanation of the present data and of those of some oher authors has been discussed in terms of DEC influence on dissociation reactions. Donor number equality for water and acetone has made it possible to minimize the solvent influence on the ionization processes when varying water-acetone ratio.

SeSaMoNet: an RFID-based economically viable navigation system for the visually impaired

In this article, the authors present secure and safe mobility network (SeSaMoNet), a navigation and environment description system for users with visual impairments. The system is designed with attention to usability and accessibility features and for its great scalability. The spread of mobile technology such as handheld devices and related software, personal digital assistants and smartphones, wireless communication, text-to-speech, databases and finally radio frequency identification made it possible for the authors to build a portable, easy to use orientation and navigation aid that still has a great development margin. A double version, Symbian and Windows Mobile, allows quite every type of user equipment to be supported. The system aims to provide a non-intrusive and accessible way to expand the experiences of people with visual impairments and provide them with useful information about the environment beyond the tactile probing of the closest surroundings. This article expands previous work, detail...