Thermal decomposition of chemotherapeutic preparations and expectorants

The thermal decomposition of 31 drugs containing sulphonamides, antituberculous agents, dyes, an oxidant, carboxylic acid derivatives and formaldehyde, expectorants and codeine phosphate has been studied by differential thermal analysis (DTA) and thermogravimetry (TG). The DTA, TG and differential TG curves have been used for identification of the drugs and their qualitative and quantitative analysis. The results for 18 of the drugs were in good agreement with those calculated from the formulation.     

Thermal analysis of a model bio-membrane

Thermal properties of some shedded snake skins in comparison with human skins are represented by thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) to predict process condition as dermal pathway for administration of drugs or it be used as model membranes for permeation studies. Thermal behavior by TG/DTG and DTA curves for four kinds of shedded snake skins as Boelens Python (BP), Eastern Indigo Snake (EIS), Emerald Tree Boa (ETB), and Cascavel (CBR) were similar in relation to their decomposition temperatures at 100 °C and 230–400 °C of its constituents, however, their properties were different in the residue content (inorganic or carbonaceous substances). Similar thermal properties were also exhibited by human skins’ samples, however, they presented different residue and constituents’ content.     

Thermal degradation behaviour of some metal chelate polymer compounds with bis(bidentate) ligand by TG/DTG/DTA

Seven novel divalent transitional metal chelate polymers compounds (commonly known as chelate compounds or metal coordination complexes or polymer complexes) have been characterized by thermogravimetry (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA) methods. Thermal decomposition behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) polymers with terphthaoyl-bis(p-methoxyphenylcarbamide) has been investigated by thermogravimetric analysis (TGA) at heating rate 10 °C min^?1 under nitrogen atmosphere. TG/DTA of chelate compounds were shown to be a stable compound against thermal decomposition which was measured on the basis of final decomposing temperature, but it is observed in some curves that decomposition takes place at low temperature due to the lattice water, which is always placed at outer coordination sphere of the central metal ion. The presence of both lattice and coordinated water were noteworthy investigated in Co(II), Ni(II) and Cu(II) chelate polymer compounds, whereas lattice water found in Zn(II), Cd(II) and Hg(II). However, Mn(II) showed only coordinated water. Thermal stabilities for release of lattice water, coordinated water and organic moiety that occur in sequential decomposition of chelate compounds are explained on the basis of ionic size effect and electronegativity. The processes of thermal degradation taking place in seven chelate polymers were studied comparatively by TG/DTG/DTA curves which indicating the difference in the thermal decomposition. Coats–Redfern integral method is used to determine the kinetic parameters for the successive steps in the decomposition sequence of TG curves. Scanning electron microscope images of some chelate polymers were shown in previous publication revealed that particle sizes of chelate polymers were found to be of nanomaterial level therefore, resulting chelate compounds might be called as nanomaterial.     

Thermochemistry of some complexes of chromium(III) with imidazoles

The thermal decomposition in air of several complexes of chromium(III) with imidazole,N-methylimidazole and 2-methylimidazole has been studied with the aid of differential thermal analysis (DTA), thermogravimetry (TG) and derivative thermogravimetry (DTG) in the temperature range 25–600°C. Although the final process of the decomposition gives Cr₂O₃, there are interesting differences in the complete process of decomposition. The reasons for these differences appear to be related to the trans-effect and to the presence in the imidazole complexes of hydrogen bonds. Enthalpies of the several decomposition reactions have been determined by differential thermal analysis.     

Thermal stability and mechanical properties of sisal in cycle process

Differential thermal analysis (DTA) was the first thermal analysis technique used to qualitatively characterize natural clays and respective curves has been used since more than 60 years as their ‘fingerprint’. With the development of microprocessed equipments in the last decades, derivative thermogravimetric (DTG) curves also may be used for this purpose in some cases, which also may allow a quantitative characterization of clay components. TG and DTG curves are more indicated than DTA or DSC curves to identify and to better analyze the several decomposition steps of natural or synthetic organoclays. These questions are discussed in applications developed to characterize Brazilian kaolinitic clays, bentonites and organophilic clays.     

Studies on the thermal decomposition of salicylhydroxamic acid and its metal complexes with Ni(II), Co(II), Fe(II), Mn(II) and Zn(II)

The thermal decomposition of salicylhydroxamic acid and its metal complexes with Ni(II), Co(II), Fe(II), Mn(II) and Zn(II) has been studied by TG, DTG, DTA and IR spectroscopy. All the compounds investigated decompose to yield intermediate N-hydroxylactams.Decomposition schemes have been proposed and reaction enthalpies and kinetic parameters have been calculated.     

Thermal decomposition kinetics of diethyl dithiocarbamate complexes of copper(II) and nickel(II)

Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL₂ and NiL₂ (L^?=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL₂, DTG 250–350°, DTA 300–320° and for NiL₂, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

     

Thermal characterization of usnic acid/collagen-based films

The purpose of this study was to evaluate the physical–chemical properties of collagen (CL) and usnic acid/collagen-based (UAC) films, using differential thermal analysis (DTA), thermogravimetry (TG/DTG), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Both films were prepared by casting process using polyethylene glycol 1500 (PEG 1500) as plasticizer. In the spectrum of UAC, similar bands of the usnic acid are observed, indicating that the polymerization (film formation) did not affect the stability of the drug. Distinctly, DTA curve of UAC did not show an endothermic peak at 201 °C, indicative that the drug was incorporated into the polymeric system. These results were corroborated by the scanning electron microscopy (SEM). The TG/DTG curves of UAC presented a different thermal decomposition profile compared to the individual compounds and CL. These findings suggest the occurrence of molecular dispersion or solubilization of the drug in the collagen film.     

Thermal analysis of two series <Emphasis Type="Italic">mono</Emphasis>- and <Emphasis Type="Italic">di</Emphasis>-azocalix[4]arene derivatives

In the present study, thermal decomposition of mono- and di-azocalix[4]arene derivatives (A1–A8 and B1–B8) was investigated by means of thermogravimetry (TG), differential thermal analysis (DTA) and derivative thermogravimetry (DTG). The exclusion of methanol, hydrolysis of benzoyl ester and methyl ketone groups in lower rim, and decomposition of azo groups in upper rim have occurred during thermal analysis, consecutively. The thermal decomposition degrees amount of volatile pyrolysis products were determined in air atmosphere using TG, DTA and DTG curves. In conclusion, the thermal analyses of azocalix[4]arenes demonstrated that its stability depends on the substituted groups and their positions in the calix[4]arene structure.     

Thermal characterization of the poultry fat biodiesel

Chemical composition of oils and fats used in the biodiesel synthesis can influence in processing and storage conditions, due to the presence of unsaturated fatty acids. An important point is the study of the biodiesel thermal stability to evaluate its quality using thermal analysis methods. In this study the thermal stabilities of the poultry fat and of their ethyl (BEF) and methyl (BMF) biodiesels were determined with the use of thermogravimetry (TG/DTG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC), in different atmospheres. The TG/DTG curves of the poultry fat in synthetic air presented three decomposition steps while only one step was observed in nitrogen (N₂) atmosphere. The DSC results indicated four exothermic enthalpic transitions in synthetic air and an endothermic transitions in N₂ atmosphere attributed to the combustion process and to the volatilization and/or decomposition of the fatty acids, respectively. For both biodiesels the TG/DTG curves in air indicated two mass loss steps. In the DSC curves four exothermic transitions were observed in synthetic air besides an endothermic one in N₂ atmosphere.     

Thermal characteristics of novel NaH2PO4/NaHSO4 flame retardant system for polyurethane foams

The thermal decomposition of iminodiacetic, oxydiacetic, and thiodiacetic acids in helium atmosphere has been studied by means of thermogravimetry (TG), differential thermal analysis (DTA) and temperature-programmed pyrolysis directly coupled with mass spectrometry (TPPy-MS). Evolved gas analysis (EGA) profiles of iminodiacetic and oxydiacetic acids were obtained and compared with TG and DTA profiles. The decomposition of iminodiacetic acid forms water, CO, CO₂, CH₃CN, HCN and some hydrocarbons. After water evolution a cyclic anhydride is formed, as well as for oxydiacetic acid. Thiodiacetic acid vaporizes without decomposition.     

Selected thermoanalytical methods and their applications from medicine to construction

There are many thermoanalytical techniques but only several of them such as thermogravimetric analysis (TG), high resolution thermogravimetric analysis (Hi-Res™ TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), calorimetry, differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), evolved gas analysis (EGA), transient thermal analysis (TTA) and thermal conductivity (k) have selected to be discussed in this paper. Simultaneous thermal analysis (STA) is ideal for investigating issues such as the glass transition of modified glasses, binder burnout, dehydration of ceramic materials or decomposition behaviour of inorganic building materials, also with gas analysis. Selected applications of various thermoanalytical techniques from medicine to construction have also been discussed in this paper.     

Thermal decomposition of barium(II) tetraphenylborate

Barium(II) tetraphenylborate, Ba(Bph₄))₂·4H₂O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect.     

Thermal decomposition of ammonium copper chromate: effect of the addition of barium

The influence of the addition of barium (as barium chromate) to ammonium copper chromate on its thermal decomposition has been investigated by TG, DTG and DTA in the temperature range 303–1273 K. The solid products formed in the decomposition at different temperatures were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and also by measuring their specific surface area. The addition of BaCrO₄ at different concentrations (0–19.8%) was found not to change the general trend in the decomposition of ammonium copper chromate (which occurs in four distinct steps), except small changes in the temperature corresponding to DTG and DTA peaks. However, the sintering (or crystal growth) of the solid product is largely reduced by the presence of BaCrO₄.     

Thermal Studies of Di- and Triphenyltin(IV) Complexes of Salicylhydroxamic Acid

Thermal decomposition of di- and triphenyltin(IV) complexes derived from potassium salicylhydroxamate (KSHA) of compositions Ph2SnCl(SHA), Ph2Sn(SHA)2 and Ph3Sn(SHA) has been studied by TG, DTG and DTA. Based upon thermal mass losses the transitory formation of diphenyltin oxide, Ph2SnO as the possible intermediate from the decomposition pattern of all the three complexes has been proposed. Both DTG and DTA give well-defined peaks in the appropriate regions. These studies reveal the formation of SnO2 as the ultimate product. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of the thermal decomposition of commercial vegetable oils in air by simultaneous TG/DTA

This work presents a study of the thermal decomposition of commercial vegetable oils and of some of their thermal properties by termogravimetry (TG), derivative termogravimetry (DTG) and by differential thermal analysis (DTA). Canola, sunflower, corn, olive and soybean oils were studied. A simultaneous SDT 2960 TG/DTA from TA Instruments was used, with a heating rate of 10 K min^-1 from 30 to 700°C. A flow of 100 mL min^-1 of air as the purge gas was used in order to burnout the oils during analysis to estimate their heat of combustion. From the extrapolated decomposition onset temperatures obtained from TG curves, it can be seen that corn oil presents the highest thermal stability (306°C), followed by the sunflower one (304°C). Olive oil presents the lowest one (288°C). The heat of combustion of each oil was estimated from DTA curves, showing the highest value for the olive oil. Except for corn oil, which presents a significantly different thermal decomposition behavior than the other oils, a perfect linear correlation is observed, with negative slope, between the heat of combustion of an oil and its respective extrapolated onset temperature of decomposition in air. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition of cellulose hyphan and its complexes with rare earth elements and scandium

Thermal decomposition of cellulose hyphan (CH) and its complexes with Lu, Gd, Nd and Sc under an atmosphere of air has been studied using thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermal analysis (DTA). The results showed that, a different stages are accompanying the decomposition of (CH) and its complexes. These stages are affected by the presence of the metal ions. On the basis of the applicability of a non-isothermal kinetic equation, it was demonstrated that three main stages are involved in the decomposition processes. The activation energies of the different stages are calculated.

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Zusammenfassung Mittels TG, DTG und DTA wurde die thermische Zersetzung von Cellulosehyphan (CH) und seiner komplexe mit Lu, Gd, Nd und Sc an Luft untersucht. Es zeigte sich, da\ die Zersetzung von (CH) und seiner Komplexe von verschiedenen Schritten begleitet werden. Diese Schritte werden durch die Gegenwart der Metallionen beeinflu\t. Unter der Annahme der Anwendbarkeit einer nichtisothermen kinetischen Gleichung wurde gezeigt, da\ im Zersetzungsproze\ drei Hauptschritte inbegriffen sind. Die Aktivierungsenergie der verschiedenen Schritte wurde berechnet.

     

The Thermal Decomposition of Manganese Carbonate Thermogravimetry and Exoemission of Electrons

Results are reported on the thermal decomposition of manganese carbonate, MnCO₃. Thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermoanalysis (DTA) curves were recorded simultaneously and depicted together with the curve of intensity of electron exoemission (EEE). This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies on coordination compounds VI. Thermogravimetric,differential thermogravimetric,differential thermal analysis and mass spectrometric studies of some cobalt(II), nickel(II) and copper(II) salicylaldoximates, 2-indolecarboxylates and 2-thiophenecarboxylates

Some cobalt(II), nickel(II) and copper(II) complexes of salicylaldoxime, 2-indolecarboxylic and 2-thiophenecarboxylic acids were prepared and their thermal behaviour studied by TG, DTG, DTA and mass spectrometric methods. Kinetic parameters were calculated for the decomposition reactions if possible. The decomposition processes are discussed     

Characteristics of the thermal decomposition of antituberculous drugs

The thermal decomposition of antituberculous drugs-ethambutol (base and dihydrochloride), isoniazid, ethionamid and pyrazinamid has been studied by DTA, TG and DTG techniques. General remarks have been made on their thermal destruction. The effect of sample size over the range 20–200 mg and heating rate over the range 3–15 deg·min^?1 on the thermal degradation has also been investigated. Moreover, based on the Kissinger’s equation, the values of the kinetic parameters were determined.