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Abstract  

The potential of hyphenating thermogravimetry (TG) and soft photo ionisation mass spectrometry (EBEL-SPI-MS) for fundamental and applied research and material analysis has been demonstrated by a newly developed TG-SPI quadrupole MS coupling (TG-SPI-QMS). Thermal decomposition of three common plastics, polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC) has been studied. While the decomposition of PE and PS in inert atmosphere takes place in a one step process (main mass loss at about 490 and 420 °C, respectively), PVC decomposes in a two step mechanism. The organic signature of the PE decomposition shows homologous series of alkenes and polyenes, while PS is forming mainly styrene mono- and oligomers. In the PVC decomposition, firstly hydrogen chloride (HCl) is eliminated in a hydro-dechlorination reaction (1st mass loss step: 285–305 °C), this is accompanied by the emission of the carbon skeletons of small aromatics (predominately benzene and naphthalene). In the second step (2nd mass loss step: 490–510 °C), the residual cross-linked polyolefin moieties decompose under release of heavily alkylated aromatics, including larger PAH. Chlorinated aromatics are formed only in trace levels.

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Abstract  

A new formulation of nifedipine tablets was prepared. The tablets were conditioned in amber-colored glass containers and placed in a climatized room at 40 °C and relative humidity of 75% for 180 days. Differential scanning calorimetry (DSC) and Thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two well-known nifedipine degradation products. There is no evidence of interaction between nifedipine and excipients or degradation products. High performance liquid chromatography (HPLC) was used in the dosage of nifedipine tablets before and after acclimatized exposure. Results show that DSC and TG offer important data for a more detailed assessment of the stability of a pharmaceutical formulation.

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Journal of Thermal Analysis and Calorimetry
Authors: Lakshmi Kaza, Hany F. Sobhi, Jeffrey A. Fruscella, Chris Kaul, Shravan Thakur, Naullage I. Perera, Kenneth Alexander, and Alan T. Riga

Abstract

A standard protocol was developed to determine the water content by thermal analysis of milk of magnesia (MoM). Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in a novel manner for examining the physical characteristics of the commercial pharmaceutical suspensions. Moisture analyzer and oven-dry methods validate the proposed protocol. MoM consists primarily of water and magnesium hydroxide [Mg(OH)2]. Experimental design of the thermal analysis parameters were considered including sample size, flowing atmosphere, sample pan, and heating rate for both DSC and TG. The results established the optimum conditions for minimizing heat and mass transfer effect. Sample sizes used were: (5–15 mg) for DSC and (30–50 mg) for TG. DSC analysis used crimped crucibles with a pinhole, which allowed maximum resolution and gave well-defined mass (water) loss. TG analysis used a heating rate of 10 °C/min−1 in an atmosphere of nitrogen. The heat of crystallization, heat of fusion, and heat of vaporization of unbound water are 334, 334, and 2,257 Jg−1, respectively (Mitra et al. Proc NATAS Annu Conf Therm Anal Appl 30:203–208, ). The DSC average water content of (MoM) was 80 wt% for name brand and 89.5 wt% for generic brand, based on the relative crystallization, melting and vaporization heats/Jg−1 of distilled water in the recently purchased (2011) MoM samples. The TG showed a two-step process, losing water at 80–135 °C for unbound water and bound water (MgO·H2O) at 376–404 °C, yielding a total average water loss of 91.9 % for name brand and 90.7 % for generic brand by mass. The difference between the high-temperature TG and the lower-temperature DSC can be attributed for the decomposition of magnesium hydroxide or MgO·H2O. Therefore in performing this new approach to water analysis by heating to a high temperature decomposed the magnesium hydroxide residue. It was determined that the TG method was the most accurate for determining bound and unbound water.

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Abstract  

A series of different commercial membranes were characterized by their moisture absorption and desorption properties under controlled humidity and temperature conditions. This work was made possible by combining the features of a constant humidity conditioning chamber with those of a thermogravimetric (TG) apparatus. These two modules were interconnected by tubing, rotameters, an atmosphere-recycling microbellows pump and switching valves. Under programmed heating and isothermal conditions reproducible data were obtained in terms of weight-gain or weight-lossvs. time and pore size. Evaluation of the resulting TG curves allowed us to report reasonable differences in the materials, some of which had been previously surface-modified by the manufacturer.

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Abstract  

The oxidation of a precipitation-hardening (PH) steels is a rather unexplored area. In this study an attempt is made to estimate the oxidation mechanism and the kinetics that take place up to 850 °C. For this purpose specimens of the material under examination were isothermally heated at 725, 775, 800, 825, and 850 °C for 12 h in O2 atmosphere. The as-treated samples were examined with SEM and XRD, while kinetics were based on thermogravimetric (TG) results. From this examination it was deduced that the oxidation of this steel is accomplished at minimum three steps, following the changes of the scale morphology and the kinetics. After 850 °C although that the oxidation rate increases, the scale morphology does not change. From the calculations of the rate constant k p and the activation energy for the phenomena below 850 °C, it was deduced that the oxidation phenomena during this stage provides another barrier to the deterioration of the ferrous material.

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Abstract  

Alpha-tocopherol (vitamin E) is the most widely used antioxidant for edible oils. The present investigation presents its effect on the thermal degradation behavior of edible oils (sunflower, soybean, and their blend) through the use of dynamic thermogravimetry. The study is based on the comparison of activation energies of decomposition process which were subsequently calculated using preferred and reliable multiple-heating rate methods viz. Kissinger, Friedman, Ozawa–Flynn–Wall, and Coats–Redfern (modified). It is concluded that the role of alpha-tocopherol as antioxidant at higher temperature is nearly accomplished.

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thermogravimetry (TG), gas chromatography/mass spectrometry (GC/MS), or simple pyrolysis. Experimental General In general, reactions were carried out in a dry (all glassware was dried in an oven overnight at 120 °C

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Journal of Thermal Analysis and Calorimetry
Authors: Jorge López-Beceiro, José Pascual-Cosp, Ramón Artiaga, Javier Tarrío-Saavedra, and Salvador Naya

)Al(SO 4 ) 2 ·12H 2 O. It occurs naturally as the rare mineral tschermigite [ 5 ]. Thermogravimetry (TG) has been used to investigate thermal decomposition of alums and related compounds [ 6 – 8 ]. Nevertheless, in the case of ammonium alum, some of

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Journal of Thermal Analysis and Calorimetry
Authors: Ronaldo S. Nunes, Gilbert Bannach, José M. Luiz, Flávio J. Caires, Claudio T. Carvalho, and Massao Ionashiro

Th(IV) and Al(III), with EDTA [ 2 , 3 ]. The works reported the synthesis and characterization of the compounds by means of thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), X-ray powder

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Journal of Thermal Analysis and Calorimetry
Authors: Fillipe V. Rocha, Carolina V. Barra, Silmar J. S. Franchi, Adelino V. G. Netto, Antonio E. Mauro, and Regina C. G. Frem

], and biological activity of palladium(II) complexes [ 20 – 22 ], we present in this study the thermal investigation of tdmPz and compounds of the type [PdX 2 (tdmPz)] by means of thermogravimetry (TG) and differential thermal analysis (DTA

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