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Abstract
The thermochemical behaviour of betaine and betaine monohydrate was investigated under two degradation conditions. Betaine was heated up to 700°C at 10°C min–1 in air and nitrogen flows and the evolved gas was analysed with the combined TG-FTRIR system. The evolved gas from betaine pyrolysis at 350 and 400°C was analysed by gas chromatography using mass-selective detection (Py-GC/MSD). In addition, the electron impact mass spectra of betaine and betaine monohydrate were measured.Esterification is one of the most important pyrolytic processes involving beta- ines. Even glycine betaine can change to dimethylglycine methyl ester via intermolecular transalkylation by heating. Trimethylamine, CO2, and glycine esters were the main degradation products. Small amounts of ester type compounds evolved both in pyrolysis and with TG-FTIR. The monohydrate lost water between 35 and 260°C while the main decomposition took place at 245-360°C. The residual carbon burnt in air to CO2 up to a temperature 570°C.
Abstract
The cefadroxil (Cef) complexes with transition divalent metals of the formula MCefnH2O (where n=2 for M=Cu2+, Ni2+, Zn2+ and n=3 for Co2+) and CdCef1.54H2O were prepared and characterized by elemental and infrared spectra. The thermal analysis of the investigated complexes in air atmosphere was carried out by means of simultaneous TG-DSC technique. During heating in air they lose bound water molecules and then decompose to oxides: Co3O4, NiO, CuO, ZnO and CdO. The CdCef1.54H2O complex forms probably an intermediate product Cd2OSO4. The combined TG-FTIR technique was employed to study of decomposition pathway of the investigated complexes. The first mass loss step is the water loss of the complexes. Next, decomposition of cefadroxil ligand occurs with evolution of CO2 and NH3. At slightly higher temperature COS is observed according to decomposition of cephem ring. Additionally, as decomposition gaseous products: HCN, HNCO (HOCN), H2CNH, CO, SO2, hydrocarbons and carbonyl compounds were observed. The formation of metal sulfates is postulated as solid intermediate product of decomposition in the argon atmosphere.
Abstract
Triprolidine hydrochloride (C19H22N2·HCl·H2O) (TPH) is a well-known antihistamine drug which is reported as being photosensitive. The thermal stabilities of TPH and of 1:1 molar and 1:1 mass ratio physical mixtures of TPH with β-cyclodextrin (BCD) and with glucose have been examined using DSC, TG and TG-FTIR, complemented by X-ray powder diffraction (XRD) and infrared spectroscopic (IR) studies. Thermal studies of the solid TPH/BCD mixtures indicated that interaction between the components occurs and it is possible that the TPH molecule may be least partially accommodated in the cavity of the BCD host molecule. XRD results support this indication of inclusion. The results of molecular modelling suggest that TPH is most likely to be accommodated in the BCD cavity as a neutral triprolidine molecule with the toluene portion of the molecule preferentially included in the cavity. The results obtained illustrate the general stability of TPH. The study has also shown TPH to be compatible with both glucose and BCD, which are potential excipients both in solid and liquid dosage forms. The presence of these excipients in dosage forms will thus not adversely affect the stability and the therapeutic efficacy of TPH.
Abstract
Thermal decomposition of a mixed valence copper salt, Na4[Cu(NH3)4][Cu(S2O3)2]2·0.5NH3 (1) prepared from pentahydrates of sodium thiosulfate and copper sulphate of various molar ratios in 1:1 v/v aqueous ammonia solution, has been studied up to 1,000 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR), in comparison. Compound 1 releases first but very slowly some of the included ammonia till 170 °C, then simultaneously ammonia (NH3) and sulphur dioxide (SO2) from 175 to 225 °C, whilst the evolution of SO2 from thiosulfate ligands continues in several overlapping stages until 410 °C, and is escorted by explicit exothermic heat effects at around 237, 260, 358 and 410 °C. The former two exothermic DTA-peaks correspond to the simultaneous degradation and air oxidation processes of excess thiosulfate anions not reacted by formation of copper sulfides (both digenite, Cu1.8S and covellite, CuS, checked by XRD) and sodium sulfate, while the last two exothermic peaks are accompanied also by considerable mass gains, as the result of two-step oxidation of copper sulfides into various oxosulfates. The mass increase continues further on until 580 °C, when the sample mass begins to decrease slowly, as a continuous decomposition of the intermediate copper oxosulfates, indicated also by re-evolution of SO2. At 1,000 °C, a residual mass value of 64.3% represents a stoichiometric formation of CuIIO and anhydrous Na2SO4.
Abstract
The thermal decomposition of SEX in a nitrogen atmosphere was studied by coupled thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and by pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). The TG curve exhibited two discrete mass losses of 45.8% and 17.8% respectively, at 200 and 257–364°C. The evolved gases identified as a result of the first mass loss were carbonyl sulfide (COS), ethanol (C2H5OH), ethanethiol (C2H5SH), carbon disulfide (CS2), diethyl sulfide ((C2H5)2S), diethyl carbonate ((C2H5O)2CO), diethyl disulfide ((C2H5)2S2), and carbonothioic acid, O, S, diethyl ester ((C2H5S)(C2H5O)CO). The gases identified as a result of the second mass loss were carbonyl sulfide, ethanethiol, and carbon disulfide. Hydrogen sulfide was detected in both mass losses by py-GC-MS, but not detected by FTIR. The solid residue was sodium hydrogen sulfide (NaSH).
SEX was adsorbed onto activated carbon, and heated in nitrogen. Two discrete mass losses were still observed, but in the temperature ranges 100–186°C (7.8%) and 186–279°C (11.8%). Carbonyl sulfide and carbon disulfide were now the dominant gases evolved in each of the mass losses, and the other gaseous products were relatively minor. It was demonstrated that water adsorbed on the carbon hydrolysed the xanthate to cause the first mass loss, and any unhydrolysed material decomposed to give the second mass loss.
) by Using TG, FTIR and NMR. Journal of Thermal Analysis and Calorimetry, v. 85, p. 173–177, 2006.
, collection procedure was repeated four times. The crude product was recrystallized from ethanol to afford 190.30 g (69.3% yield) of 4-nitrophthalimide as yellow crystals, mp 203 °C (DSC). ([ 6 ], 198 °C), decomposition onset 203 °C (TG): FTIR (ATR, cm −1
Joseph D. Menczel and R. Bruce Prime (eds): Thermal analysis of polymers fundamental and applications
Published by John Wiley and Sons Inc. (688 pp)
-MS), TG-FTIR, and TG-DTA] in details which field is the most dynamically developing ones recently. The following section (Chap. 4) introduces thermomechanical analysis (TMA) and thermodilatometry (TD) by Harvey E. Bair, Ali E. Akinay, Joseph D
difficult to conclude anything based only in esters boiling points, for example, and there is no evidence of decomposition processes. Together with TG/FTIR data, some remarks can be done. These studies also tested biodiesels thermal behavior under
combustion properties were evaluated through microscale combustion calorimetry (MCC) experiment. In addition, TG, Real Time FTIR, and TG-FTIR were used to investigate the thermal degradation process of the materials. SEM and Raman diffusion measurements were
