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Determination of the reaction heat and studies of thermodynamic functions

Hydrolytic polymerization of chromium(III) at relatively high concentrations by microcalorimetry

Journal of Thermal Analysis and Calorimetry
Authors: Lu Chengxue, Yu Xiufang, and Zhang Honglin

The hydrolytic polymerization of Cr3+ at relatively high concentrations was studied by microcalorimetry. The thermal curves were determined with a 2277 thermal activity monitor. From the curves, the identified reaction heats (δrH m σ), hydrolysis constants (K) and thermodynamic functions (δrS m σrH m σ) were calculated at different temperatures.

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Abstract  

A study on extraction of thorium with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (PMBP)-loaded polyurethane foam is described. Open-cell polyurethane foam has proved to be effective as supporting material for PMBP. Thorium nitrate can be quantitatively extracted by PMBP-loaded polyurethane foam over a wide pH range. The effect of equilibrium time, pH, thorium concentration, various anions and flow-rate on the extraction efficiency of thorium is examined. A technique of extraction chromatography column with PMBP foam cylinder has been developed for trace thorium analysis of bulky water samples.

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Journal of Thermal Analysis and Calorimetry
Authors: Zhenrong Lu, Yuanchen Ding, Ying Xu, Shuhua Chen, and Yunpeng Yu

Abstract  

The thermal behaviors of [1,1,1-trifluro-3-(2-thenoyl)-acetonato]copper(II) Cu(TTA)2 and its adducts with pyridine Cu(TTA)2(Py)2, 2,2'-bipyridine Cu(TTA)2(Bpy), quinoline Cu(TTA)2(Ql)2, and dimethyl sulfoxide Cu(TTA)2(DMS) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC technique. The results showed that the evolution of the solvent molecules generally proceeded before the release of TTA in different ways according to their structures. The Cu(TTA)2(Bpy) exhibited a unique decomposition pattern due to its distinctive structure. The dependences of activation energy on extent of reaction for all the stage of each compound were determined by using an isoconversional method, Flynn-Wall-Ozawa equation, which show E values varied with reaction progress, indicating the complexity of these decomposition reactions. In addition, the values of activation energy E for TTA molecules evolution are generally higher than that for the solvent molecules release.

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Abstract  

Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)3 and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)2 and its adducts with pyridine, Ni(detp)2(py)2 or 4-methylpyridine, Ni(detp)(mpy)2 in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate. The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two ligands are of different type.

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Abstract

The thermal behavior of the anticancer drug-irinotecan was measured by Thermogravimetry–Differential thermal analysis (TG–DTA) to explore the application of TG–DTA in nanomedicine firstly. The TG–DTA result showed that the irinotecan was oxidized completely before 700 °C. When irinotecan was loaded onto nanosized mesoporous silica spheres, the loading capacity for irinotecan measured by TG–DTA was about 9.11% in the irinotecan/mesoporous SiO2 composite, similar to the typical UV–Vis spectra results (10.5%), which showed that TG–DTA characterization provided an alternative method to determine the drug loading amount on inorganic carriers. Secondly, Thermogravimetry–Differential scanning calorimetry–Mass Spectrometry coupling techniques (TG–DSC–MS) were used to characterize the hydrogen adsorption temperature and capacity of TiCr1.2 (V-Fe)0.6 alloy. The MS result showed that the released region of hydrogen was 250–500 °C, which was consistent with the TG–DSC results. Lastly, TA–MS combined with pulse thermal analysis (PulseTA) were used for a simultaneous characterizing study in the changes of mass, determination and quantitative calibration of the evolved nitrogen formed during the thermal decomposition of the InN powder. The results showed that relative error of this method between measured value and theoretical value was 2.67% for the quantitative calibration of evolved N2. It shows that TA–MS combined with PulseTA techniques offer a good tool for the quantification of the evolved nitrogen in the InN powder.

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Abstract  

Orthorhombic structural perovskite NdCrO3 nanocrystals with size of 60 nm were prepared by microemulsion method, and characterized by XRD, TEM, HRTEM, SEM, EDS and BET. The catalytic effect of the NdCrO3 for thermal decomposition of ammonium perchlorate (AP) was investigated by DSC and TG-MS. The results revealed that the NdCrO3 nanoparticles had effective catalysis on the thermal decomposition of AP. Adding 2% of NdCrO3 nanoparticles to AP decreased the temperature of thermal decomposition by 87° and increased the heat of decomposition from 590 to 1073 J g−1. Gaseous products of thermal decomposition of AP were NH3, H2O, O2, HCl, N2O, NO, NO2 and Cl2. The mechanism of catalytic action was based on the presence of superoxide ion O2 on the surface of NdCrO3, and the difference of thermal decomposition of AP with 2% of NdCrO3 and pure AP was mainly caused by the different extent of oxidation of ammonium.

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Hydroponic studies were conducted to investigate the role of iron plaque on transport and distribution of chromium (Cr) by rice seedlings. Microscopical observations indicate that iron plaque developed quickly at the root surface of rice seedlings, but the distribution of iron plaque was more intense near root base and less towards root tip. Results showed that rice seedlings exposed to Cr(III) depicted significantly higher capacity for Cr accumulation in plant tissues than Cr(VI) in the presence of iron plaque. However, transport of Cr within plant cells was more evident in Cr(VI) treatment with iron plaque than Cr(III) treatment. Results also showed that there are significant impact on transport of K, Mn and Zn in rice seedlings treated with Cr(VI) in the presence of iron plaque, while significant effect on transport of Mn and Zn were observed in Cr(III)-treated rice seedlings. Results from detached root test provide additional evidence to confirm the presence of iron plaque, that had different impact on Cr uptake when Cr(VI) or Cr(III) was supplied.

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Abstract

Calycanthine is an important class of alkaloids extracted and isolated from the roots, leaves, flowers and fruits of Chimonanthus praecox. In this work, the UPLC-MS/MS method was used for determination of calycanthine in rat plasma, and the pharmacokinetics in rats were investigated. Midazolam was used as an internal standard (IS), and methanol precipitation method was used to pretreatment the rat plasma samples. Chromatographic separation was achieved on a UPLC BEH C18 (50 × 2.1 mm, 1.7 μm) column with the mobile phase of methanol- 0.1% formic acid aqueous solution with gradient elution. Multiple reaction monitoring (MRM) mode with positive ionization was applied for quantitative analysis, m/z 347.3 → 246.7 and 326.2 → 291.4 for calycanthine and IS, respectively. The results indicated that within the range of 1–200 ng/mL, linearity of calycanthine in rat plasma was good (r > 0.995), and the lower limit of quantification (LLOQ) was 1 ng/mL. Accuracy range was between 90.6 and 109.4%, precision (RSD) of calycanthine was less than 14%. The matrix effect was between 97.9% and 105.4%, the recovery was better than 85.6%. The developed UPLC-MS/MS method was successfully applied in the pharmacokinetics of calycanthine in rats after oral and intravenous administration. The absolute bioavailability of the calycanthine was 37.5% in rats.

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Abstract  

A novel extractant, N, N-didecanoylpiperazine (DDPEZ), was synthesized for the first time. The extraction of U(VI) by DDPEZ from aqueous nitric acid media in carbon tetrachloride has been studied. The dependence of extraction distribution ratio on concentration of aqueous nitric acid, extractant, salting-out agent and temperature was investigated and the enthalpy of the extraction was calculated.

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Thermal decomposition of the carbon nanotube/SiO2precursor powders

Thermal analysis coupled with mass spectrometry

Journal of Thermal Analysis and Calorimetry
Authors: H. Yu, C. Lu, T. Xi, L. Luo, J. Ning, and C. Xiang

Summary  

TG-DSC-MS (thermogravimetry-differential scanning calorimetry-mass spectrometry) coupling techniques were used to make a simultaneous characterizing study for the thermal decomposition process of the carbon nanotube (CNT)/SiO2precursor powders prepared by rapid sol-gel method. The thermal stability of the CNT and the SiO2pure gel were investigated by TG-DSC. The results showed that the oxidation of CNT began from 530 and combusted at about 678C at the heating rate of 10C min-1in air. Moreover, the faster the heating rate, the higher the temperature of CNT combustion. The appropriate calcinations temperature of the CNT/SiO2precursor powders should be held for 1 h at 500C.

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