共查询到20条相似文献,搜索用时 15 毫秒
1.
Ana Paula Barrêto Gomes Lidiane Pinto Correia Mônica Oliveira da Silva Simões R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,88(2):383-387
The objective of this work was to develop
and validate a fast and reproducible method to determine the concentration
of metronidazole in drug substance and tablets. The samples were analyzed
by dynamic thermogravimetry, using 10, 20, 40, 60 and 80°C min–1
heating rates in nitrogen and in nitrogen with synthetic air. Obtained data
were used in the Antoine and Langmuir equations in order to have the pressure
curves. Vapor pressure curves of drug and tablet of metronidazole were evaluated
using the mathematical indexes of difference factor, f
1,
and similarity factor, f
2,
to compare their profiles. The data showed that there is no significant difference
between the vapor pressure profiles of drug and tablet of metronidazole in
both environmental conditions, which confirms that the process is really vaporization.
The concentration of metronidazole was determined in the raw material and
tablets of the drug. 相似文献
2.
The objective of this work was to develop and validate a fast and reproducible method which is able to determine the concentration
of ketoconazole in raw materials and tablets. The samples were analyzed by dynamic thermogravimetry at heating rates of 10,
20, 40, 60 and 80°C min−1 in nitrogen and nitrogen-synthetic air mixture. The concentrations of ketoconazole in the raw material and in the tablets
were obtained from the vapor pressure curves. The data showed that there is no significant difference between the vapor pressure
profiles of ketoconazole itself and in its tablet in both studied environmental conditions confirming that the process is
really vaporization. The concentration of ketoconazole was determined in the raw material and tablets of the drug. 相似文献
3.
Chatterjee K. Dollimore D. Alexander K. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):629-639
Hydroxy benzoic acids were subjected to rising temperature thermogravimetric analysis. After optimizing the procedural variables,
the kinetics of decomposition was determined and methyl paraben was taken as the calibration compound to characterize the
evaporation patterns for the ortho and meta derivatives. The E
act values for ortho, meta and para derivatives were 64.8, 78.2, and 119.1 kJ mol–1, respectively. The Antoine and Langmuir equations were utilized to determine the coefficient of evaporation k, which was 124525±0.8, units being in the SI system. The vapor pressure plots were generated for the ortho and meta derivatives; ΔH
vap for these two compounds were obtained as 66.7 and 80.4 kJ mol–1, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
A new analytical method based on thermogravimetry and applied to chemically functionalized surfaces is proposed. The mass losses of surfaces modified with alkoxysilane reagents, Sup-CH2CH2CH2?R (Sup=support andR=Cl, SH, NH2, NHCONH2, NHNHCOCH3 or (CH2)4NH), are interpreted by considering the physically adsorbed water, the silanol groups and the organic moiety. The elemental analyses calculated from these data are in agreement with those obtained by classical elemental analysis. The method is quick and reproducible, and requires the use of only a few milligrams of material. 相似文献
5.
H. A. Schneider 《Journal of Thermal Analysis and Calorimetry》1993,40(2):677-687
Due to the complex character of the thermal degradation of polymers as a solid-gas chain reaction, an unequivocal kinetic
characteirzation is possible only for stationary states of both radical concentration and reaction mechanism. These conditions
are hardly realizable in non-isothermal thermogravimetry. Additional the weight losses are depedent on the volatility of the
reaction products. That is not always certain in polymer degradation. As a consequence the deduced ‘kinetic parameters’ are
not unequivocal. They are conversion and heating rate dependent and may be influenced by sample shape and size. Thus the ‘kinetic
parameters’ are in fact from the point of view of mathematics the fitting parameters of a ‘rate equation’ like relation, specific
for the used reaction conditions only. From the point of view of chemical kinetics they are neither attributable to a determined
reaction mechanism nor can they be used for predictions.
Dedicated to the 70th Anniversary of Dr. Jo Flynn 相似文献
6.
Stefano Vecchio Alessia Catalani Vanessa Rossi Mauro Tomassetti 《Thermochimica Acta》2004,420(1-2):99-104
The thermal behaviour of acetanilide (Ac) and two of its analogues, namely the para-ethoxyacetanilide (p-Eto Ac) and the para-bromoacetanilide (p-Br Ac), which are used as analgesics in the pharmaceutical industry was studied with a simultaneous TG/DSC unit. The examined analgesics showed two endothermic DSC peaks due to melting and vaporization. By combining the experimental TG data with the corresponding reference vapour pressure data obtained with the Antoine equation the plot of P versus v was derived. From the slope of this equation the constant k-value was determined for Ac. Then, using the same k-value the vapour pressures of p-Eto Ac and p-Br Ac were determined in the same temperature range. The vaporization enthalpies for all the studied compounds were obtained from different methods and a very good agreement was found. Vaporization follows a zero-order kinetics. The activation energy of vaporization (Evap) was calculated from the dynamic TG experiments, using the Arrhenius equation. 相似文献
7.
8.
A. Hazra K. Alexander D. Dollimore A. Riga 《Journal of Thermal Analysis and Calorimetry》2004,75(1):317-330
The present study was aimed at determining the kinetics of evaporation and establishing vapor pressure curves for both single and multi-component systems by thermogravimetry (TG) and differential scanning calorimetry (DSC). Essential oils (e.g. lavender oil, orange oil, clove oil and eucalyptus oil, etc.) are typically multi-component systems consisting of various volatile pure components (e.g. linalyl acetate, limonene, cinnamaldehyde, etc.) which resemble single component systems. In this study linalyl acetate was taken as the calibration compound for TG. The vapor pressure curves for the pure substances were plotted using TG and vapor pressure plots for clove oil and eucalyptus oil were constructed using DSC. The thermodynamic and kinetic parameters of the pure compounds were compared to that of the multi-component systems to quantitatively and qualitatively measure the influence of different compounds on each other. The k-value from the vapor pressure data for linalyl acetate was calculated as 112006 Pa kg0.5mol0.5s-1 m-2 K-0.5. The vapor pressure values were used to determine the Antoine constants using the SPSS 10.0 software.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
9.
Vapor pressure is one of the important properties necessary for process design. Antoine equation has been widely used to evaluate the vapor pressures. This article deals with the proposal of a method for predicting the Antoine constants using a group contribution method. The 1817 compounds treated here are grouped into six classes. The group contribution parameters for each class have been determined using a regression analysis. The group contribution method with help of experimental normal boiling point has good results for predicting the vapor pressures. 相似文献
10.
Thermogravimetric Study of Volatile Precursors For Chemical Thin Film Deposition. Estimation of vapor pressures and source temperatures 总被引:1,自引:0,他引:1
Niskanen A. Hatanpää T. Ritala M. Leskelä M. 《Journal of Thermal Analysis and Calorimetry》2001,65(3):955-964
Normal pressure thermogravimetry (TG) measurements were used to study the sublimation behavior of several volatile metal compounds,
used as metal precursors in thin film fabrication by chemical vapor phase methods, like atomic layer deposition (ALD) and
chemical vapor deposition (CVD). The results indicated that dynamic TG measurements may be used to find correct source temperatures
to be used in an ALD reactor: a good correlation between the source temperatures used in ALD and temperatures corresponding
to mass losses of 10 and 50% in TG was verified. It was also found that isothermal TG measurements offer a simple way for
the vapor pressure measurements which otherwise are not trivial for solids with only moderate volatility.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
The vapour pressures of n-octane have been measured using comparative ebulliometry with water as the reference fluid. The results cover the temperature and pressure range (323.2 K, 6.7 kPa) to (563.3 K, 2301.7 kPa) and have been described by a Wagner style equation with a fractional standard deviation of 3.3×10−5 in the vapour pressure. The critical pressure pc was treated as an adjustable parameter and the value of pc=2482 kPa was obtained using the literature value for the critical temperature. An Antoine equation that describes the results below a pressure of 142 kPa with a standard deviation of 1.4 mK in the condensation temperature has also been obtained. 相似文献
12.
Fast method for the experimental determination of vaporization enthalpy by differential scanning calorimetry 总被引:1,自引:0,他引:1
Cedeńo Fidel. O. Prieto Maria. M. Espina Aranzazu García Jose. R. 《Journal of Thermal Analysis and Calorimetry》2003,73(3):775-781
A simple method is proposed to estimate the vaporization enthalpy of the palmitic acid (hexadecanoic acid) at its normal boiling
temperature. Differential scanning calorimetry (DSC) was the technique used to directly measure these thermodynamic properties.
The advantages of this method are its speed and small amount of sample required. In order to avoid evaporation and to ensure
equilibrium conditions, the experiments were carried out including a-alumina in contact with the fatty acid. The effect of
the alumina concentration is discussed. The obtained experimental data (Tbp=625.4±0.5 K, Dvap
H=237.6±5.9 J g-1) is compared with that obtained by using thermodynamic equations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Tomoya Yoshinari Hiroyuki Ohashi Ryoji Abe Rena Kaigome Hideo Ohkawa Yoshiko Sugita-Konishi 《Analytica chimica acta》2015
Quenchbody (Q-body) is a novel fluorescent biosensor based on the antigen-dependent removal of a quenching effect on a fluorophore attached to antibody domains. In order to develop a method using Q-body for the quantitative determination of deoxynivalenol (DON), a trichothecene mycotoxin produced by some Fusarium species, anti-DON Q-body was synthesized from the sequence information of a monoclonal antibody specific to DON. When the purified anti-DON Q-body was mixed with DON, a dose-dependent increase in the fluorescence intensity was observed and the detection range was between 0.0003 and 3 mg L−1. The coefficients of variation were 7.9% at 0.003 mg L−1, 5.0% at 0.03 mg L−1 and 13.7% at 0.3 mg L−1, respectively. The limit of detection was 0.006 mg L−1 for DON in wheat. The Q-body showed an antigen-dependent fluorescence enhancement even in the presence of wheat extracts. To validate the analytical method using Q-body, a spike-and-recovery experiment was performed using four spiked wheat samples. The recoveries were in the range of 94.9–100.2%. The concentrations of DON in twenty-one naturally contaminated wheat samples were quantitated by the Q-body method, LC-MS/MS and an immunochromatographic assay kit. The LC-MS/MS analysis showed that the levels of DON contamination in the samples were between 0.001 and 2.68 mg kg−1. The concentrations of DON quantitated by LC-MS/MS were more strongly correlated with those using the Q-body method (R2 = 0.9760) than the immunochromatographic assay kit (R2 = 0.8824). These data indicate that the Q-body system for the determination of DON in wheat samples was successfully developed and Q-body is expected to have a range of applications in the field of food safety. 相似文献
14.
K. M. Drljević-Djurić M. L. Avramov Ivić S. D. Petrović D. Ž. Mijin M. B. Jadranin 《Russian Journal of Electrochemistry》2011,47(7):781-786
The aim of this study was to present the quantitative determination of midecamycin at a gold electrode in 0.05 M NaHCO3 using cyclic linear sweep voltammetry. It was found that the value of the oxidative peak of pure midecamycin at 0.85 V vs.
SCE at a scan rate of 50 mV s−1 is a linear function of the concentration in the range 0.1693–0.3289 mg cm−3. The value of its reductive peak at 0.3 V vs. SCE is a linear function of the concentration in the range 0.11396–0.3802 mg
cm−3. HPLC analysis of the bulk of electrolyte confirmed the data obtained by analysis of the current peak values concerning the
correlation with each investigated concentration of midecamycin. By MS spectrometry no degradation products were found in
electrolyte during its quantitative determination. 相似文献
15.
F. Paulik S. Gál K. Mészáros Szécsényi 《Journal of Thermal Analysis and Calorimetry》1994,42(2-3):425-435
A method is described for the microdistillation of liquids using quasi-isothermal quasi-isobaric thermogravimetry. The liquidus curve determined under quasi-equilibrium conditions gives useful information about the composition and some thermal properties of the sample. The method could be attractive for the mineral oil, lacquer, biological and organochemical industry. 相似文献
16.
17.
Siberian Medical University, Siberian. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 506–507, May–June, 1995. Original article submitted December 27, 1993. 相似文献
18.
天然产物液体组分饱和蒸汽压间接测定实验方法 总被引:1,自引:0,他引:1
根据物理化学中的相平衡体系热力学理论设计了间接测定天然产物液体组分饱和蒸汽压数据的实验方法,采用改进的Ellis或Rose平衡釜测定不同压力下高浓度的天然产物溶液汽液平衡数据,推算不同温度下天然产物液体组分的饱和蒸汽压,回归出Antoine方程的各参数A,B,C,建立天然产物液体组分饱和蒸汽压与温度的关联式.应用该方法测定了蒎烷、对孟烷与长叶烯的饱和蒸汽压,所得结果与文献值吻合良好,为天然产物液体组分饱和蒸汽压的实验测定与关联提供了一种便捷的途径. 相似文献
19.
20.
Formation of inclusion complexes with cyclodextrins (CDs) is known to enhance guest solubility in aqueous medium. Different techniques allow determining the evolution in solubility of individual guest compounds. However, examination of mixtures solubility encapsulated in CDs is still a challenge. This is mainly related to the difference in the response of mixture components to the applied technique or to the fact that most of the conventional methods examine the signal of an individual constituent of the mixture. Thus, applying current techniques may not reflect the behavior of the whole mixture. Here, we used for the first time Total Organic Carbon (TOC) analysis to explore and assess the efficiency of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) to enhance the solubility of natural complex mixtures such as essential oils (EOs). Phase solubility studies were performed for eleven EOs with HP-β-CD. The TOC method has provided good validation parameters for linearity, precision and accuracy. For further validation of the method, phase solubility studies were performed with HP-β-CD for eugenol, as a model EO component. The eugenol solubility was determined by UV–Visible and TOC analyses in order to compare the results. Data obtained from both methods were similar (p < 0.05), thereby proving the effectiveness of the developed TOC method. Finally, the phase solubility diagrams of EOs showed that the solubilizing potential of CD increased proportionally with the decrease in EO intrinsic solubility. Results proved that TOC could be successfully applied to investigate CD/guest inclusion complexes and is expected to have a broad range of applications in the field of mixtures encapsulation. 相似文献