Thermal analysis of neuroleptic drugs and vitamins

The thermal decomposition of 41 drugs containing acetylsalicylic acid, 5-pyrazolone derivatives, the components stimulating the central nervous system, the Aviomarin, Glutamic acid, and Laxative chocolate tablets, and vitamins has been studied by employing the differential thermal analysis (DTA), thermogravimetry (TG), and differential TG (DTG) techniques. The possibility has been demonstrated to employ the DTA, TG, and DTG curves of their thermal decomposition for the identification of particular dosage forms and for the qualitative and quantitative monitoring of their composition. Based on the stages due to dehydration, decarboxylation, and formation of intermediate decomposition products, the content of the active components was determined in 17 of the drugs. The results of the determinations were in good agreement with those calculated from information supplied by the manufacturers.     

Kinetic modeling of Pt-catalyzed glycolaldehyde decomposition to syngas

Fundamental knowledge of the elementary reaction mechanisms involved in oxygenate decomposition on transition metal catalysts can facilitate the optimization of future catalyst and reactor systems for biomass upgrade to fuels and chemicals. Pt-catalyzed decomposition of glycolaldehyde, as the smallest oxygenate with alcohol and aldehyde functionality, was studied via a DFT-based microkinetic model. It was found that two decomposition pathways exist. Under conditions of low hydrogen surface coverage, the initial C-H bond breaking reaction to HOCH(2)CO* is prevalent, while under conditions of high hydrogen coverage, the rather unexpected O-H bond forming reaction to HOCH(2)CHOH* is more active (subsequent decomposition is energetically favorable from HOCH(2)CHOH*). Our results indicate the possibility that (de)hydrogenation chemistry is rate-controlling in many small polyoxygenate biomass derivatives, and suitable catalysts are needed. Finally, DFT was used to understand the increased decomposition activity observed on the surface segregated Ni-Pt-Pt bimetallic catalyst. It was found that the initial O-H bond breaking of glycolaldehyde to OCH(2)CHO* has an activation barrier of just 0.21 eV. This barrier is lower than that of any glycolaldehyde consuming reaction on Pt. These computational predictions are in qualitative agreement with experimental results.     

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.     

Monitoring of the Gas Phase Composition: A Prerequisite for Unravelling the Mechanism of Decomposition of Solids. Thermal decomposition of cobalt oxalate dihydrate

The complexity of the processes occurring during cobalt oxalate dihydrate (COD) decomposition indicates that an interpretation of the mechanism based only on the TG curve is of little value. Mass change alone does not allow deeper insight into all of the potential primary and secondary reactions that could occur. The observed mass changes (TG) and thermal effects (DTA/DSC) are a superposition of several phenomena and thus do not necessarily reflect COD decomposition alone. Investigation of the mechanism of decomposition requires the application of different simultaneous techniques that allow the qualitative and quantitative determination of the composition of the gaseous products. Composition of the solid and gaseous products of COD decomposition and heats of dehydration and oxalate decomposition were determined for inert, oxidizing and hydrogen-containing atmospheres. Contrary to previous suggestions about the mechanism of cobalt oxalate decomposition, the solid product formed during decomposition in helium contains not only metallic Co_met, but also a substantial amount of CoO (ca 13 mol%). In all atmospheres, the composition of the primary solid and gaseous products changes as a result of secondary gas-solid and gas-gas reactions, catalyzed by freshly formed Co_met. The course of the following reactions has been investigated under steady-state and transient conditions characteristic for COD decomposition: water gas shift, Fischer-Tropsch, CO disproportionation, CoO reduction by CO and H₂, Co_met oxidation under rich and lean oxygen conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

三线性直接分解法分析高维灰色体系

对于由多个两维测量数据组成的三维阵，本文提出一种新三线性直接分解方法。采用高维ＰＣＡ分解，从三维阵中直接提取抽象光谱和抽象浓度，再结合ＱＺ算法，唯一地确定混合物中各组分光谱的浓度。该方法可以排除其它未知组分的干扰，适用于高维灰色体系定性定量分析和多点校准。用模拟数据讨论了光谱分离度对该方法的影响，应用于混合维生素Ｂ１、Ｂ２和Ｂ６的荧光分析，求得的光谱和浓度与实验值吻合很好。     

Phase separation kinetics in mixtures of polymers and liquid crystals

Light scattering has been used to study phase separation kinetics in mixtures containing liquid crystals and epoxy resins. In the samples studied, phase separation was induced by the polymerization of the resins with an appropriate curing agent. Experiments were carried out at different compositions and at different temperatures. The results show that the kinetic mechanism of phase separation is composition dependent. For high liquid crystal content the data are in qualitative agreement with existing theories describing spinodal decomposition; at lower concentrations the mechanism is different. The physical properties of the resulting materials are independent of the decomposition mechanism. The data have also been analysed considering the scaling behaviour expected for late stages of phase separation in polyinduced meric mixtures. Samples obtained in a narrow concentration range, where the two kinetic mechanisms overlap, exhibit peculiar physical properties.     

酰胺和酰亚胺改性聚乙烯的热分解行为

聚乙烯 (ＰＥ)的化学改性已得到广泛应用 ,它能使ＰＥ获得新的物理化学或功能特性 ,如改进其表面粘合、亲水及吸湿、染色和印刷性质等 ,尤其在增加它与其它聚合物的相容性 ,制备共混材料时常常是必不可少的[1 ,2 ] .目前最方便和有效的方法是通过马来化聚乙烯用不同基团接枝来实现化学改性 ,由于改性后的ＰＥ需经熔融加工成制品 ,化学改性基团必须在加工温度 ( 1 70～2 0 0℃ )和时间内具有足够的热稳定性 ,因此观察它们在热加工条件下的热稳定性和热分解行为显得十分重要 .通常这种化学改性的程度 (改性基团含量 )很小 ,并且在加工温度下所…     

Reactive processes in gas phase Na(+)-iso-C3H7Cl collisions: experimental guided-ion-beam and ab initio studies of the reactions on the ground singlet potential surface of the system up to 12.00 eV

Reactive processes, taking place when sodium ions collide with neutral iso-C(3)H(7)Cl molecules in the 0.02-12.00 eV range of energies in the center of mass frame, have been studied using an octopole radiofrequency guided-ion-beam apparatus developed in our laboratory. A dehydrohalogenation reaction channel leading to Na(C(3)H(6))(+) formation has been observed up to 1.00 eV while another process producing NaHCl(+) continues up to 4.00 eV. Furthermore, C(3)H(7)(+) formation resulting from decomposition of the reactants, ion-molecule adducts, has also been observed as well as its decomposition into C(2)H(3)(+) on increasing collision energy. Cross-section energy dependences for all these reactions have been obtained in absolute units. The ab initio electronic structure calculations have been done at the MP2 level for the colliding system ground singlet potential surface, giving information on the reactive surface main topological features. From the surface reactants side to the products' one, different potential wells and barriers have been characterized and their connectivity along the reaction evolution has been established using the intrinsic-reaction-coordinate method, thus interpreting the dynamical evolution of the reactants' collision complex to products. Experimental results demonstrate that NaHCl(+) can be produced via different channels. Reaction rate constants at 308.2 K for both dehydrohalogenation reactions have been calculated from measured excitation functions. It has been also confirmed that the reactants adduct decomposition giving C(3)H(7)(+) and NaCl takes place on the same potential surface. A qualitative interpretation of the experimental results in terms of ab initio calculations is also given.     

The influence of various tablet components on thermal decomposition of some pharmaceuticals

Summary The thermal decomposition of tablet components used in the granulation and tableting of pharmaceuticals, and of more than ten of the mixtures frequently encountered in solid dosage forms was studied by thermogravimetric and differential thermal analysis. From the decomposition of these mixtures, which were of varied composition, the influence of mixtures of various tablet components on the thermal decomposition of pharmaceuticals was evaluated. Use can be made of the results to establish the conditions to be fulfilled by a compound if thermal methods are to be used for qualitative and quantitative control of the declared composition of a solid formulation.

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Der Einfluß verschiedener Tablettenbestandteile auf die thermische Zersetzung einiger Arzneimittel

Zusammenfassung Die thermische Zersetzung von Tablettenbestandteilen, die bei der Granulierung und Tablettierung von Arzneimitteln und in mehr als 10 solchen Gemischen oftmals festen Präparaten zugesetzt werden, wurden thermogravimetrisch und differential-thermisch analysiert. Aus der Zersetzung dieser verschieden zusammengesetzten Gemische wurde der Einfluß gemischter Tablettenbestandteile auf den thermischen Zerfall von Arzneimitteln ermittelt. Aus den Ergebnissen lassen sich die Bedingungen ableiten, die eine Verbindung erfüllen muß, damit sich thermische Methoden für die qualitative und quantitative Kontrolle der angegebenen Zusammensetzung eines festen Präparates eignen.

     

Standardless spectral analysis of independent mixture components: Experimental case studies

We applied recently proposed methods for mixture decomposition in statistically independent components (MILCA and SNICA) to solve practical problems in analytical spectroscopy. These methods aim at reconstructing the spectra of individual mixture components and their concentrations from linear mixtures. Here, they were applied to experimental standardless qualitative and quantitative analysis in UV and visible absorption spectroscopy. However, this family of methods can be coupled with almost any sort of spectroscopic measurements. The results are presented through a series of experimental case studies, including the analysis of major ecotoxicants, polyaromatic hydrocarbons.     

The application of thiosalts in analysis: A new scheme of qualitative analysis Part A

A brief outline is given of the new scheme of qualitative analysis for common elements based upon the decomposition of thiosalts.     

Experimental results and theoretical considerations on thermogravimetric decomposition reactions of chemical compounds under high vacuum

Investigations on thermogravimetric decomposition reactions under high vacuum have demonstrated that special attention should be paid to such factors as the sample size, the crucible form, the thickness of the layer in the crucible, the particle size of the probe material, etc. It is shown how the various influences can be eliminated by observing certain starting or test conditions. In addition to experiments on these specific influences, a comparison has been made of the degradation speeds of single crystals and crystal powders of chemical compounds.Results, which are complementary to the thermogravimetric measurements can be obtained with qualitative or quantitative determination of the gaseous decomposition products by mass spectrometric analysis. From these measurements the course of decomposition is followed by recording the partial pressure at the various individual masses. This method is particularly suitable for the study of thermal degradations which produce more than one decomposition product in the same step.     

Eigenanalysis of infrared mulitphoton decomposition kinetics

An eigenvalue/eigenvector analysis of the master equation for infrared multiphoton decomposition is used to derive a computational efficient means of analysing experimental data (such as fractional decomposition and, for multichannel reactions, branching ratios) to obtain laser absorption cross sections and information on gas/gas energy transfer. Reaction both during and after the pulse is incorporated, post-pulse collisional relaxation being found to be of both qualitative and quantitative importance in the interpretation of data. It is shown that fractional decomposition and branching ratios are essentially independent of the finer details of pulse shape, provided that the fluence remains fixed; it is am demonstrated that the analysis of the problem in terms of a single eigenvalue is inadequate.     

气相色谱-质谱法研究香叶基-β-D-吡喃葡萄糖苷的热裂解行为

为了研究香叶醇的糖苷类香料前体香叶基-β-D-吡喃葡萄糖苷的热裂解行为,在200,300,400 ℃条件下,分别采用 在线模式的裂解仪无氧裂解和离线模式的高温熔盐加热裂解,热解产生的物质均经毛细管气相色谱-质谱仪进行定性和定 量检测。根据实验结果,对香叶基-β-D-吡喃葡萄糖苷的裂解机理进行了初步探讨。实验发现,香叶基-β-D-吡喃葡萄糖 苷在200 ℃条件下裂解量很少;300 ℃条件下裂解产生大量香叶醇,而其他杂质较少;随着温度的升高,400 ℃条件下裂解 产生的副产物明显增加。实验结果表明以300 ℃条件下裂解效果最好。同时,香叶基-β-D-吡喃葡萄糖苷热裂解产生了特 征香味成分香叶醇,其裂解的基本反应是O-糖苷键的断裂。在试验的两种方法中,在线裂解模式实验方法先进,定性直接, 结果准确;离线裂解模式实验方法操作方便,简单易行,而且在定性基础上可以实现定量分析。     

The application of thiosalts in analysis : A new and more comprehensive scheme of qualitative analysis

The scheme of qualitative analysis based on the formation and decomposition of thiosalts has been enlarged by including within it practically all the basic radicles -which are likely to be met with in the analysis of ores and alloys, etc. Besides the rare elements already included in the original scheme rhodium, ruthenium, osmium, palladium, iridium, gallium, indium, rhenium, tantalum, niobium, germanium, scandium and the rare-earths and alkalis have been fitted into the more comprehensive scheme. An outline of procedures for the separation of metals into groups in the more comprehensive scheme of qualitative analysis is given.     

Acousto-spinodal decomposition of compressible polymer solutions: early stage analysis

The structure and dynamics of early stage kinetics of pressure-induced phase separation of compressible polymer solutions via spinodal decomposition is analyzed using a linear Euler-Cahn-Hilliard model and the modified Sanchez Lacombe equation of state. The integrated density wave and Cahn-Hilliard equations combine the kinetic and structural characteristics of spinodal decomposition with density waves arising from pressure-induced couplings. When mass transfer rate is slower that acoustic waves, concentration gradients generate density waves that cycle back into the spinodal decomposition dynamics, resulting in oscillatory demixing. The wave attenuation increases with increasing mass transfer rates eventually leading to nonoscillatory spinodal demixing. The novel aspects of acousto-spinodal decomposition arise from the coexistence of stable oscillatory density dynamics and the unstable monotonic concentration dynamics. Scaling laws for structure and dynamics indicate deviations from incompressible behavior, with a significant slowing down of demixing due to couplings with density waves. Partial structure factors for density and density-concentration reflect the oscillatory nature of acousto-spinodal modes at lower wave vectors, while the single maximum at a constant wave vector reflects the presence of a dominant mode in the linear regime. The computed total structure factor is in qualitative agreement with experimental data for a similar polymer solution.     

Evaluation of laser induced breakdown spectroscopy for the determination of macronutrients in plant materials

Laser induced breakdown spectroscopy (LIBS) has become an analytical tool for the direct analysis of a large variety of materials in order to provide qualitative and/or quantitative information. However, there is a lack of information for LIBS analysis of agricultural and environmental samples. In this work a LIBS system has been evaluated for the determination of macronutrients (P, K, Ca, Mg) in pellets of vegetal reference materials. An experimental setup was designed by using a Nd:YAG laser operating at 1064 nm and an Echelle spectrometer with ICCD detector. The plasma temperature was estimated by Boltzmann plots and instrumental parameters such as delay time, lens-to-sample distance and pulse energy were evaluated. Certified reference materials as well as reference materials were used for analytical calibrations of P, K, Ca, and Mg. Most results of the direct analysis of plant samples by LIBS were in reasonable agreement with those obtained by ICP OES after wet acid decomposition.     

Two-dimensional surrogate Hamiltonian investigation of laser-induced desorption of NO/NiO(100)

The photodesorption of NO from NiO(100) is studied from first principles, with electronic relaxation treated by the use of the surrogate Hamiltonian approach. Two nuclear degrees of freedom of the adsorbate-substrate system are taken into account. To perform the quantum dynamical wave-packet calculations, a massively parallel implementation with a one-dimensional data decomposition had to be introduced. The calculated desorption probabilities and velocity distributions are in qualitative agreement with experimental data. The results are compared to those of stochastic wave-packet calculations where a sufficiently large number of quantum trajectories is propagated within a jumping wave-packet scenario.