Thermal decomposition of RDX/AP by TG–DSC–MS–FTIR

The method of TG–DSC–MS–FTIR simultaneous analysis has been used to study the thermal decomposition mechanism of the RDX/AP (1/2) mixture. TG–DSC showed that there were two mass loss processes for thermal decomposition of RDX/AP. The first one was mainly ascribed to the thermal decomposition of RDX. Addition of AP to RDX causes decomposition to take place abruptly, after melting, resulting in a very sharp and strong peak at lower temperature. The apparent activation energies, calculated by model-free Friedman method, of this process were negative. The second mass loss process of RDX/AP was confirmed to be the thermal decomposition of AP, catalyzed by RDX. This process can be divided into three stages, which were an nth-order autocatalytic and two one-dimensional diffusion stages, respectively. There was a competition among the formation reactions of N₂O, HNCO, and HCl for the first stage and between NO₂ and N₂O for the later two stages. The production of N₂O dominated in the second stage, while NO₂ did in the third stage.     

Study of the MS response by TG–MS in an acid mine drainage efflorescence

The aim of this study is to employ a thermogravimetric analyzer coupled to a mass spectrometer to research into the influence of heating rate and sample mass on the response of the detector. That response is examined by means of a particular efflorescence taken from an acid mine drainage environment. This mixture of weathered products is mainly composed by secondary sulfate minerals, which are formed in evaporation conditions, appearing as efflorescence salts. Thermogravimetry coupled to mass spectrometry has been used to analyze the three main loss steps that happen when this combination of minerals is heated from 30 to 1,100 °C. This inorganic material is based on a mixture of hexahydrite, zinc sulfate hexahydrate, apjonite, gypsum, plumbojarosite, calcite, quartz, and magnetite. While heating, three main effluent gases evolved from this efflorescence. At a standard heating rate of 10 °C/min, loss of water (dehydration) occurred over 30–500 °C in four major steps, loss of carbon dioxide (decarbonisation) occurred over 200–800 °C in three steps, and loss of sulfur trioxide (desulfation) occurred over 400–1,100 °C in three steps. According to the results, thermal analysis is an excellent technique for the study of decomposition in these systems.     

Elastic organic–inorganic hybrid aerogels and xerogels

Novel aerogels and xerogels with methylsilsesquioxane (MSQ, CH₃SiO_1.5) networks have been prepared by a modified sol–gel process using surfactant and urea as a phase-separation inhibitor and as an accelerator for the condensation reaction, respectively. Optimized aerogels dried under a supercritical condition not only showed the similar properties as conventional pure silica aerogels such as high transparency and porosity etc, but also demonstrated outstanding mechanical strength against compression; the aerogel drastically shrank upon loading and then recovered when unloaded, which is called a “spring-back” behavior. On ambient pressure drying, the wet gel also exhibited the similar response against compression stress originated from the capillary pressure, and thus xerogels with the comparative structure and properties to those of corresponding aerogels have also been obtained. This unusual mechanical behavior is attributed to the trifunctional flexible networks of MSQ, low silanol concentration which prevents the irreversible shrinkage, and high concentration of a hydrophobic methyl group directly attached to every silicon atom which helps re-expansion after the temporal shrinkage.     

TG–DSC analysis of pyrolysis process of two Chinese oil shales

According to the recommendations developed by the Kinetics Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC), non-isothermal pyrolysis experiments were carried out to analyze and compare two types of oil shale from the northeast of China using simultaneous differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis at temperatures ranging from 40 to 850 °C. The pyrolysis process of oil shale begins with the evaporation of small molecular substances, then continues by the pyrolysis of kerogen, and finally ends mainly with the complete decomposition of carbonates. In this whole process, almost 36 % of overall pyrolytic heat was used for the pyrolysis of kerogen. When retorting air-dried basis oil shale below 520 °C, a considerable proportion of the heat required will have to be used mainly for the evaporation of small molecular substances below 185 °C. Specific heat capacities of two oil shale semicokes were measured below 500 °C by DSC method, showing that specific heat capacity of semicoke will increase with the increase of the temperature, and carbonization of kerogen can bring about a further positive effect on it. Coats–Redfern method was used to calculate kinetic parameters in three pyrolysis stages.     

Study on thermal degradation of cattlehide collagen fibers by simultaneous TG–MS–FTIR

Leather was useful materials since dawn of human history for excellent properties, but thermal degradation mechanism was not very clear yet. In this paper, much progress has been made in elucidating the thermal stability and thermal degradation mechanism by thermoanalytical study in argon. Thermogravimetric analysis simultaneously coupled with mass spectrometry and Fourier transform infrared spectrometry was employed to study the thermal degradation of cattlehide collagen fibers through in-depth analysis of the evolved gas. Thermogravimetry analyses carried out on sample, deprived from any residual catalyst and highlighted a two-step thermal degradation. New evidence demonstrates that the process during temperature range from 373 to 513 K was phase transformation. Photographs of polarizing microscope confirmed the conclusion. The decomposition of cattlehide collagen fibers starts at about 523 K. The cattlehide collagen fibers may undergo the process of melting, oxidation and decomposition. In decomposition, more than three steps take place. The mass spectra and Fourier transform infrared spectrometry stated clearly that double bond of carbon to oxygen, carbon to sulfur and carbon to nitrogen were destroyed firstly because the carbon dioxide, carbon monoxide and ammonia evolved simultaneously. The second peak of carbon monoxide in mass spectra indicated that some organic fragments were decomposed above 1073 K which confirmed that thermal degradation of leather is more than three steps.     

Using TG–FTIR and TG–MS to study thermal degradation of metal hypophosphites

Three typical metal hypophosphite flame retardants La(H₂PO₂)₃·H₂O (LHP), Ce(H₂PO₂)₃·H₂O (CHP), and Al(H₂PO₂)₃ (AHP) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis (TG), derivative thermogravimetric analysis, and differential thermal analysis. The thermal degradation products from the synthesized metal hypophosphites were also investigated using thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR) and thermogravimetry coupled with mass spectrometry (TG–MS). The synthesized metal hypophosphites were also used as flame retardants for poly (1,4-butylene terephthalate) (PBT), and the combustion properties of flame-retarded PBT were evaluated using the limiting oxygen index and UL-94 tests. The results showed that the metal hypophosphites LHP, CHP, and AHP can be used as effective flame retardants for PBT, and these compounds can be obtained through a simple precipitation method. TG–FTIR and TG–MS results showed that the degradation process of AHP involves two steps, corresponding to the removal PH₃ reaction and the further dehydration reaction of the hydrogen phosphate aluminum. While LHP and CHP have three degradation steps, the additional step is due to that LHP and CHP which will loss the crystal water at lower temperature.     

Compositional analysis of UV-cured acrylic ester resins by pyrolysis–gas chromatography in the presence of organic alkali

Compositional analysis of UV-cured resins consisting of multi-component acrylic esters was studied by pyrolysis–gas chromatography (Py–GC) in the presence of organic alkali, tetramethylammonium hydroxide (TMAH). The pyrograms of the UV-cured resins formed from ethylene oxide modified bisphenol A diacrylate (EBADA) contained specific products such as methyl acrylate (MA) and various dimethyl ethers of ethylene oxide modified bisphenol A reflecting the numbers of ethylene oxide units in the original EBADA. Meanwhile the pyrograms of the UV-cured resins comprised of acrylated polyfunctional aliphatic alcohols such as pentaerythritol triacrylate (PETA) and dipentaerythritol hexacrylate (DPEHA) contained methyl ethers reflecting the structure of the original alcohols. In addition, considerable amounts of pyrolyzates with non-methylated hydroxyl groups were also detected for aliphatic alcohol moieties. The compositions of the UV-cured resins containing multi-component acrylic esters were also analyzed based on the relative yields of the characteristic pyrolyzates of each acrylic ester. For calibration purpose, a series of UV-cured standard samples, which contained known amounts of the individual acrylic ester and neopentylglycol diacrylate (NPGDA) used as an internal standard, were measured. The compositions of the multi-component UV-cured resins determined using this approach showed good agreement with the theoretical values estimated from the feed composition.     

Study on the effects of flame retardants on the thermal decomposition of wood by TG–MS

The effect of three flame retardants, K₂CO₃, Na₂SiO₃·9H₂O, and Na₂B₄O₇·10H₂O on the process and composition of volatile products of the thermal degradation of wood has been investigated by the thermogravimetric (TG), differential thermogravimetry (DTG), differential thermal analysis (DTA), and the synchronous thermogravimetry–mass spectrometry (TG–MS) analysis methods. The results showed that the ion current intensity and ion peak area of m/z = 18 and 44 MS signals were increased by the flame retardants but the ion peak area of m/z = 28 MS signal was decreased (except K₂CO₃) at the meantime. What’s more, the ion current intensity and ion peak area of m/z = 60 and 68 MS signals were also decreased (except K₂CO₃), which mean that Na₂B₄O₇ can significantly enhances the dehydration and inhibits the depolymerization of wood. Although K₂CO₃ accelerates the dehydration reaction, it cannot inhibit the depolymerization reaction effectively, so the flame retardant efficiency of K₂CO₃ is decreased with the higher concentration. The catalysis of dehydration reaction of Na₂SiO₃ is the worst one.     

Application of off-line pyrolysis with dynamic solid-phase microextraction to the GC–MS analysis of biomass pyrolysis products

Pyrolysis coupled with dynamic solid-phase micro extraction (Py-SPME) followed by GC–MS analysis was applied to the determination of volatile compounds evolved by a micro-scale off-line pyrolysis apparatus, in order to extend the information affordable with this type of analytical equipment. The Py-SPME method with a carboxen/PDMS fiber working in the retracted mode was tested on four biomass samples (switchgrass, sweet sorghum, corn stalk and poplar) for qualitative analysis of semi-volatile pyrolysis products and quantitative determination of main volatiles (C₁–C₄) pyrolysis products. The developed procedure allowed capturing and analysis of all GC analyzable compounds, without memory effects and with good peak resolution also for early GC-eluting compounds. Twelve main volatile pyrolysis products, including hydroxyacetaldehyde and acetic acid, were successfully quantified; in spite of the intrinsic variability introduced by dynamic SPME sampling, results were relatively accurate and consistent with literature data on bench pyrolysis reactors.     

Activation energy in the thermal decomposition of MgH2 powders by coupled TG–MS measurements

The thermal desorption of hydrogen from commercial MgH₂ powders was investigated by coupled thermogravimetry and mass spectroscopy (TG–MS). The analysis of the evolved gas species gives a detailed picture of the composition of the initial specimen and of its thermal decomposition: just before the H₂ release from MgH₂, additional H₂O and CO₂ are detected, sensing the presence of MgCO₃ and Mg(OH)₂ in the initial specimen. Measurements done at different heating rates allowed the determination of apparent activation energies for the whole thermal process. Moreover, by considering appropriate ion current signals of the MS data, the activation energies of the single chemical reactions, leading to the formation of H₂O, CO₂, and H₂, were obtained. Differences coming from the choice of the (model-free isoconversion) method of analysis (Kissinger–Akahira–Sunose; Flynn–Wall–Ozawa; Starink; Friedman equations) are evidenced and discussed.     

Determination of Pitavastatin in Human Plasma by LC–MS–MS

A simple and rapid LC–MS–MS assay was developed and validated for the quantitative determination of pitavastatin in human plasma. Sample pretreatment involved simple protein precipitation by addition of acetonitrile. Separation was on an Agilent 1.8 μm Zorbax SB-C18 column (150 mm × 4.6 mm) at 25 °C using isocratic elution with methanol–0.1% formic acid in water (85:15, v/v) at a flow rate of 0.4 mL min^?1. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring mode by monitoring the ion transitions m/z 422.0 → 290.1 for pitavastatin, and m/z 330.1 → 192.1 for paroxetine (IS). LC–MS–MS was found to improve the quantitation of pitavastatin in plasma and was successfully applied in pharmacokinetic studies.     

Analysis of Nanafrocin in Foodstuffs of Animal Origin by LC–MS–MS

A new, rapid, and efficient method, multiple reaction monitoring liquid chromatography–tandem mass spectrometry, has been developed for analysis of nanafrocin in foodstuffs of animal origin. The researchers used a C₁₈ stationary phase coupled with triple-quadrupole tandem mass spectrometry in negative-electrospray mode. The limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.01 mg kg^?1, respectively, in the matrixes. Detector response was found to be a linear function of concentration over the range 0.005–0.1 mg kg^?1 in each matrix. Mean overall recovery (n = 10) of nanafrocin varied from 71 to 101%. The results show that identification and quantification of nanafrocin residues in foodstuffs of animal origin can be successfully achieved by use of the proposed LC–MS–MS method.     

Synthesis of submicrometer zirconium carbide formed from inorganic–organic hybrid precursor pyrolysis

Zirconium carbide (ZrC) was synthesized from inorganic–organic hybrid precursor’s pyrolysis by solution-based processing. Zirconium-containing complexes, which were obtained by chelation of oxide bidentate ligands to zirconium, were used to combine with phenolic resin to form precursors for ZrC. The precursors using specific ligands including acetylacetone, ethyleneglycol, and salicylic acid transformed into pure ZrC at a relatively low temperature (1,550 °C) in addition to that using lactic acid. As a comparison, synthesis of ZrC only using zirconium oxychloride octahydrate (ZrOCl₂·8H₂O) and phenolic resin was also conducted. The synthesized powders had a small average crystallite size (~300 nm), and a low oxygen content (~2.5 at.%). The conversions from as-synthesized preceramic precursors to ceramics were studied by means of FTIR, SEM, EDS, XRD, and XPS. The oxidation behavior of the synthesized ZrC in air was studied by DSC-TG analysis.     

Quantification of phytochelatins in plants by reversed-phase HPLC–ESI–MS–MS

An on-line HPLC–ESI–MS–MS method has been developed for determination of glutathione and phytochelatins (PC) in plant tissues. For sample pretreatment, dithiothreitol (DTT) must be added at the very beginning, as an anti-oxidant. Optimization of instrumental conditions i.e. composition of HPLC mobile phase, ionization efficiency of the electrospray interface, and MS–MS detection in the multiple ion-monitoring mode, are the central aspects of this work. A polystyrene-packed column was found to be superior to a standard silica-packed reversed-phase column. A concave quadratic gradient of ammonium formate buffer and acetonitrile was found to be optimum. The limits of quantitation were 0.2 mol kg^–1 plant tissue for glutathione and PC. The method has been applied to analysis of tissue samples from Vicia faba grown in Cd-containing nutrient solutions.Dedicated to the memory of Wilhelm Fresenius     

Characterisation of permanent markers by pyrolysis gas chromatography–mass spectrometry

Pyrolysis gas chromatography–mass spectrometry (PyGC-MS) was used as a rapid method for the characterization of permanent marker ink. Twenty-four samples of various colours purchased from different manufacturers were characterised. Four main typologies of polymer-binding medium could be distinguished on the basis of the pyrolysis products, and differentiation between permanent markers of different manufacturers could be accomplished. For some permanent marker samples, PyGC-MS analysis allowed pigment identification as well.     

Application of DSC–TG and NMR to study the soil organic matter

The environmental concern on soil exploitation, linked to global warming by the Kyoto protocol, is responsible for increasing interest in the understanding of the role of the composition and structure of the soil organic matter (SOM) on soil carbon, C, dynamics. Thermal analysis and nuclear magnetic resonance (NMR) are applied to study the thermal properties, the structure and composition of the SOM of six samples with different C contents in order to improve the interpretation of results given by thermal analysis. Results showed that the direct integral of the combustion peaks obtained by DSC and the percentage of SOM given by TG were both directly related to the quantity of total soil C. Thus, soils with higher C content showed higher energy content too. The combustion temperatures of the curves given by DSC are those reported for labile OM. NMR results indicated the presence of aliphatic C, carbohydrates, and a weak signal in the aromatic C band in all the samples that was not detected in the DSC curves. Only two samples showed carboxyl/carbonyl C which was not detected by DSC also.