Thermal Analysis as Part of the Quality System within Industrial Laboratories

The use of thermal analysis as part of a quality system in industry can be effective only if the techniques are made to conform to high standards of quality assurance. Achieving these high standards is not problem free and there remain many issues which require the attention of thermal analysts in industry and academe. Fundamental aspects which have been considered include limitations due to instrument design, problems in computerised control and analysis. A key aim is towards validation of data at international level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal behaviour of urea-formaldehyde resins during curing

Urea-formaldehyde (UF) resins are the most widely used polycondensation resins today in manufacturing particleboards. The performance of UF resins in their processing is greatly influenced by curing characteristics. The cure process has been monitored by TG-DTA technique on a Setaram labsysTM instrument in dynamic heating conditions at different heating rates. Commercial UF resins from different suppliers used in Estonian particleboard factories were selected for TG-DTA measurements. Experiments were carried out without and with catalysts. Ammonium chloride and ammonium sulphate were used. Curing characteristics were evaluated both for fresh and aged resins. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal conductivity and thermal diffusivity of poly(acrylic acid) by transient hot wire technique

The paper describes a new transient hot wire instrument which employs 25.4 μm diameter tantalum wire with an insulating tantalum pentoxide coating. This hot-wire cell with a thin insulating layer is suitable for measurement of the thermal conductivity and the thermal diffusivity of electrically conducting and polar liquids. This instrument has been used for experimental measurement of the thermal conductivity and the thermal diffusivity of poly(acrylic acid) solution (50 mass%) in the temperature range of 299 to 368 K at atmospheric pressure. The thermal conductivity data is estimated to be accurate within ±4%. Thermal diffusivity measurements have a much higher uncertainty (±30%) and need further refinement.     

激光热透镜光谱分析法*

激光热透镜光谱法是20世纪80年代发展起来的一种光热光谱分析技术。该法以其高灵敏度、低检出限以及适应于微、少量样品分析等特点引 分析工作者的极大兴趣。本文从测量装置、理论、痕量无机物和有机物测定以及与其它分析技术的联用等方面对1990年以来激光热透镜光谱分析法的进展作了较为详细的综述。     

New Adventures in Thermal Analysis

This paper describes recent advances in thermal analysis instrumentation which combine the high resolution imaging capabilities of the atomic force microscope with physical characterisation by thermal analysis. Images of the surface may be obtained according to the specimen's thermal conductivity and thermal expansivity differences in addition to the usual topographic relief. Localised equivalents of modulated temperature differential scanning calorimetry, thermomechanical and dynamic mechanical analysis have been developed with a spatial resolution of a few micrometres. A form of localised thermogravimetry-evolved gas analysis has also been demonstrated. The same instrument configuration can be adapted to allow IR microspectrometry at a resolution better than the optical diffraction limit. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal conductivity of neon in the temperature range 400–2400K

Accurate measurements of the thermal conductivity of neon are given in the temperature range 400–2400K as obtained on an improved thermal conductivity column instrument. These data are found to be in good agreement with the earlier measurements of thermal conductivity from this laboratory and also with the available viscosity values. The present conductivity data are also compared with the predictions of kinetic theory in conjunction with several different forms for the intermolecular potential.     

Thermal degradation of ethylene (vinyl acetate)

Ethylene (vinyl acetate), EVA, is a copolymer which is thermally degraded at high temperatures, with acetic acid release at approximately 620 K. This release can be studied by using thermal methods, and in particular thermogravimetric analysis.The present work was focused on establishing the polymer weight loss with temperature in order to calculate the activation energy of the overall deacetylation process. To obtain the final results, a Mettler TC50 instrument coupled with a Mettler TC11 microprocessor was used.The activation energies of four different industrial EVA formulations were calculated. The results obtained by applying different kinetic methods reported in the literature agreed reasonably well; they were compared in order to select the best method of reporting EVA deacetylation results.The authors wish to express their appreciation to DGICYT (Spain), Project AMB 94-107, for financial support of this study.     

Thermal desorption comprehensive two-dimensional gas chromatography for in-situ measurements of organic aerosols

The complexity of organic composition and temporal variability of atmospheric aerosols presents an extreme analytical challenge. Comprehensive two-dimensional gas chromatography (GC x GC) has been used on time integrated filter samples to reveal the presence of thousands of individual organic compounds in aerosols, but without defining the temporal variability in composition ideal for providing information on source resolution and human exposure to specific pollutants. We hereby introduce a new instrument, 2D-TAG, which combines our in-situ thermal desorption aerosol GC (TAG) instrument with GC x GC allowing for dramatically improved separation of organics with automated measurements at hourly timescales.     

Thermal conductivity instrument for measuring planetary atmospheric properties and data analysis technique

This paper outlines the method of measurement and analysis of the thermal conductivity instrument (THP) that has successfully returned measurements from the atmosphere of Saturn’s moon Titan during the descent of the Huygens probe on 14^th January 2005. The technique is validated by analysing laboratory calibration data gathered by our instrument in three pure gases (nitrogen, methane, and ethane) over Titan’s temperature range (90 to 180 K). Calibration results show errors <1% compared to reference values when processed using this method.     

一次热解吸直接进样浓缩方法的研究--室内大气中挥发性有机化合物的分析

研制了新型的一次热解吸直接进样热解析仪．考察了新型热解吸仪热解吸定量的重复性、准确性、热解析率、线性等性能．通过实际采样分析证明,该方法提高了浓缩倍数,操作简单,易于掌握,定量重复性好、准确度高,分析结果可靠．适合大批量样品的分析测试．     

Thermal energy distribution observed in electrospray ionization

A new method was developed which fits a thermal internal energy distribution to ions formed by electrospray ionization. The molecular ion survival yield was measured and determined by RRKM calculations as a function of temperature. The ('characteristic') temperature was determined when the calculated and measured molecular ion survival yields were equal. The 'characteristic' temperatures were very similar (average RSD errors were 8%) for a set of analogous compounds (benzylpyridine salts), and the resulting thermal internal energy distributions were close to those determined by De Pauw's method. The validity of the method was also checked performing blackbody infrared radiation and on-resonance excitation experiments on a Fourier transform ion cyclotron resonance instrument with benzylpyridine salts and leucine enkephalin. The results strongly suggest that internal energy distributions in electrospray ionization are very close to thermal distributions. It was found that the characteristic temperature increases linearly with the cone voltage. It is suggested that the characteristic temperature can be used as a quantitative measure to control and standardize conditions in electrospray ionization. Copyright 1999 John Wiley & Sons, Ltd.     

Thermal and Structural Behavior of Milk Fat

The thermal and structural properties of unstable varieties of triacylglycerols (TGs) crystallizing in milk fat globules of cream are examined in the range -8- +50 degrees C using a new instrument allowing simultaneously time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC). Small angle X-ray diffraction shows that the unstable alpha form first formed by cream quenching to -8 degrees C corresponds in fact to two different lamellar phases corresponding to 2L (47 ?) and 3L (70.4 ?) arrangements of TGs. The bilayered structure is very unstable since it disappears during the course of a 20-min isothermal conditioning at -8 degrees C. On fast heating, the crystalline evolution of cream TGs demonstrates the monotropic character of their polymorphism. The structural and thermal behaviors of cream which are compared to that of its anhydrous milk fat isolated from the cream (C. Lopez et al., J. Dairy Sci., submitted) show that the crystallization occurring in emulsion droplets is similar to bulk. However, the comparison of XRD peak widths indicates that the TG crystallization is more disordered in emulsion. This disorder is attributed to the constraints due to the interface curvature in emulsion droplets. Copyright 2000 Academic Press.     

Field Measurement of NO2 and RNO2 by Two-Channel Thermal Dissociation Cavity Ring Down Spectrometer

A two-channel thermal dissociation cavity ring down spectroscopy (CRDS) instrument has been built for in situ, real-time measurement of NO₂ and total RNO₂ (peroxy nitrates and alkyl nitrates) in ambient air, with a NO₂ detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence (Mo-CL) instrument was also used for comparison. The average RNO₂ concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO₂ concentration by a bias of +1.69 ppbv in average, for the reason that it cannot distinguish RNO₂ from NO₂. The relative bias could be over 100% during the afternoon hours when NO₂ was low but RNO₂ was high.     

3-取代甲撑肼基二硫代甲酸甲酯类化合物热裂解的研究

首次采用气质联用仪研究了3-取代甲撑肼基二硫代甲酸甲酯类化合物的热裂解反应, 发现其在气化室可热裂解产生芳香腈、甲硫醇和异硫氰酸. 考察了3-苯基甲撑肼基二硫代甲酸甲酯在不同温度时的热裂解效率, 发现温度对其热裂解具有重要的影响, 该化合物在230 ℃时就能基本完全裂解. 同时还考察了含有不同取代基的化合物在210 ℃下的热裂解情况, 结果表明含推电子基的化合物比吸电子基化合物在气化室中裂解得完全, 热稳定性更差, 并根据实验结果推测了热裂解反应的可能机理.     

The ExoMars Raman spectrometer and the identification of biogeological spectroscopic signatures using a flight-like prototype

The molecular specificity of Raman spectroscopy provides a powerful tool for the analytical interrogation of mineralogical and many biological specimens. The Raman Laser Spectrometer (RLS) is a compact Raman spectrometer under development for deployment on the Martian surface as part of the forthcoming ESA ExoMars mission. This will be the first Raman instrument deployed in space. The scientific interpretation of the data emerging from such an instrument not only addresses the geological and mineral composition of the specimens but also enables an assessment to be made of organic biomaterials that may be preserved in the planetary geological record. The latter evidence centres on the residual and distinctive chemistry relating to the biological adaptation of the geological matrix that has occurred as a result of extremophilic organisms colonizing suitable geological niches for their survival in environmentally stressed habitats on Mars. These biogeological modifications have been studied terrestrially for Mars analogue sites and consist of both a geological component and residual key organic biomarkers, the recognition of which would be a prime factor in life detection surveys of a planetary surface and subsurface. In this paper, the protocols required for the Raman spectral discrimination of key biogeological features that may be detectable on the Martian planetary surface or subsurface are developed using the UK breadboard (UKBB) instrument. This instrument has been constructed to be functionally equivalent to the RLS flight instrument design in order to evaluate the feasible science return of the instrument which will finally be delivered to Mars. Initial Raman measurements using the UKBB are presented and compared with the performance of a commercial laboratory Raman microscope. The initial measurements reported here demonstrate this flight-like prototype achieves straightforward detection of biological signatures contained in geological matrices with Raman band signal to noise ratios high enough to determine sample composition by inspection and without the need for deconvolution or further processing.     

DSC测量中校正对热分析结果的影响

介绍了灵敏度及温度校正对基线和实验结果的影响.仪器温度和灵敏度校正可以减小差示扫描量热法(DSC)曲线的漂移,曲线上得到的温度和焓变值更接近理论值,减小了实验误差.所以,定期对仪器进行重新校正是必要的.     

Significant parameters in the optimization of MALDI-TOF-MS for synthetic polymers

One of the most significant issues in any analytical practice is optimization. Optimization and calibration are key factors in quantitation. In matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), instrument optimization is a limitation restricting quantitation. An understanding of the parameters that are most influential and the effects of these parameters on the mass spectrum is required for optimization. This understanding is especially important when characterizing synthetic polymers by MALDI-TOF-MS, due to the breadth of the polymer molecular mass distribution (MMD). Two considerations are important in quantitation, additivity of signal and signal-to-noise (S/N). In this study, the effects of several instrument parameters were studied using an orthogonal experimental design to understand effects on the signal-to-noise (S/N) of a polystyrene distribution. The instrument parameters examined included detector voltage, laser energy, delay time, extraction voltage, and lens voltage. Other parameters considered were polymer concentration and matrix. The results showed detector voltage and delay time were the most influential of the instrument parameters for polystyrene using all trans-retinoic acid (RA) as the matrix. These parameters, as well as laser energy, were most influential for the polystyrene with dithranol as the matrix.     

Thermal Analysis of the High-Energetic Material HNF

In a search for new storable high performance propellants for the European Space Agency (ESA), the solid oxidiser hydrazinium nitroformate (HNF) has been identified as a very promising ingredient for a new storable composite propellant. The purity and stability of HNF after production are very important indicators for the quality of HNF. In order to characterise HNF,many thermal analysis techniques as DSC and TG/DTA were performed to obtain more information about its stability and its (in)compatibility with other materials. Also some less familiar techniques such as the vacuum stability test and microcalorimetry have been performed. In relation to the safety, a relation between the friction and impact sensitivity and the physical-chemical properties is made. This revised version was published online in July 2006 with corrections to the Cover Date.     

Jet‐Cooled Thermal Modulator for Comprehensive Multidimensional Gas Chromatography

A jet of cool gas is used to locally cool a section of modulator tube in the presence of the stirred oven bath of a GC×GC instrument. Local cooling decouples the temperature of the modulator tube from that of the first dimension column, which was 100 meters long. Overall resolution of the GC×GC experiment was improved as a result. Another consequence of the jet‐cooled thermal modulation structure is the elimination of moving parts in the GC oven. By pulsing cold and hot jets of gas onto a modulator tube with solenoid valves, two stage thermal modulation can be obtained without the complexity of moving parts in the vicinity of the capillary columns.     

Use of a novel array detector for the direct analysis of solid samples by laser ablation inductively coupled plasma sector-field mass spectrometry

The use of laser ablation (LA) as a sample-introduction method for inductively coupled plasma mass spectrometry (ICP-MS) creates a powerful tool for trace elemental analysis. With this type of instrument, high analyte spatial resolution is possible in three dimensions with ng/g limits of detection and minimal sample consumption. Here, simultaneous detection is used to eliminate the correlated noise that plagues the ablation process. This benefit allows analyses to be performed with single laser pulses, resulting in improved depth resolution, even less sample consumption, and improved measurement precision. The new instrument includes an LA sample-introduction system coupled to an ICP ionization source and a Mattauch-Herzog mass spectrograph (MHMS) fitted with a novel array detector. With this instrument, absolute limits of detection are in the tens to hundreds of fg regime and isotope-ratio precision is better than 0.02% RSD with a one-hour integration period. Finally, depth-profile analysis has been performed with a depth resolution of 5 nm per ablation event.