Thermogravimetric instruments

Thermogravimetric instrumentation should include several basic components in order to provide the flexibility necessary for the production of useful analytical data. These components are (a) a balance (b) a heating device (c) a unit for temperature measurement and control (d) a means for automatically recording the mass and temperature changes and (e) a system to control the atmosphere around the sample. 

Control of the Atmosphere. The composition of the atmosphere surrounding the sample can have large and (if properly used) advantageous effects. For that reason, most thermogravimetric instruments provide some means of altering this atmosphere in most cases, a static or flowing atmosphere of any desired composition can be provided. In addition, thermogravimetric determinations can be done in a vacuum (many systems can achieve pressures of 10 torr or less), or at elevated pressures. 

A list of suppliers of commercial thermogravimetric instruments is given in Table 3.3 below. 

Other thermogravimetric instruments are produced by many of the manufacturers listed in Ref. 18, Chapter 5. Particularly well known are those of Netzsch, Perkin-Elmer, Setaram, and PL Thermal Sciences. For detailed information and updates, one should get the latest instrument descriptions from the manufacturers. 

Mixtures can be identified with the help of computer software that subtracts the spectra of pure compounds from that of the sample. For complex mixtures, fractionation may be needed as part of the analysis. Commercial instmments are available that combine ftir, as a detector, with a separation technique such as gas chromatography (gc), high performance Hquid chromatography (hplc), or supercritical fluid chromatography (96,97). Instmments such as gc/ftir are often termed hyphenated instmments (98). Pyrolyzer (99) and thermogravimetric analysis (tga) instmmentation can also be combined with ftir for monitoring pyrolysis and oxidation processes (100) (see Analytical methods, hyphenated instruments). 

Nitrogen adsorption was performed at -196 °C in a Micromeritics ASAP 2010 volumetric instrument. The samples were outgassed at 80 °C prior to the adsorption measurement until a 3.10 3 Torr static vacuum was reached. The surface area was calculated by the Brunauer-Emmett-Teller (BET) method. Micropore volume and external surface area were evaluated by the alpha-S method using a standard isotherm measured on Aerosil 200 fumed silica [8]. Powder X-ray diffraction (XRD) patterns of samples dried at 80 °C were collected at room temperature on a Broker AXS D-8 diffractometer with Cu Ka radiation. Thermogravimetric analysis was carried out in air flow with heating rate 10 °C min"1 up to 900 °C in a Netzsch TG 209 C thermal balance. SEM micrographs were recorded on a Hitachi S4500 microscope. 

TA instruments has developed automated thermogravimetric analysis and related kinetic programs that enable a rapid determination of decomposition rates to be made. The following excerpt from a TA application brief [57] explains the method ... 

The essential requirements for an instrument (Figure 11.1) meant for thermogravimetric analysis are, namely ... 

Discuss, the fundamental theory of thermogravimetric analysis , and its instrumentation aspects in an elaborated manner. 

TG-FT-IR, Pyrolysis analyses were performed on the preliquefaction solids using thermogravimetric (TG) analysis with on-line analysis of the evolved products (including an infrared spectrum of the condensables) by FT-IR. The TG-FTIR method has been described previously (23-25). The Bomem TG/plus instrument was employed. A sample is continuously weighed while it is heated. A flow of helium sweeps the products into a multi-pass cell for FT-IR analysis. Quantitative analysis of up to 20 gas species is performed on line. Quantitation of the tar species is performed by comparison with the balance reading. 

Major instrumentation involved with the generation of thermal property behavior of materials includes thermogravimetric analysis (TG, TGA), DSC, differential thermal analysis (DTA), torsional braid analysis (TBA), thermomechanical analysis (TMA), thermogravimetric-mass spectrometry (TG-MS) analysis, and pyrolysis gas chromatography (PGQ. Most of these analysis techniques measure the polymer response as a function of time, atmosphere, and temperature. 

Elemental composition Zn 63.24%, F 36.76%. ZnF2 may be characterized from its x-ray and other physical properties. The water of crystaUization in the tetrahydrate may be determined by thermogravimetric method. A small amount of compound is dissolved in water (anhydrous salt is very slightly soluble in water) and analyzed for fluoride ion by the electrode method or by ion chromatography. A diluted acid solution of the compound is analyzed for zinc by various instrumental methods (See Zinc). 

The section Analysis starts with elemental composition of the compound. Thus the composition of any compound can be determined from its elemental analysis, particularly the metal content. For practically all metal salts, atomic absorption and emission spectrophotometric methods are favored in this text for measuring metal content. Also, some other instrumental techniques such as x-ray fluorescence, x-ray diffraction, and neutron activation analyses are suggested. Many refractory substances and also a number of salts can be characterized nondestructively by x-ray methods. Anions can be measured in aqueous solutions by ion chromatography, ion-selective electrodes, titration, and colorimetric reactions. Water of crystallization can be measured by simple gravimetry or thermogravimetric analysis. 

The fresh and spent catalysts were characterized with the physisorption/chemisorption instrument Sorptometer 1900 (Carlo Erba instruments) in order to detect loss of surface area and pore volume. The specific surface area was calculated based on Dubinin-Radushkevich equation. Furthermore thermogravimetric analysis (TGA) of the fresh and used catalysts were performed with a Mettler Toledo TGA/SDTA 851e instrument in synthetic air. The mean particle size and the metal dispersion was measured with a Malvern 2600 particle size analyzer and Autochem 2910 apparatus (by a CO chemisorption technique), respectively. 

A differential scanning calorimeter (DSC), Dupont Instrument, Model DSC2910, was used to determine the glass transition temperatures. Thermo-gravimetric analyses were carried on a thermogravimetric analyzer (TGA), TA Instruments, Model Hi-Res TGA 2950. 

Thermal Analysis. The water contents of CPA and zeolite were measured by thermogravimetric analysis (TGA). Differential thermal analyses (DTA) were done for comparison. The instrument used was a Du Pont 900 with a TGA attachment. 

TG analysis of pantoprazole sodium was conducted obtained using a TA Instruments model 951 thermogravimetric analyzer system, calibrated using indium. The thermograms were carried out at a heating rate of 10°C/min, the sample size used ranged 5 to 10 mg, and the samples were heated over a temperature range of 50°C to 400°C. 

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