Evolved gas analyzer

Figure 1. The Ferkin-Elmer laboratory for thermal analysis. From left to right the DSC-1B differential scanning calorimeter with evolved gas analyzer, the TGS-1 thermobalance (top to bottom), the recorder chart control, model UU-1 temperature programmer control, and model TMS-1 control unit. At right is the model TMS-1 thermomechanical analyzer.

The loss of CO2 equals a loss in weight of (22.0 mg/50.0 mg) x 100% = 44%. From the stoichiometry, it is expected that 1 mole of CO2 is lost for every mole of CaCOs present, which corresponds to a loss of 44% of the mass of 1 mole of CaCOs. The experimental mass loss supports the theoretical loss if the decomposition of CaCOs proceeds according to the reaction proposed. The formation of CO2 can be verified by having the evolved gas analyzed by MS or by online IR spectroscopy. The CaO can be confirmed by analysis of the residue by XRD or other techniques. 

Hoffman, J.H., Chaney, R.C.,Hammack,H. (2008) Phoenix mars mission—the Thermal Evolved Gas Analyzer. Journal of the American Society for Mass Spectrometry, 79(10), 1377-1383. 

Thermal Chromatography. The effect of heating rate on oil yields, composition and rate of formation was carried out with a commercial thermal chromatograph (Model MP-3 Chromalytics, Inc.). This instrument contains the following elements l) a temperature programmable pyrolyzer, 2) an evolved gas analyzer with both flame ionization (F.I.D) and thermal conductivity (T.C.) detectors,... 

The reaction processes of substances cannot be analyzed by simple DTA/DSC or TG when thermal transition and the mass change due to reaction overlap. If DTA/DSC or TG is coupled with an evolved gas detector (EGD) and/or evolved gas analyzer (EGA), the reaction process can clearly be detected. Among various thermal analysis coupled simultaneous techniques [56], DTA/DSC or TG coupled with EGD and/or EGA is extensively used. TA-EGD-EGA coupled... 

In this IR sampling technique, a thermogravimetric (TG) analyzer is interfaced to an IR spectrophotometer so that the evolved gas from the sample/TG furnace is directed to an IR gas cell. This IR sampling technique lends itself to the identification and quantitation of residual solvent content for a pharmaceutical solid [17], and also to the investigation of pharmaceutical pseudopolymorphs. 

The ability of the new precursors to decompose thermally to yield singlephase CIS was investigated by powder XRD analysis and EDS on the nonvolatile solids from the TGA experiments of selected compounds. Furthermore, using TGA-evolved gas analysis (EGA), the volatile components from the degradation of the SSPs could be analyzed via real-time fourier transform infrared (FTIR) and mass spectrometry (MS), thus providing information for the decomposition mechanism.3 The real-time FTIR spectrum for 7 and 8 shows absorptions at approximately 3000,1460,1390,1300, and 1250 cm-1 (see Fig. 6.7). 

Elemental composition Ba 69.58%, C 6.09%, O 24.32%. The compound is digested with nitric acid under heating and the solution is analyzed for barium by atomic absorption or emission spectrometry (see Barium). Carbon dioxide may be determined by treating a small amount of the solid with dilute HCl and analyzing the evolved gas by GC using a thermal conductivity detector or a mass spectrometer. The characteristic mass of CO2 is 44. 

Evolved gas analysis QEGA). Temperature programmed (5°C/min) mass spectrometrlc (MS) techniques were used to analyze the volatile products formed during sample heating. 

Evolved gas analysis Nature and composition of gas liberated during thermal analysis. Gas analyzer... 

COj/Oj in the Off-Gas CO2 evolution from a bioreactor is closely related to the physiological state and the activity of microorganisms in a bioreactor because CO, evolves as a result of catabolism and respiration by microorganisms or cells. Therefore, it is helpful to measure the content of CO2/O2 in the exhaust gas in order to understand the physiological climate of a bioreactor. The CO2 and O2 content in the exhaust gas are taken from the streamline and analyzed by infrared spectrophotometer (CO2) and galvanic cell probe (O,). The wet off-gas must be desiccated before being introduced into the gas analyzer. 

The main benefits of the mass chromatographic system can be summarized as follows. (1) Precise quantitative analysis can be performed without individual peak calibration. (2) Molecular weights are readily determined for compounds that can be gas chromatographed. (3) Peak identification is usually possible by the combined use of molecular weight and retention data (when such data are available). (4) The unique trap design and dual aspects of the instrument are ideally suited for evolved gas analysis from thermal analyzers, catalyst studies, etc. These benefits will be discussed throughout the paper with emphasis oriented to the polymer field. 

This instrument has evolved from ihe laboratory spectrophotometer to satisfy the specific needs of industrial process control. While dispersive instruments continue to be used in some applications, the workhorse infrared analyzers in process control are predominantly nondispersive infrared (NDIR) analyzers. The NDIR analyzer ean be used for either gas or liquid analysis. For simplicity, the following discussion addresses the NDIR gas analyzer, hut it should be recognized that the same measurement principle applies to liquids. The use of infrared as a gas analysis technique is certainly aided by the fact that molecules, such as nitrogen (N ) and oxygen tO , which consist of two like elements, do not absorb in the infrared spectrum. Since nitrogen and oxygen are the primary constituents of air. it is frequently possible to use air as a zero gas. 

The most recent generation of NDIR analyzers have evolved to satisfy the frequently harsh industrial environments encountered. These analyzers utilize solid-state sensors for the detection of infrared radialion. Most frequently used sensors are lead selenide (PhSc). thermopiles, or pyroelectric detectors. The gas analyzers generally are configured as single-path instruments, dual-beam with a reference palh. or dual-channel with a reference filter. 

The photoreactor has a flat quartz window 11 err in diameter. 50 mg of powder photocatalyst and 40 ml of Na2C03 aqueous solution are introduced in the pohotoreacto-. After solar lighl irradiation, the evolved gas was analyzed by GC after connecting the photoreactor to the glass closed gas-circulating system shown in Fig.14.1. 

Fig. 1 is a schematic diagram showing the procedures for the fractionation of products after the bark was treated with H2O2. The evolved gas was collected in a sample bag and then analyzed using gas chromatography (GC). The GC analysis was done using a WG-100 column (Shimadzu CC-8A), The temperatures of the oven, injector and detector were 50 C and TO C, respectively. The TCD current was 120 mA. The carrier gas was He at a flow rate of 33 mL min. ... 

The samples (10 mg for p3rridine and 20 mg for NH3) were placed in a U tube on a fritted glass. They were pretreated at 875 K for 6h imder an air flow and then 6h under vacuum at the same temperature in order to decompose the template. NH3 or pyridine were adsorbed at room temperature for Ih and the excess was evacuated for 6h at 385 K for NH3 and 425 K for pyridine. The thermodesorption was performed at a rate of 5 per min.. The gas evolved was analyzed by a quadrupole mass spectrometer Quadruvac PGA 100 Leybold-Heraeus. 

Photoreactions. A sample solution containing 0.33 mM [Ni-(bpy)3](Cl04)2 and 0.5 M triethylamine in MeCN (3.0 mL) w bubbled with CO2 for 20 min and then irradiated at 313 nm (100 W Hg-Xe arc lamp with 1/4 m monochromator) in a 1-cm quartz cuvette under stirring. After photolysis, 0.1 mL of air and 0.1 mL of water were added to decompose the CO adduct. The CO evolved was analyzed using a Varian gas chromatograph [Model 3700, He carrier gas, 5-A molecular sieve column (4-m length, 1/8-in. diameter)] equipped with a thermal conductivity detector. Each run was carried out two or three times. 

Not only did this illustrious pioneer develop a pyrometer and temperature scale, but he had also foreseen the development of the thermal analysis techniques of diJaiomeiry, thermogravimetry, and evolved gas analysis. Of most interest here is EGA in which he took one of the china clay pieces and heated it in a sealed vessel attached to a bladder. The contents of the bladder were then analyzed for any evolved gases. Unfortunately, water vapor was nol detected during the heating of the clay. 

Infrared spectroscopic techniques have long been used to analyze gas streams in industrial chemical processes. Recently, with the advent of fastscan infrared spectrometers, they have been used as gas chromatograph detectors. One requirement of their use, needless to say, is that the compound must possess one or more infrared absorption band. By means of a carrier gas. the evolved gas sample from a pyrolysis chamber can be readily passed through an infrared cell for analysis. Infrared systems that can be employed include (1) nondispersive analyzers, (2) dispersion spectrometers. 3) band-pass filter-type instruments, and (4) interference spectrometers all these techniques have been adequately reviewed by Low (87). 

The evolution of gas from a thermal analyzer such as a TGA, DTA, or DSC may be determined using evolved gas detection (EGD) or, if qualitative or quantitative analysis of the gas is required, evolved gas analysis (EGA). These techniques are essentially a combination of thermal analysis and MS, tandem mass spectrometry (MS-MS), GC-MS or other... 

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