Gas chromatography principles and instrumentation

Because the FPD responds to both aerosol and gaseous sulfur species, it has also been possible to modify these instruments to continuously measure aerosol sulfur by selectively removing gaseous sulfur compounds with a lead(II) oxide-glycerol coated denuder (55). Use of such an instrument for airborne measurements of aerosol sulfur in and around broken clouds has been reported (57). In principle, speciation between aerosol sulfate, disulfate, and sulfuric acid by selective thermal decomposition (58, 59) can also be achieved. Flame photometric detectors have also been used as selective detectors for gas chromatography. Thornton and Bandy (60) reported the use of a chromatographic system with a flame photometric detector for airborne measurement of S02 and OCS with a detection limit of 25 pptrv. 

HPLC had now become competitive with gas chromatography, the other major instrumental analytical separation technique of the time. HPLC was able to deal with a broader range of samples than gas chromatography (GQ, and had the advantage of simplified sample preparation in those cases that could be solved by either technique. In principle, anything that can be dissolved can be subjected to an HPLC analysis. Consequently the number of application areas of HPLC expanded rapidly. 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Atomic Fluorescence Spectrometry. Gas Chromatography Pyrolysis Mass Spectrometry. Liquid Chromatography Normal Phase Reversed Phase Size-Exclusion. Polarography Inorganic Applications Organic Applications. Polymers Synthetic. Thin-Layer Chromatography Overview. Voltammetry Organic Compounds. 

See also Air Analysis Outdoor Air. Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Environmental Analysis. Gas Chromatography Overview Principles Instrumentation. Liquid Chromatography Overview Principles Instrumentation. Personal Monitoring Active Passive. Quality Assurance Quality Control Instrument Calibration. Spectrophotometry Ovenriew Inorganic Compounds Organic Compounds. 

Schomburg G (1995) Two dimensional gas chromatography principles, instrumentation and methods. Journal of Chromatography A 703 309-325. 

See also Activation Anaiysis Neutron Activation. Atomic Emission Spectrometry Principies and Instrumentation. Bleaches and Sterilants. Chiroptical Analysis. Chromatography Principles. Conductimetry and Oscillometry. Coulometry. Fire Assay. Food and Nutritional Analysis Overview. Gas Chromatography Principles. Gravimetry. Indicators Redox. Infrared Spectroscopy Overview. Ion Exchange Oven/iew. Isotope Dilution Analysis. Lipids Fatty Acids. Liquid Chromatography Size-Exclusion. Radiochemical... 

See also Archaeometry and Antique Analysis Dating of Artifacts Metaiiic and Ceramic Objects. Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Mass Spectrometry Inductively Coupled Plasma. Gas Chromatography Mass Spectrometry. Mass Spectrometry Time-of-Flight Stable Isotope Ratio Clinical Applications Environmental Applications Food Applications Forensic Applications. 

See also Atomic Absorption Spectrometry Interferences and Background Correction. Atomic Emission Spectrometry Principles and Instrumentation Interferences and Background Correction Flame Photometry Inductively Coupled Plasma Microwave-Induced Plasma. Atomic Mass Spectrometry Inductively Coupled Plasma Laser Microprobe. Countercurrent Chromatography Solvent Extraction with a Helical Column. Derivatization of Analytes. Elemental Speciation Overview Practicalities and Instrumentation. Extraction Solvent Extraction Principles Solvent Extraction Multistage Countercurrent Distribution Microwave-Assisted Solvent Extraction Pressurized Fluid Extraction Solid-Phase Extraction Solid-Phase Microextraction. Gas Chromatography Ovenriew. Isotope Dilution Analysis. Liquid Chromatography Ovenriew. 

See also Atomic Absorption Spectrometry Principles and Instrumentation Fiame Eiectrothermai Vapor Generation. Atomic Emission Spectrometry Inductively Coupled Plasma. Gas Chromatography Environmental... 

Other combinations are available. For example, liquid chromatographs connected to mass spectrometers (known as liquid chromatography-mass spectrometry [LC-MS]) are fairly common. Almost any combination of two instruments that can be thought of has been built. In addition, two of the same instruments can be connected so that the output from one is fed directly into the other for further separation and analysis. Examples include two mass spectrometers in an MS-MS arrangement and two different gas chromatography columns connected in a series, known as GC-GC. To keep up with these advances, one needs to have a working knowledge of the fundamental principles involved in the techniques and of the abbreviations used for the various instrumentation methods. 

A standard arrangement for sampling gaseous products downstream of the reactor is shown in Fig. 5. In a needle valve (or a similar device), the reactor effluent is depressurized and the flow rate is controlled. In the vast majority of cases, the analytical instrument of the choice will be a gas chromatograph equipped with a capillary column, because such an instrument often allows a good separation of the products and, if equipped with an appropriate detector, a reliable quantitative analysis of these products. The working principle of gas chromatography, however, is inherently... 

This is chemically the same principle as for conventional LLE, but can be performed in a flow system, which permits easy automation and interfacing to analytical instruments. The technique is most easily interfaced to gas chromatography (GC) or to normal-phase high performance liquid chromatography (NP-HPLC), as the extract ends up in an organic phase. In principle, the membrane could also be hydrophilic, which would lead to an aqueous phase in the membrane pores. This seems not yet to have been tried for analytical purposes. 

Miniaturization is especially advantageous in an era when compounds with extraordinarily interesting structural and thermochemical properties are being synthesized but only in very small amounts. Because the first principle of all calorimetry is that the sample must be well defined and pure (or at least have a small amount of known impurity), microcalorimetry permits use of a wider range of contemporary purification techniques, especially preparative gas chromatography, than traditional calorimetry. There is, of course, no reason to suppose that the evolutionary process of hydrogen calorimeter design cannot be continued to produce smaller, safer, and possibly more accurate instruments. 

GC-MS systems used to fill a room and cost several hundred thousand dollars. Today, relatively inexpensive compact benchtop systems are available and widely used in laboratories. A modem GC-MS instrument is shown in Figure 20.8. We describe first the principles of mass spectrometers and types of instruments, and then discuss how the two techniques of gas chromatography and mass spectrometry are used together. 

Mass spectrometry detection in liquid chromatography, like with gas chromatography, has become a powerful analysis tool for sensitive and selective mass detection in characterizing complex samples. Review the principles of mass spectrometry and the types of instruments used for chromatography detection in Chapter 20. 

The measurement of concentration presents a vast, active and challenging field of instrumental techniques of chemical analysis. This is the field whose development has the largest impact on kinetic studies. In principle there are two types of methods of analysis batch and continuous. As a familiar example of a batch analysis we can take standard gas chromatography, where discrete samples are analyzed and require a fairly long time for an analysis to be completed. On the other extreme are methods involving electrodes and other probes that output an analogue signal that varies continuously with composition. 

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