Spectroscopy/spectrometry detectors

In contrast to IR and NMR spectroscopy, the principle of mass spectrometry (MS) is based on decomposition and reactions of organic molecules on theii way from the ion source to the detector. Consequently, structure-MS correlation is basically a matter of relating reactions to the signals in a mass spectrum. The chemical structure information contained in mass spectra is difficult to extract because of the complicated relationships between MS data and chemical structures. The aim of spectra evaluation can be either the identification of a compound or the interpretation of spectral data in order to elucidate the chemical structure [78-80],... 

Coupling of analytical techniques (detectors) to high-performance liquid chromatographic (HPLC) systems has increased in the last tree decades. Initially, gas chromatography was coupled to mass spectrometry (MS), then to infrai ed (IR) spectroscopy. Following the main interest was to hyphenate analytical techniques to HPLC. 

Detection in SFC can be achieved in the condensed phase using optical detectors similar to those used in liquid chromatography or in the gas phase using detectors similar to those used in gas chromatography. Spectroscopic detectors, such as mass spectrometry and Fourier transform infrared spectroscopy, are relatively easily interfaced to SFC compared to the problems observed with liquid mobile phases (see Chapter 9). The range of available detectors for SFC is considered one of its strengths. 

Energy-dispersive spectrometry (EDS) is a technique of X-ray spectroscopy that is based on the simultaneous collection and energy dispersion of characteristic X-rays. Typical ED detectors are thermoelectrically cooled semiconductors (usually operated at 77 K), PIN diodes,... 

Auger electron spectroscopy Phosphorous/nitrogen-selective alkali/flame ionisation detector Atomic force microscopy Atomic fluorescence spectrometry All-glass heated inlet system... 

Secondary Ion Mass Spectrometry Basic Concepts, Instrumental Aspects, Applications and Trends. By A. Benninghoven, F. G. Ruenauer, and H.W.Werner Analytical Applications of Lasers. Edited by Edward H. Piepmeier Applied Geochemical Analysis. By C. O. Ingamells and F. F. Pitard Detectors for Liquid Chromatography. Edited by Edward S.Yeung Inductively Coupled Plasma Emission Spectroscopy Part 1 Methodology, Instrumentation, and Performance Part II Applications and Fundamentals. Edited by J. M. Boumans... 

Non-specific sum parameter analysis [12,13], which is still used today, failed [14,15] in the analyses of some of these compounds. Chromatographic methods in combination with non-substance specific detectors, e.g. colorimetric and photometric [5] or with substance specific detectors such as IR (infrared spectroscopy), NMR (nuclear magnetic resonance spectroscopy) or MS (mass spectrometry), are applied increasingly nowadays. 

Other methods for the determination of aromatics in naphtha include a method (ASTM D5580) using a flame ionization detector and methods that use combinations of gas chromatography and Fourier transform infrared spectroscopy (GC-FTIR) (ASTM D5986) and gas chromatography and mass spectrometry (GC-MS) (ASTM D5769). 

Laprade, B.N. Labich, R.J. MicroChannel Plate-Based Detectors in Mass Spectrometry. Spectroscopy 1994,9,26-30. 

Figure 1.2 shows the basic instrumentation for atomic mass spectrometry. The component where the ions are produced and sampled from is the ion source. Unlike optical spectroscopy, the ion sampling interface is in intimate contact with the ion source because the ions must be extracted into the vacuum conditions of the mass spectrometer. The ions are separated with respect to mass by the mass analyser, usually a quadrupole, and literally counted by means of an electron multiplier detector. The ion signal for each... 

Eluate from a chromatography column can be passed through a plasma to atomize and ionize its components and measure selected elements by atomic emission spectroscopy or mass spectrometry. An atomic emission detector directs eluate through a helium plasma in a microwave cavity. Every element of the periodic table produces characteristic emission that can be detected by a photodiode array polychromator (Figure 20-14). Sensitivity for sulfur can be 10 times better than the sensitivity of a flame photometric detector. 

HPLC-UV-NMR can now be considered to be a routine analytical technique for pharmaceutical mixture analysis and for many studies in the biomedical field. HPLC-UV-NMR-MS is becoming more routine with a considerable number of systems now installed worldwide, but the chromatographic solvent systems are limited to those compatible with both NMR spectroscopy and mass spectrometry. The increased use of HPLC-UV-IR-NMR-MS is possible, but it is unlikely to become widespread, and the solvent problems are more complex. The future holds the promise of new technical advances to improve efficiency, and to enhance routine operation. These approaches include the use of small-scale separations, such as capillary electrochromatography, greater automation, and higher sensitivity and lower NMR detection limits through the use of NMR detectors cooled to cryogenic temperatures. 

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