Detectors atomic spectroscopy

AED Atomic emission detector Atomic emission spectroscopy... 

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

A number of organometallic compounds show promise for LCEC study, and a few have already been examined in detail (especially mercury alkyls) [9]. More highly conjugated organic compounds such as a,a-unsaturated ketones and imines are occasionally good candidates, but at this time UV detectors frequently outperform electrochemical detectors for such systems. At this writing there have been only a few reported LCEC studies of metal ions or metal complexes. Perhaps the major reason for this is that very little modern LC has been carried out on them using any detector. It is difficult to compete with atomic spectroscopy techniques for the determination of most elements, but as speciation becomes more important, it seems likely that more LCEC methods will be developed for metal complexes. 

Image Devices. Although he never assembled an actual TV-spectrometer, Margoshes was the first to recognize the potential of TV-type detectors in analytical atomic spectroscopy. In a series of reports (50,51,52) he speculated on the advantages of using an SEC tube [vide infra] to detect radiation dispersed by an echelle spectrograph. These reports and the recent availability of various solid-state array detectors have prompted numerous... 

While these data show that the image dissector is superior to the silicon target vidicon in several respects for atomic spectroscopy, the silicon vidicon and other integrating detectors retain significant advantages for molecular absorption (39) and fluorescence spectroscopy (40) where resolution requirements are not so demanding, available radiant fluxes are higher, and a... 

Felkel, H. L., Jr., "Evaluation of imaging detector coupled to an echelle grating spectrometer for atomic spectroscopy", Ph.D. Thesis, Purdue University, 1978. 

The physico-chemical properties of the analytes and the way they reach the detector have made atomic spectroscopy the detection technique of choice in most instances. A heated quartz cell or a similar device is connected directly to the gas outlet of the separation cell [26]. The use of an atomic fluorescence detector has provided methods for selenium [25,27] and mercury [28,29] that possess excellent analytical features and use inexpensive instruments. On a less affordable level are ICP emission [30] and atomic emission cavity spectrometers [31]. 

The identification of the chemical forms of an element has become an important and challenging research area in environmental and biomedical studies. Two complementary techniques are necessary for trace element speciation. One provides an efficient and reliable separation procedure, and the other provides adequate detection and quantitation [4]. In its various analytical manifestations, chromatography is a powerful tool for the separation of a vast variety of chemical species. Some popular chromatographic detectors, such flame ionization (FID) and thermal conductivity (TCD) detectors are bulk-property detectors, responding to changes produced by eluates in a characteristic mobile-phase physical property [5]. These detectors are effectively universal, but they provide little specific information about the nature of the separated chemical species. Atomic spectroscopy offers the possibility of selectively detecting a wide rang of metals and nonmetals. The use of detectors responsive only to selected elements in a multicomponent mixture drastically reduces the constraints placed on the separation step, as only those components in the mixture which contain the element of interest will be detected... 

In addition to the continuum sources just discussed, line sources are also important for use in the UV/visible region. Low-pressure mercury arc lamps are very common sources that are used in liquid chromatography detectors. The dominant line emitted by these sources is the 253.7-nm Hg line. Hollow-cathode lamps are also common line sources that are specifically used for atomic absorption spectroscopy, as discussed in Chapter 28. Lasers (see Feature 25-1) have also been used in molecular and atomic spectroscopy, both for single-wavelength and for scanning applications. Tunable dye lasers can be scanned over wavelength ranges of several hundred nanometers when more than one dye is used. 

The silicon intensified target (SIT) vidicon has a number of unique properties which make it a valuable detector for atomic spectroscopy. The SIT vidicon provides two-dimensional photoelectric detection with high sensitivity and rapid signal readout. Time resolution can be obtained in a time-resolved (real time) mode on the millisecond scale and in a time-gated (equivalent time) mode on the submicrosecond scale. 

I) Analytical technique or method, occasionally unfeasible with the Involvement of an operator —this book abounds In Illustrative examples of this kind. Thus, electrothermal vaporization atomic absorption spectroscopy demands the automation of the sample thermal treatment In the graphite tube via a microprocessor programming the different heating stages involved (automation of methodology). Likewise, the use of Image detectors In spectroscopy calls for computerized data acquisition, impossible with manual operators. 

Beanland. r.lectron Microscopy and Analysis, 3rd ed.. London Taylor and Francis. 2001. p. 123.) (b) A nine-micromirror array used lo develop digital micromirror spectrometer for atomic spectroscopy, Mirrors are 16 16 pm on 17-pm centers. Removing the center mirror reveals underlying components. (From J. 1). Batchelor and B. T. Jones. Anal. Chem., 1998, 70. 4907. Copyright 1998 American Chemical Society.) (c An algae mat taken in fully wet condition wilh an ESEM instrument with a gas-phase secondary-eleclron detector with cascade amplification. No sample preparation was needed, From P. J. Goodhew. J. Flumphreys, and R. Beanland. Electron Microscc y sncf Analysis 3rd ed.. London Taylor and Francis. 2001. p. 167 )... 

The most important applications for diode array systems are in molecular spectroscopy, since in general they do not have the resolution necessary for atomic spectroscopy. In molecular spectroscopy the most useful areas of application are for (1) scanning fast reactions to determine kinetics, (2) applications involving low light levels because spectra can be stored and added to each other, increasing the intensity, and (3) detectors for HPLC and capillary electrophoresis (CE). HPLC and CE are discussed in Chapter 13. 

Hewitt CN (1989) Atomic absorption detectors. In Harrison RM and Rapsomanikis S (eds.) Environmental Analysis Using Chromatography Interfaced with Atomic Spectroscopy, p. 53. New York WUey. 

Several detectors used in high-performance liquid chromatography (HPLC) and in supercritical fluid chromatography (SEC) can be connected to the CCC column to detect solutes and thus follow separation. They can be, for instance, fluorimeters (very sensitive and used without modifications in CCC), UV-Visible spectroscopes, evaporative fight scattering detectors, atomic emission spectroscopes, etc. Some detectors give more information than the detection of the solute, such as stmctural information of separated components, as in infrared spectroscopy, " mass spectrometry,or nuclear magnetic resonance. These detectors are... 

In the atomic spectroscopy experiment in Figure 20-1, a liquid sample is aspirated (sucked) through a plastic tube into a flame that is hot enough to break molecules apart into atoms. The concentration of an element in the flame is measured by absorption or emission of radiation. For atomic absorption spectroscopy, radiation of the correct frequency is passed through the flame (Figure 20-2) and the intensity of transmitted radiation is measured. For atomic emission spectroscopy, no lamp is required. Radiation is emitted by hot atoms whose electrons have been promoted to excited states in the flame. For both experiments in Figure 20-2, a monochromator selects the wavelength that will reach the detector. Analyte concentrations at the parts per million level are measured with a precision of 2%. To analyze major constituents, a sample must be diluted to reduce concentrations to the ppm level. Box 20-1 describes an application of atomic emission for space exploration. 

Another method included in this chapter is ICP-MS, which, although not based on atomic spectroscopy in a true sense, utilizes the same instrumental approach as ICP-AES for sample introduction. The difference is that analyte quantification takes place using a mass spectroscopy detector. 

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