Spectroscopic detection method

Hefter U and Bergmann K 1988 Spectroscopic detection methods Atomic and Moiecuiar Beam Methods vol 1, ed G Scoles et a/(New York Oxford University Press) pp 193-253... 

The density here refers to the spatial coordinate, i.e. the concentration of the reaction product, and is not to be confused with the D(vx,vy,vz) in previous sections which refers to the center-of-mass velocity space. Laser spectroscopic detection methods in general measure the number of product particles within the detection volume rather than a flux, which is proportional to the reaction rate, emerging from it. Thus, products recoiling at low laboratory velocities will be detected more efficiently than those with higher velocities. The correction for this laboratory velocity-dependent detection efficiency is called a density-to-flux transformation.40 It is a 3D space- and time-resolved problem and is usually treated by a Monte Carlo simulation.41,42... 

Electrochemical (EC) detectors have been used for detection in CE. EC methods offer an advantage over the spectroscopic detection methods because electrochemistry that occurs directly at an electrode surface is not limited by the small dimensions inherent in The... 

Despite the short lifetimes of most silylenes, improvements in flash photolysis techniques for their generation and time-resolved spectroscopic detection methods in the past decade have made possible direct kinetic measurements on the reactions of silylenes. The purpose of these kinetic studies has been to elucidate the mechanisms of silylene reactions. While considerable work remains to be done, transition state structures and activation barriers are emerging from these experiments, and aspects of silylene insertion and addition mechanisms have been revealed that were not uncovered by product studies and were, indeed, unexpected. 

The currently employed method of quantifying blood CO and the precaution that is needed for accuracy are simply refinements of the method described by Haldane (1895b, 1896) more than a century ago colorimetric detection was soon replaced by the spectroscopic detection method (Hartridge, 1912) and has undergone further sophistication since then. Both gas chromatography and spectrophotometry are considered appropriate although the former is favored (Cobum et al, 1964 Collison et al, 1968 ... 

By now most of the studies were carried out using nanosecond pulse radiolysis techniques coupled with spectroscopic detection method, only a few were reported to use muonium reactions, ° steady state (7 )radiolysis, laser phtolysis, and picosecond pulse radiolysis. Since conventional pulse radiolysis techniques are well known, here we just briefly introduce the high temperature high pressure (HTHP)... 

Nonuniformity of the layer or of the sample distribution in the layer and light scattering are some of the difficulties that an on-line spectroscopic detection method has to overcome. 

Hyphenation refers to the online combination of a separation technique (mainly GC or LC) and a spectroscopic detection method that provides structural information for the analytes concerned. LC-MS and GC-MS are the most popular hyphenated techniques in use today, thanks to the incredible shrinking of mass spectrometers. However, MS does not provide the same information as IR or NMR. Hypernation (one higher than hyphenation) is the multiple hyphenation which may combine, for example, UV detection with PDA, NMR, FTIR, and MS as displayed in Figure 4.22, the last one is a destmctive detector. At the present time most analysts are using a single detector but it can be guessed that hypemation will be used more and more as size and cost of the instruments decrease. 

Thus, any successful kinetic analysis requires an optimal choice of the spectroscopic detection method, whereby special methods (e.g. pre-separation by chromatography) or modem approaches (e.g. interferometry) must also be considered. Therefore in the following sections different approaches in spectroscopy are presented, some combined irradiation and measurement devices introduced, and different set-ups classified with respect to their principle of operation (sequential, multiplex, single and double beam equipment). In addition some special devices are presented which allow an automated examination even of complex photochemical reactions (in part superimposed by thermal reactions) at a highly sophisticated level using various combinations of modem equipment and supplying data for multicomponent analysis. 

High performance liquid chromatography (HPLC) is used routinely in phytochemistry to "pilot" the preparative isolation of natural products (optimisation of the experimental conditions, checking of the different fractions throughout the separation) and to control the final purity of the isolated compounds [2]. HPLC is the most well fitted technique for an efficient separation of crude plant extracts and can be coupled with different spectroscopic detection methods. 

V. Hefter, K. Bergmann, Spectroscopic detection methods, in Atomic and Molecular Beam Methods, vol. 1, ed. by G. Scoles (Oxford Univ. Press, New York, 1988), p. 193 J.E.M. Goldsmith, Recent advances in flame diagnostics using fluorescence and ionisation techniques, in Laser Spectroscopy VIII, ed. by S. Svanbeig, W. Persson. Springer Ser. Opt. Sci., vol. 55 (Springer, Berlin, 1987), p. 337... 

On the other hand, spectroscopic detection methods, such as laser-induced fluorescence, UV/Vis absorption, chemiluminescence, and thermal lens microscopy, have been used for on-chip detection. Among these methods, the fluorescence detection method has been most widely used because of its high sensitivity and low detection limits for biologically relevant species. However, the fluorescence detection technique has some disadvantages. Many chemical... 

For the detection of the separated ions, spectro-photometric and other spectroscopic detection methods are used. 

V. Hefter, K. Bergmann Spectroscopic detection methods . In Atomic and Molecular Beam Methods, Vol.l, ed. by G. Scoles (Oxford Univ. Press, New York 1988) p. 193... 

M. Kappes and S. Leutwyler, Spectroscopic Detection Methods in Atomic and Molecular Beam Methods, G. Scoles (ed.) (Oxford University Press, New York, 1988), Vol. 1, Chap. 15, p 380. 

Pascoa, R. N. M. J., I. V. Toth, and A. O. S. S. Rangel. 2012. Review on recent applications of the liquid waveguide capillary cell in flow based analysis techniques to enhance the sensitivity of spectroscopic detection methods. Anal. Chint. Acta 739 1-13. 

Compared with conventional methods of measuring velocity distributions with mechanical selectors or with conventional time-of-flight tubes, this spectroscopic detection method has the following advantages ... 

D. Bushee, I.S. Krull, R.N. Savage, and S.B. Smith, Jr. Metal cation/anion speciation via paired-ion, reversed phase HPLC with refractive index and/or inductively coupled plasma emission spectroscopic detection methods. J. Liquid Chrom., 5, 563 (1982). 

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