Information spectral, multichannel

Extracting analyte concentrations from spectra of complex systems containing multiple analyte contributions with overlapping spectral features requires more information than is obtainable in a single wavelength measurement. Multivariate techniques take the full-range spectrum into account and exploit the multichannel (data at many wavelengths) nature of spectroscopic data to extract concentration information from analytes.19 20... 

Unfortunately, the LC-MS combination is less successful. In part, this may be due to technological interfacing problems, but even if these are solved, LC-MS is unlikely to provide the same degree of universality (large molecules will remain a problem), spectral information and reproducibility as the GC-MS combination. For the moment, the combination of LC with a multichannel UV absorption detector is a more realistic proposition. 

The acquisition of the spectral information from each single spark separately is now possible with advanced measurement systems, using integration in a small capacitor and rapid computer-controlled readout combined with storage in a multichannel analyzer. With the aid of statistical analysis, sparks with outlier signals can be rejected and the precision improved accordingly. Furthermore, pulse differential height analysis enables discrimination between a number of elements such... 

A microscopic fluorescence spectrum is potentially very informative, since it reflects stoichiometric ratios, efficiencies of electronic excitation transfers among the pigment-protein complexes, and quenching mechanisms inherent in the photo synthetic reactions. Since the multiple fluorescence bands are overlapping, spectral detection based on a polychromator and multichannel detector is more informative than detection using a few channels based on dichroic mirrors and band-pass filters. 

The new computerized spectrofluorimeters in combination with the availability of selective multichannel detectors allow for a reliable and quick collection and analysis of spectral information that was difficult to accomplish using a single-wavelength scan. The new multichannel detectors used for making multiwavelength measurements also allow the ability to study a wide variety of multicomponent samples. 

In view of the resolution characteristics of an ED detector, spectral overlap interferences are much more common in ED-XRE than WD-XRF and require a more comprehensive correction procedure than the simple line ratio method often used in the latter technique. However, advantage can be taken of the digital form in which ED spectral data are accumulated in the multichannel analyzer, which offers information about peakshapes as well as intensity. For simple ED spectra, it may be possible to define a series of windows covering each fluorescence peak of interest (the region-of-interest approach). Peak intensities can then be determined by chaimel integration and a background correction applied by linear interpolation between the lowest and the highest channel of the window. For complex spectra, a more sophisticated approach is required, of which two have found widespread use. 

Since the spectral information seen by the individual pixel is recorded simultaneously, an array with n pixels is equivalent to n spectrometers working separately or one spectrometer working n times. Simultaneous recording of n pixels provides the multichannel advantage. 

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