Detectors unique

SFE-GC is an attractive approach to coupling the extraction, concentration and chromatographic steps for the analysis of samples containing analytes that can be analysed using capillary GC. Often it is difficult to identify all the components which are extracted from samples by FID alone. This is a particular problem when the sample history and/or the identity of the compounds of interest are not known. When SFE-GC is combined to powerful spectroscopic detectors, unique data can be obtained, allowing their use as routine tools in the analytical laboratory. For positive identification of components of interest, multihyphenated techniques such as SFE-GC-AED, SFE-GC-MS, SFE-GC-FUR-MS are employed [46]. 

If the detection system is an electronic, area detector, the crystal may be mounted with a convenient crystal direction parallel to an axis about which it may be rotated under tlie control of a computer that also records the diffracted intensities. Because tlie orientation of the crystal is known at the time an x-ray photon or neutron is detected at a particular point on the detector, the indices of the crystal planes causing the diffraction are uniquely detemiined. If... 

As with gas chromatography, numerous detectors have been developed for use in monitoring HPLC separations. To date, the majority of HPLC detectors are not unique to the method, but are either stand-alone instruments or modified versions of the same. 

MEIS has proven to be a powerful and intuitive tool for the study of the composition and geometrical structure of surfaces and interfaces several layers below a surface. The fact that the technique is truly quantitative is all but unique in surface science. The use of very high resolution depth profiling, made possible by the high-resolution energy detectors in MEIS, will find increased applicability in many areas of materials science. With continued technical development, resulting in less costly instrumentation, the technique should become of even wider importance in the years to come. 

Although the OTHdC has several unique applications in polymer analysis, this technique has several limitations. First, it requires the instrumentation of capillary HPLC, especially the injector and detector, which is not as popular as packed column chromatography at this time. Second, as discussed previously, the separation range of a uniform capillary column is rather narrow. Third, it is difficult to couple capillary columns with different sizes together as SEC columns. 

The diode array detector can be used in a number of unique ways and an example of the use of a diode array detector to verify the purity of a given solute is shown in figure 9. 

The refractive index detector, in general, is a choice of last resort and is used for those applications where, for one reason or another, all other detectors are inappropriate or impractical. However, the detector has one particular area of application for which it is unique and that is in the separation and analysis of polymers. In general, for those polymers that contain more than six monomer units, the refractive index is directly proportional to the concentration of the polymer and is practically independent of the molecular weight. Thus, a quantitative analysis of a polymer mixture can be obtained by the simple normalization of the peak areas in the chromatogram, there being no need for the use of individual response factors. Some typical specifications for the refractive index detector are as follows ... 

It is seen that however sophisticated the software might be, it would be virtually impossible to de-convolute the peak into the three components. The peaks shown in the diagram are discernible because the peaks themselves were assumed and the composite envelope calculated. The envelope, however, would provide no basic data there is no hint of an approximate position for any peak maximum and absolutely no indication of the peak width of any of the components. The use of the diode array detector, monitoring at different wavelengths, might help by identifying uniquely one or more of the... 

With proper design, fabrication and clocking, most of these negative aspects can be overcome, but there are usually some bad columns due to blocked columns or hot pixels. There are many positive aspects of charge transfer, giving the CCD some very good and unique attributes vis-a-vis an infrared detector ... 

For a radio astronomer, a star is a source of noise this noise can be detected and correlated from antenna to antenna in order to position precisely the source. For optical observer, the star is a source of photons, the unique photon goes through a variety of optical paths and materialize on the focal plane detector. 

Lunte et al. have recently developed a unique voltammetric detector using... 

A detailed description of analytical techniques is given in a number of original articles and books [3]. We will focus our interest on comparison of capacities of the mentioned physical and chemical methods with those of semiconductor detectors (SCD) or semiconductor sensors (SCS). These detectors are growing popular in experimental studies. They are unique from the stand-point of their application in various branches of chemistry, physics, and biology. They are capable of solving numerous engineering, environmental and other problems. 

Therefore, the use of a combination of sensors (sensor-substrate and sensor-detector of emitted atoms) enabled us to obtain unique information concerning the mechanism of emission of adsorbed atoms of silver in the course of their surface aggregation. The data obtained makes it possible to provide an insight of mechanisms and energetics of condensation-stimulated phenomena [11]. 

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