Resolution, also

The spatial resolution of the CI SEM mode depends mainly on the electron-probe size, the size of the excitation volume, which is related to the electron-beam penetration range in the material (see the articles on SEM and EPMA), and the minority carrier diffusion. The spatial resolution also may be afiFected by the signal-to-noise ratio, mechanical vibrations, and electromagnetic interference. In practice, the spatial resolution is determined basically by the size of the excitation volume, and will be between about 0.1 and 1 pm ... 

The depth resolution of ERDA is mainly determined by the energy resolution of the detector system, the scattering geometry, and the type of projectiles and recoils. The depth resolution also depends on the depth analyzed, because of energy straggling and multiple scattering. The relative importance of different contributions to the depth resolution were studied for some specific ERDA arrangements [3.161, 3.163]. 

It is still possible to enhance the resolution also when the point-spread function is unknown. For instance, the resolution is improved by subtracting the second-derivative g x) from the measured signal g x). Thus the signal is restored by ag x) - (7 - a)g Xx) with 0 < a < 1. This llgorithm is called pseudo-deconvolution. Because the second-derivative of any bell-shaped peak is negative between the two inflection points (second-derivative is zero) and positive elsewhere, the subtraction makes the top higher and narrows the wings, which results in a better resolution (see Fig. 40.30). Pseudo-deconvolution methods can correct for sym-... 

The sensitivity depends on the mode of operation. In the full scan mode the sensitivity is limited, while in the selected ion monitoring mode the sensitivity is high. The desired resolution also affects sensitivity (see above). 

The above remark about resolution also applies to electron diffraction, and in fact, resolution is one of the most serious limitations in structure determination based on electron diffraction from powder samples. The poor... 

Insufficient resolution leads to a decrease in the extinction coefficient across the wavelength axis, and therefore inaccurate quantitation results. The sensitivity of the measurement is also compromised. From a qualitative point of view, the fine features in the spectrum may be lost. The resolution of a UV-Vis spectrophotometer is related to its spectral bandwidth (SBW). The smaller the spectral bandwidth, the finer the resolution. The SBW depends on the slit width and the dispersive power of the monochrometer. Typically, only spectrophotometers designed for high-resolution work have a variable slit width. Spectrophotometers for routine analysis usually have a fixed slit width. For diode array instruments, the resolution also depends on the number of diodes in the array. 

Figure 57. Spectra of Ac=-1 sequence of 1 TV) resulting from impact of Ar+, N +, and He on N2, taken at 0.4-nm spectral resolution. Also shown are fractional intensities calculated assuming occurrence of vertical transitions. Fractional intensity scale is chosen so that (0,1) bar corresponds to (0,1) band for He2+-N2.391... 

In spite of the development of more successful and reliable CSPs (Chaps. 2-8), these miscellaneous types of CSP have their role in the field of the chiral resolution also. The importance of these CSPs ties in the fact that they are readily available, inexpensive, and economic. Moreover, these CSPs can be used for some specific chiral resolution purpose. For example, the CSP based on the poly(triphenylmethyl methacrylate) polymer can be used for the chiral resolution of the racemic compounds which do not have any functional group. The CSPs based on the synthetic polymers are, generally, inert and, therefore, can be used with a variety of mobile phases. The development of CSPs based on the molecularly imprinted technique has resulted in various successful chiral resolutions. The importance and application of these imprinted CSPs lies in the fact that the chiral resolution can be predicted on these CSPs and, hence, the experimental conditions can be designed easily without greater efforts. Because of the ease of preparation and the inexpensive nature of these CSPs, they may be useful and effective CSPs for chiral resolution. Briefly, the future of these types of CSP, especially synthetic polymers and polymers prepared by the molecularly imprinted technique, is very bright and will increase in importance in the near future. 

Increasing the resolution also allows the separation and differentiation of endogenous compounds in biological matrices from a drug of interest or its metabolites. A comparison of mass spectra of sulfacetamide obtained using a quadmpole mass spectrometer (unit mass resolution) with that obtained using a time-of-flight mass spectrometer (R = 10,000) is shown in Fig. 4.9. While at unit mass resolution the... 

NMR spectroscopy has been an extraordinary important technique for structure determination of hydrogenated fullerenes ever since the first synthesis of hydrogenated fullerenes almost two decades ago. During this time, technical advances have pushed the limits regarding both sensitivity and spectral resolution. Also, sophisticated 2D NMR experiments have been implemented more and more frequently in recent years. Consequently, NMR spectroscopy has now been used to successfully characterize complex hydrogenated fullerenes whose structure for a long time... 

All these expressions give approximate values of resolution also, the smaller the distance between target peaks in the chromatogram, the closer the values to the true resolution. Detailed analysis of available master resolution equations is given in the B. Karger article [4]. 

The Resolution also states that rubber products of Categories 1 and 11 should not transfer their constituents to foodstuffs or food simulants in total quantities above an overall migration limit (OML) of 60 mg/kg food or food simulant. 

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