Resolving power, intrinsic

CE provides analysis based on orthogonal separation principles compared to other techniques as well as high resolving power. Like slab gel electrophoresis, CE is a family of techniques that resolve sample components by differences in intrinsic molecular characteristics such as size, mass, charge, differential interaction, and isoelectric point (pi). 

While 2D separations arc technically more difficult to carry out than those in one dimension, and often subject to less convenient detection methods, their intrinsic resolving power and potential scope are sufficiently greater than those of one-dimensional systems that many important gains can be expected in the future. 

The intrinsic precision and resolving power of MLC facilitate the routine observation of MS-RTP for three major reasons ... 

For modem time of flight (TOF) analyzers that can provide resolving power (FWHM definition) >10 via incorporation of the ion detector as an intrinsic component of the m/z analysis, such CEM response time characteristics are inadequate. This is easily illustrated by an ullra-simplified calculation for a typical case in which the spatial and time focusing properties of the TOF analyzer (Section 6.4.7) are sufficient that the resolving power (RP) is limited by the time response of the detector. The time of flight of an ion is given by Equation [6.19] ... 

In practice, the ability to resolve between atoms exhibiting slightly different chemical shifts is limited by the peak widths which are governed by a combination of factors especially the intrinsic width of the initial level and the lifetime of the final state, the line-width of the incident radiation (which for traditional X-ray sources can only be improved by using X-ray monochromators) and the resolving power of the electron-energy analyzer. In most cases, the second factor is the major contributor to the overall line width. 

In a time-resolved experiment, the intrinsic polarization of the system is measured with very little correction except for power saturation (98,99). To measure the initial polarization, the signal heights S and Sq (hence the enhancement factor V and the polarization factor P = /So) can be obtained directly from the time profile. For a photo-CIDEP system induced only by the triplet mechanism and the triplet reaction involves a substrate SH, a kinetic analysis yields the following relationship ... 

Let us now examine the two minor disadvantages of the laser time-resolved experiments which we mentioned briefly. The low radical concentration normally encountered in such experiments makes evaluation of E-A-type polarization difficult. In fact, even when the radical concentration is not a problem, as in pulse radiolysis study, the time profile has to be fitted to obtain the enhancement factor (124). Another aspect in the time-resolved study is that the experiments have to be repeated at different microwave power levels, as the true intrinsic P or V can only be obtained by extrapolation to zero power. Ironically, these two problems can be overcome readily in semi-steady-state experiments using a conventional slow-response spectrometer. 

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