Sharpening of peaks

The third model is a shift to higher frequencies and concomitant broadening of the resonance peak, due to increased 6s electron density in the eluster. Here use was made of the expected increase of 6s electron density due to the decrease in cluster volume, as obtained from EXAFS [39,40,41]. But as we have pointed out above, despite the decrease in cluster volume, the I.S. of the core sites indicates a decrease of 6s electron density. The excellent prediction of the I.S. values of the surface sites, given above, utilizing a sizeable increase in d-character of the electrons associated with (in the vicinity of) the surface sites, means that the postulated blue shift and flattening should really be a red shift and concomitant sharpening of the resonance, which should make the resonance more visible, if present. The MES I.S. results thus refute this as a possible explanation. 

Figure 9-2 A gas-liquid chromatogram of a mixture of the isomeric butanols at constant column temperature. A tiny peak on the far left is a trace of air injected with the sample. The retention times of the various isomers are in the same order as the boiling points, which are, from left to right, 82°, 99.5°, 108°, and 117°. The areas under each peak correspond to the relative amounts of material present. Raising the column temperature at a preprogrammed rate while developing the chromatogram speeds up the removal of the slower-moving components and sharpens their peaks. Also, by diversion of the gas stream to appropriate cold traps it is possible to collect pure fractions of each component.

Fig. 10.5 FT-IR spectra of C60 (in KBr). On lowering the temperature from +250°C to -180°C the absorption peak originally located at 1178 cnr1 shifts at higher frequencies i.e. 1182 cm-1. Additionally, the bandwidth is reduced from 8.95 to 7.97 cnr1 respectively from +250°C to -180°C and the peak area passes from 2.275 to 2.400 since at lower temperature there is a sharpening of the absorption band but also an increase in intensity...

It is evident from the above expressions that the appropriate diffusion coefficient must also be measured in order that molecular or particle masses may be determined from sedimentation velocity data. In this respect, a separate experiment is required, since the diffusion coefficient cannot be determined accurately in situ, because there is a certain self-sharpening of the peak due to the sedimentation coefficient increasing with decreasing concentration. 

How can this be solved Clearly there are limits to the amount of peak sharpening that is practicable, but the filter function can be improved so that noise reduction and resolution enhancement are applied simultaneously. One common method is to multiply... 

Several scientific reports about SFC indicate that the chromatographic retention mechanisms of charged analytes in the presence of suitable ionic modifiers involve ion-pairing [14]. Ion-pairing of sulfonates with ammoninm salt additives was effectively exploited to enhance the solvating power of the mobile phase [15] and sharpen analyte peaks [16], The use of ammonium acetate produced unique results (see Figure 15.1). Ion-pairing also explained enantioselectivity when chiral analytes were analyzed with packed columns in the presence of chiral connter ions [17]. An achiral IPR under SFC conditions played a crucial role in the enantioseparation of a variety of amines [18] for reason explained in Section 13.6. 

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