Half-height, peak width

Plotting the peak potentials as a function of the logarithm of the scan rate allows one to determine the transfer coefficient from the slope of the resulting straight fine in the total irreversibility region. Another possibility for determining a is to measure the half-height peak widths ... 

X-ray diffraction patterns of the lead-substituted lead ruthenates support the conclusion that they are pyrochlores of cubic symmetry. It must be noted, however, that since these materials were prepared at relatively low temperatures, the peaks in their x-ray spectra were broadened. X-ray line broadening was significant [half-height peak width at 50-60 (20) was equal to 0.5-0.8 (20)] thus any subtle evidence of distortion to lower symmetries would be difficult to... 

Depending on the dimensions and constmction of the composite cantilever, resonance frequencies were observed in the range of 0.7 to 1.2 MHz. The resonance spectra (Fig. IB) in vacuum ( 50 mTorr, 23.6 °C), in air (23.6 °C) and in phosphate buffered saline (lOmM, PBS 30 °C) are shown for the dominant high-order mode at 941.5 kHz in air (Q = 41). The parameter Q is a measure of peak sharpness and is equal to the ratio of resonance frequency to half-height peak width. When mounted in a specially constructed sample flow cell and PBS is flowed in at 0.4 to 1.0 mL/min, the resonant frequency decreased ( 50 kHz) due to added mass effect and the peak height decreased by 20 to 60%. At 1 mL/min, Q-value remained sufficiently high ( 23), that the resonant frequency can be measured with an accuracy of 20-40 Hz. Resonant frequency in... 

Note that (i) The plate numbers are slightly higher when half-height peak widths are used to calculate them due to peak tailing increasing W( hence comparisons of efficiencies are valid only if the same formula is used throughout. 

Width at half-height Peak-to-peak width... 

Area Method—Measare the area of each component by multiplying the height of the peak by the width at half height. The width should be measured with the aid of a magnifying glass (Note 3). Adjust the area to the attenuation of the same component in the reference standard mixture. 

The full width at half height of these Lorentzian peaks is 2/x. One says that the individual peaks have been pressure or eollisionally broadened. 

Narrow transitions (small a) yield large peak voltages and narrow pulse shapes (PIF q). The width at half height is given by equation 4 where... 

Q are the absorbance and wavenumber, respectively, at the peak (center) of the band, p is the wavenumber, and y is the half width of the band at half height. Liquid band positions ate usually shifted slightly downward from vapor positions. Both band positions and widths of solute spectra are affected by solute—solvent interactions. Spectra of soHd-phase samples are similar to those of Hquids, but intermolecular interactions in soHds can be nonisotropic. In spectra of crystalline samples, vibrational bands tend to be sharper and may spHt in two, and new bands may also appear. If polarized infrared radiation is used, both crystalline samples and stressed amorphous samples (such as a stretched polymer film) show directional effects (28,29). 

The peak width at half height (wq.s) is the distance between each side of a peak, measured at half the peak height. The peak width measured at half height has no significance with respect to chromatography theory. 

FIGURE 2.13 From measurements of the retention volume, Vr, and the peak width at half peak height, Wr, of a gaussian peak, an estimate of column efficiency N and relative efficiency, HETP, may be calculated. The last figure is for very well packed columns close to 2 X dp. [Reproduced from Sofer and Hagel (1997), with permission.]... 

Half-Height Method. For an ideal Gaussian distribution the peak width Wb at the half of the maximal height is 2.355 or. If the width at the half-height is inserted in Eq. (1), we get... 

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