Peak Measurements

Displacement peak-to-peak measure = lA Velocity maximum measure = Alo Acceleration maximum measure = Au ... 

The peak width (w) is the distance between each side of a peak measured at 0.6065 of the peak height. The peak width measured at this height is equivalent to two standard deviations (2o) of the Gaussian curve and, thus, has significance when... 

The peak measured for a plate number determination contains additional information about the packing quality of a column. The same peak may also be used to quantify information about the shape as well. The peak width on both sides of the perpendicular through the peak maximum is measured at a height of 10% of the maximum height (see Fig. 14.2). The quotient of the back by the front part of the peak is defined as the asymmetry factor (AF) ... 

Phototubes, multiplier, 56-59, 222 Placement error, 285-287 Planck s constant, 7, 8 Plastics, characterization by absorptiometry, 78, 79 Plateau, characteristic, 60 Platinum, determination by x-ray emission spectrography, 161, 328 L peaks, measured by Bragg, 25, 26, 35 L spectra, 35... 

Figure 40. PMC peak measured with a ZnO single-crystal electrode in a microwave resonator near the onset of the anodic photocurrent.5...

It is seen that there is not a great difference between the use of peak heights or peak areas for quantitative analysis, except possibly for very early peaks, where the results seem to indicate that peak height measurements might be more precise. However, it again must be emphasized that the measurements made by Scott and Reese were overall precision measurements that will include all variations in the chromatographic system. The difference between the two methods of measurement may well be significant, but the absolute values for precision will not, by any means, be solely dependent on the method of peak measurement. 

In the simplest approach T is the full width of the peak (measured in radians) subtended by the half maximum intensity (FWHM) corrected for the instrumental broadening. The correction for instrumental broadening is very important and can be omitted only if the instrumental broadening is much less than the FWHM of the studied diffraction profile, which is always the case in presence of small nanoclusters. The integral breadth can be used in order to evaluate the crystallite size. In the case of Gaussian peak shape, it is ... 

If no exothermic peak appears up to 500 K in DTA/DSC curves for heating rates of 5-10 K min and no other signs of vigorous reaction are observed, then the material can usually be considered safe. In case of the occurrence of a temperature peak, measurements should be repeated at lower heating rate. 

Amplifier noise on large peaks measured via Faraday cups ... 

FIGURE 6.8 Comparison of typical (a) In3d and (b) Sn3d XPS peaks measured for ITO films prepared at different hydrogen partial pressures of 0, 7.9x 10 6, and 1,6x 10-5 torr. 

Obtain a chromatogram of your unknown. The peaks will be smaller since the concentrations are not 100%, as they were for the pure liquids. You may have to adjust the attenuation to get large, well-defined peaks. Measure the retention times for each peak, and compare these to your data for the pure liquids. Those liquids that have retention times matching a peak in your unknown are contained in your unknown. 

The last term produces a cross peak at coq,cohj due to coherence transfer between 4HizCixCjj and AHjzCjxQr In the experiment with A = 0, the intensity of the cross peak (j-crass) jg pr0p0rtional to sinh(rcCjH, chJm), whereas for A = 1/2JCh the intensity of the cross peak (Tef) is proportional to cosh(TqH, CjH/m)- By comparing the intensity of the cross peak measured in the two experiments one can determine... 

For external standardization, replicate standards of known concentration of the pure substance are injected and the height of the resulting peaks measured. The sample is then injected and the peak height compared with those of the standards to calculate the concentration of the test. In using this technique, replicate injections of both the standards and the test must be made. 

Table 1 also contains some peak measurement/analysis parameters that might be investigated in a robustness test (see Section III.C). ° However, except from the detection wavelength, these parameters are hardly ever evaluated in a robustness test, even though they can have a large influence on the electropherogram. 

Operational and environmental factors Peak measurement/analysis parameters... 

FIGURE 3 Two electropherograms from one run, recorded with different settings for peak measurement/analysis parameters. 

In reference 20, a typical robustness test is not performed, but a study on the influence of peak measurement parameters is reported on the outcome. The study is special in the sense that no physicochemical parameter in the experimental runs is changed, but only data measurement and treatment-related parameters. These parameters can largely affect the reported results, as shown earlier, and in that sense they do influence the robusmess of the method. The different parameters (see above) were first screened in a two-level D-optimal design (9 factors in 10 experiments). The most important were then examined in a face-centered CCD, and conclusions were drawn from the response surfaces plots. 

Perrin, C., Fabre, H., Massart, D. L., and Vander Heyden, Y. (2003). Influence of peak measurement parameters on the quality of chiral electrophoretic separations. Electrophoresis 24, 2469—2480. 

Verify a True Peak measurement instrument by first establishing an initial calibration nsing a sine wave. Then verify the pulse response of the instrument nsing a nonsymmetrical duty cycle pulse and compare the results to the sine wave calibration. Follow these steps ... 

Harrison, R. M., and J. D. Peak, Measurements of Concentration Gradients of HN02 and HNO-, over a Semi-Natural Ecosystem Discussion, Atmos. Enriron., 31, 2891-2892 (1997). 

The chromatogram of the sample for which A /A V) — 9/14 (heights of the peaks measured from the original chromatogram), leads to... 

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