Apparent integrated intensity

Assuming the true absorptions to have Lorentzian form and assuming a triangular slit function, Ramsay 121, 122) investigated the effect of finite resolving power upon these band shapes for the vibrations of a variety of compounds. This approach reproduced satisfactorily the observed band profiles. However, he did not obtain a simple relationship between true and apparent integrated intensities. Ramsay found that bands are best characterized by their apparent peak intensities [loge(J o/r) J and their apparent half-intensity band widths These quantities are related to... 

Analysis of Defined Fractions. Quantitative infrared analysis was used for those fractional groups that have definitive bands average absorptivities were estimated using model compounds (12, 16, 17). Table I lists the infrared bands and the apparent integrated absorption intensities (B) used. Quantitative IR spectra were measured in methylene chloride with 0.05 cm sodium chloride cells, using a Perkin-Elmer 521 infrared spectrophotometer. Peak area was measured by planimetry. Molecular weights were determined by vapor-pressure osmometry in benzene. 

Table I. Infrared Assignments and Apparent Integrated Absorption Intensity...

The data reported by Basila et al. (221,224) lead to a value of 1.6 03. Using the apparent integrated absorption intensities as given by Hughes and White (198), Ward and Hansford (226) estimated the limits of detection of Br nsted acidity to be of the order of magnitude of 10 2 meq g-1 for silica-aluminas with Brunauer-Emmett-Teller (BET) surface areas between 350 and 500 m2 /g. 

Because of the use of finite slit widths, the radiation is not monochromatic (and covers an appreciable part of the band envelope) and the measured quantity is an apparent integrated absorption intensity (B),... 

Since the two ratios of the right-hand side of Eq. (14) have been tabulated, it is easy to present K in the same form so that by measuring the apparent peak intensity and the apparent half-intensity band width of an absorption band and consulting the relevant tables, the true integrated absorption intensity can be calculated from Eq. (13). 

The experiment described above is termed selective population transfer (SPT), or more precisely in this case with proton spin inversion, selective population inversion, (SPI). It is important to note, however, that the complete inversion of spin populations is not a requirement for the SPT effect to manifest itself. Any unequal perturbation of the lines within a multiplet will suffice, so, for example, saturation of one proton line would also have altered the intensities of the carbon resonance. In heteronuclear polarisation (population) transfer experiments, it is the heterospin-coupled satellites of the parent proton resonance that must be subject to the perturbation to induce SPT. The effect is not restricted to heteronuclear systems and can appear in proton spectra when homonuclear-coupled multiplets are subject to unsymmetrical saturation. Fig. 4.20 illustrates the effect of selectively but unevenly saturating a double doublet and shows the resulting intensity distortions in the multiplet structure of its coupled partner, which are most apparent in a difference spectrum. Despite these distortions, the integrated intensity of the proton multiplet is unaffected by the presence of the SPT because of the equal positive and negative contributions (see Fig. 4.19d). Distortions of this sort have particular relevance to the NOE difference experiment described in Chapter 8. 

It has been repeatedly reported that silver stained methods are not suitable for computerized quantitation because of their capriciousness and nonlinearity. This is apparently true of the stains based on reduction with citric acid and weak carbonate because there is no predicting the slope of a plot of integrated intensity versus protein concentration without the use of a reliable and reproducible color. Thus, in order to use quantitation with these two methods one must perform a standard curve with each protein as its own standard or accept some relative standard for normalization. The relative approach has been successfully used with GELCODE and allowed measurement of protein changes within an experimental protocol (1 ). These disadvantages have discouraged the acceptance of silver staining to its full potential application. 

Apparent integrated absorption intensity, J dv, according to Eq. (27) the respective values are not indicated in Table 2 by superscript a . 

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