Spectra quantitative evaluation

Spectral Gamma Ray Log. This log makes use of a very efficient tool that records the individual response to the different radioactive minerals. These minerals include potassium-40 and the elements in the uranium family as well as those in the thorium family. The GR spectrum emitted by each element is made up of easily identifiable lines. As the result of the Compton effect, the counter records a continuous spectrum. The presence of potassium, uranium and thorium can be quantitatively evaluated only with the help of a computer that calculates in real time the amounts present. The counter consists of a crystal optically coupled to a photomultiplier. The radiation level is measured in several energy windows. 

On the basis of these experimental results and discussion, we tried to establish a convenient and useful method for quantitative evaluation of the molecular orientation in thin LB films using FT-IR transmission and RA spectra. Here, we assume a uniaxial orientation of the transition moment with an angle < > around the normal axis, Z, to the LB film surface i. e. the XY plane (Figure 8). In this case, the ratio of the absorbance of a particular band in the transmission spectrum, AT, to that of the same band in the RA spectrum, AR, is given by... 

Fig. 5.6. PFT 1 1H NMR spectra of D-ribose, 22.63 MHz. 1 g/2 mL D20, temperature 30 C, accumulation of 2000 pulse interferograms (6 K data points), 90 pulses, pulse interval 6 s, 2500 Hz, the numbers of the signals refer to the numbering of the C atoms. A quantitative evaluation of the spectrum gave 62% of /j-ribopyranosc (P (i), 20.3% of a-ribopyranose (Pa). 11.6% of /1-ribo-furanose (Ffi) and 6.1 % of a-ribofuranose (Fa) [132b],...

The VOCs in the inside air are enriched by means of active sampling on Tenax TA tubes, which are thermodesorbed. After internal standards have been added, analysis is carried out by capillary GC—MS. The hundred compounds on the chromatogram which have the most intense signals are identified by retention index and mass spectrum (Wensing, Schulze and Salthammer, 2002), and are then semi-quantitatively evaluated with toluene as the reference substance. The toluene equivalents are summed, and this result serves as a semi-quantitative estimation of the total VOC concentration (TVOC). 

Quantitative evaluation of molecular similarity. The fragment spectrum obtained in the above can be described as a kind of multidimensional pattern vector. Consequently, using this pattern representation of a spectrum it is possible to apply diverse quantitative methods for the evaluation of similarity. 

A quantitative evaluation of the EPR spectrum indicated that about 50% of the iron present in adrenodoxin contributes to the signal, assuming that there is only one unpaired electron associated with each iron atom and using the standard reference of 1 mM CUSO4. The results are shown in Table 8, which may indicate that the two iron atoms in adrenodoxin are not equivalent. 

Quantitative evaluation of the infrared spectrum is done with regard to the empiric tables or digital libraries. So this can be estimated quickly. For example, if sample contains aromatic groups, information can be collected in the infrared spectrum by looking for the peaks typical of the aromatic carbon. 

Quantitative evaluation of the number of radicals shows that, although the nature of the spectrum depends on the concentration of ethyl mercaptan, the total radical yield remains constant this suggests that the protective effect of the additive is due to a competition between electron scavenging by the additive and recombination with cations in the matrix, leading to scission of the polymer chain. The mechanism... 

It is beyond the scope of the present work to discuss the different options for the analytical methods. We only present one example here, showing what can be achieved with modern instrumental analysis. Fig. 4.15 shows a NMR-spectrum of a formaldehyde + water + methanol mixture taken with an online technique with a 400 MHz NMR spectrometer. Signals from a large number of different species can be resolved. Obviously, the band assignment is non-trivial for such complex mixtures and special techniques, such as two dimensional NMR, have to be applied. One of the most attractive features of NMR spectroscopy compared with other spectroscopic methods is that the quantitative evaluation of spectra such as that shown in Fig. 4.15 can be achieved without calibration, as the area below the peaks is directly proportional to the number of the different nudei in the solution if the NMR experiment is carried out properly. 

For material analysis a frequency analysis of emitted X-rays is evaluated. Since every element has its characteristic X-ray spectrum, the identification of the characteristic signal gives information about the chemical composition. Using an adequate standard, a quantitative evaluation is possible. The X-rays can also be used to create a map of the specimen which represents the elemental distribution. 

A technique that leads to quantitative data for the determination of the volume-fraction crystallinity is the infrared analysis. As an example, in Fig. 5.84 one can see the two areas in the IR spectrum of polyethylene where amorphous and crystalline samples are largely different (frequencies A and C). The equation in the upper right-hand comer permits now a quantitative evaluation, as is documented in Fig. 5.85 for... 

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