Integration of signal areas

On autoradiographs, the width of a spot increases with the amount of radioactivity, which necessitates integration of signal areas for quantitar five determinations. 

From integration of signal areas, we can determine the relative numbers of hydrogens giving rise to each signal. 

A great advantage of C-NMR spectroscopy is that it is possible to count the number of types of carbon atoms in a molecule. There is one caution here, however. Because of certain complications, including the long relaxation times of C nuclei, it is generally not possible to determine the number of carbons of each type by integration of signal areas. 

In Fig. 16.1, Pq is the signal produced by saturated vapor, is the time of switch-over to pure carrier gas. At time tj the signal corresponds to the pressure P and the horizontally shaded portion of the curve is proportional to the quantity of adsorbate remaining in the column. By successive integrations of the area under the curve along the line SPF, the quantity adsorbed at various relative pressures can be calculated. 

In flow microcalorimetry a small sample is put into the cell of the calorimeter and the probe molecule passes through it in an appropriate solvent. Adsorption of the probe results in an increase in temperature and integration of the area under the signal gives the heat of adsorption [70]. This quantity can be used for the calculation of the reversible work of adhesion according to Eq. 13. The capabilities of the technique can be further increased if a HPLC detector is attached to... 

Exercise 9-28 The proton nmr spectrum of a compound of formula C6H1202, is shown in Figure 9-31. The signals are shown relative to TMS as the standard, and the stepped line is the integral of the area under the peaks from left to right. The infrared spectrum of the same compound shows a broad band at 3300 cm-1 and a strong band at 1700 cm-1. Deduce the structure of the compound and name it by the IUPAC system. 

NMR shift differences between groups which are enantiotopic by external comparison (i.e. in enantiomers) may likewise be induced by either chiral solvents 26 27) or chiral shift reagents 52). Integration of the areas of signals of enantiomers so shifted is used for the determination of enantiomeric excess, a topic which cannot be taken up here but has been discussed elsewhere 53). 

The thermal conversion is obtained through integration of the area comprised between the signal and the base line ... 

Now if the response index (r) is not unity, which will be the case for virtually all practical detectors, then the value of (r) should be taken into account in the expressions used to obtain quantitative results. Consider firstly the computer integration of the area. The area is calculated by summing all the signals from the detector over the period of the peak. Now, if (r l) then, from equation (2), the area that will incorporate the non-linearity will be... 

The stepped line is an electronic integration of the areas under the signal peaks, (a) List the chemical shift of each proton signal in ppm, and deduce, from the trace of the integrated areas, the identity of the protons that give rise to each line, (b) List the line positions in cps relative to tetramethylsilane expected at 100 Mcps. 

The area under a chromatographic peak, a spectroscopic band, or in thermal analysis is often directly proportional to the analyte concentration. Integration of signals is, therefore, important for quantitative data evaluation. 

In the NMR method, a deuterated chloroform solution of the polymer containing trimethylsilane internal standard is run on the proton NMR spectrometer. Integration of peak areas at delta 8 and 1-4 delta, respectively, gives a measure of signal strengths from aliphatic protons (methacrylate units) and aromatic protons (styrene). These areas can be used as a basis for calculating the methacrylate and styrene emit contents of the polymer. 

In the case of water pollution, the estimation of adsorption affinity of potential solid adsorbent toward the specific pollutant can be done using the so-called liquid microcalorimetry. The instruments used for this purpose are differential heat flow microcalorimeters modified to allow continuous stirring of liquid samples. The adsorbate is added to both sample and reference cells simultaneously using a programmable twin syringe pump, linked to the calorimeter. The heat evolved as a result of adsorption can be obtained by integration of the area under the calorimeter signal, for each particular injection (dose). The output of typical microcalorimetric experiment of this type is shown in Fig. 10.9. 

---