Normalizing the peak areas

Area Normalization (Raw Area Normalization). The peak areas of each peak are summed each peak area is then expressed as a percentage of the total ... 

The refractive index detector, in general, is a choice of last resort and is used for those applications where, for one reason or another, all other detectors are inappropriate or impractical. However, the detector has one particular area of application for which it is unique and that is in the separation and analysis of polymers. In general, for those polymers that contain more than six monomer units, the refractive index is directly proportional to the concentration of the polymer and is practically independent of the molecular weight. Thus, a quantitative analysis of a polymer mixture can be obtained by the simple normalization of the peak areas in the chromatogram, there being no need for the use of individual response factors. Some typical specifications for the refractive index detector are as follows ... 

There are two basic methods used in quantitative analysis one uses a reference standard with which the peak areas (peak heights) of the other solutes in the sample are compared the other is a normalization procedure where the area (height) of any one peak is expressed as a percentage of the total area (heights) of all the peaks. There are certain circumstances where each method is advantageous, and providing they are used carefully and appropriately all give approximately the same accuracy and precision. 

Table 9.11 shows the effect of this concentration on the responses of the other pesticides. In every instance the peak height was increased while the peak area remained constant. All of the columns used for this study were aged by repeated sample injections, but had not deteriorated to the point where they would normally be replaced. No values are included in Table 9.11 where the chromatographic system was not suitable for the pesticide concerned. 

FIGURE 1 GC-MS/MS monitoring chromatogram. The upper window depicts the internal standard (13C muramic acid) and the lower natural (12C) muramic acid isolated from dust. The peak areas in the two separate windows are normalized relative to the highest peak in that window. Medical samples appear similar... 

For quantitative analysis by electrophoresis, normalized peak areas are required. The normalized peak area is the measured peak area divided by the migration time. In chromatography, each analyte passes through the detector at the same rate, so peak area is proportional to the quantity of analyte. In electrophoresis, analytes with different apparent mobilities pass through the detector at different rates. The higher the apparent mobility, the shorter the migration time and the less time the analyte spends in the detector. To correct lor time spent in the detector, divide the peak area for each analyte by its migration time. 

Based on the method of internal normalization of peak areas, the percentage composition (less the diethyl ether solvent shown as the initial large component in Figures 1 and 2) of odor concentrates was estimated. The average composition of samples of odor isolates from individual preparations as well as from several different preparations of the same type—i.e., concurrent or noncurrent—was determined on the basis of all preparations which could be compared on a fair analytical basis (same gas chromatographic detector, column, and conditions). These results were then combined (traps plus distillate) to provide the rough estimations shown in Table IV. These data represent the best estimation of the composition of the total volatile odor concentrates from each processing method studied. 

The gas chromatographic method was tested in the presence of several ions normally found in environmental samples. In Table 15.22 the peak area of nitrobenzene produced from the standard solution containing... 

Experiment 3. Matrix Factor (MF) Test Extract six blanks from six different lots. Spike appropriate and same amount of analyte and IS into the postprocessed extract and neat sample, respectively. MF is the ratio of the peak area of the analyte in extract vs. neat sample. For stable labeled IS, the response can be normalized and peak area ratio (instrument response) can be used for MF calculation. For analog IS, the matrix factor must be calculated individually for analyte and IS. The recommended concentration for MF test is at medium QC level. 

Also, because of the additional substances present in adulterated samples, the peak area normalization method is applied only to those peaks due to heroin processing, including opium alkaloids, if present. 

The values represent the average and standard deviations for the areas under the specified m/e TPD feature normalized by the area under the ml e = 34 peak obtained in six independent measurements. b The peak areas were determined by fitting the TPD curves using a combination of a Gaussian and a Lorentzian. Fits to the formulas for first and second order desorption kinetics were also attempted but did not provide significantly better statistical results. 

Splitting of the —CHBr2 group in 1,1,2-tribromoethane. The Ha absorption is affected by the three combinations of Hb spins. When the Hb spins reinforce the external field, the Ha absorption occurs at a lower field. When the Hb spins oppose the external field, the Ha absorption occurs at a higher field. Two permutations, where the Hb proton spins cancel each other, allow Ha to absorb at its normal position. The peak area ratios are 1 2 1. 

Values for M were calculated using the PAG peak areas determined for several irradiated films as shown in Table I. The area of the PAG peak in each chromatogram was normalized to the area of the internal standard benzene peak and corrected by subtracting the normalized area of the background peak that was determined from the chromatogram of the film exposed to 418 mJ/cm . The PAG concentration M is proportional to the peak area and was normalized by setting the area of the peak for the unexposed film to 1.0. Figure 5 shows a plot of log M versus dose. The solid line is a least-squares fit to the data and G was determined from the slope of this line to be 0.013 (mJ/cm ) . ... 

Figure 1. Tcansmissiun FTlk results on the mixed monolayers spread on pure water with varying monolayer composition (stearic acid streaiyl alcohol) (a) and the peak area of the carbonyl band at various composition (b). The peak areas were normalized with respect to that of pure straric acid case (100 0).

A further quantitative measure, normalization, is sometimes utilized to determine the proportion of one or more components in a mixture. This involves calculating the ratio of the individual component peak area to the sum of the areas of all component peaks in the chromatogram. It assumes that all the components have identical response factors to the detector. This is a reasonable assumption when all the components of the mixture are chemically similar. When structurally dissimilar components are analyzed, a response factor correction should be used by measuring the peak area for a known quantity of pure material and calculating the respective response factor (F) from ... 

Again, the peaks must be paired based on their retention times, which must be equal or within a small interval. For a perfect fit, rel. (51) gives a factor F = 100%, and no match gives F = 0%. The peak areas in rel. (51) can be replaced by normalized peak areas, where the normalization is done for each chromatogram by an internal standard or by the total peak area. 

The absolute peak areas in rel. (52a) may be replaced by the peak areas normalized by an internal standard, or by the sum of all peak areas, or by the concentrations of the corresponding compounds 1, 2, 3,...n, (if these concentrations are known). 

Certain evaluation methods were examined based on the quantification processes. These can be divided into three groups, employing only the values of peak normalization (PN). The effect of the use of IS and certain evaluation methods, such as correction of peak area (normalization), was calculated by dividing the related peak area into on which the precision was examined. These can be divided into three groups a) employing only the area values of PN (PN no IS), b) computing the ratio values (IS no PN), and c) using the area values of peak normalized IS and ENX (IS and PN). The precision of the peak areas was calculated as shown in Table 1. 

We should know that the peak height is sensitive to instrument resolution. The peak area measurement under a vibration band shows much less instrumentation dependence. The peak area represents the integrated intensity of the vibration band and is proportional to the square of the change in dipole moment with respect to the normal coordinate as Equation 9.20. 

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