Normalized peak area

To highlight and explain the quantitative chemical differences between the pitches found in the two archaeological sites, a chemometric evaluation of the GC/MS data (normalized peak areas) by means of principal component analysis (PCA) was performed. The PCA scatter plot of the first two principal components (Figure 8.6) highlights that the samples from Pisa and Fayum are almost completely separated into two clusters and that samples from Fayum form a relatively compact cluster, while the Pisa samples are... 

Enantiomeric determinations are typically done according to a normalized peak area (area%) calculation procedure. A reporting threshold solution containing the lowest level to be... 

Depending on the type of calculation procedure, a set of SST-parameters is selected including system precision, reporting threshold, and system drift checks. If normalized peak area reporting is applied, the evaluation of the system precision is obviously not necessary. Frequently applied parameters and tentative limits comparable to HPLC methods are compiled in the Table 2. ... 

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. 

The measurement of odor intensity using OAVs is described by Grosch (1993, 1994). It requires the determination of the concentration of each odorant in the sample, and for those present in trace quantities, a stable isotope dilution assay must be used (Guth, 1997). This may make the determination of OAVs very tedious if many values are required. OS Vs are normalized peak areas from an odor chromatogram and represent a more realistic representation of the importance of the odors in a sample as perceived by the nose. Their determination is described by Acree (1997). 

Different polar organic solvents were tested as background electrolytes, and Af-methy 1 formamide was found to have the best properties with respect to both electrophoretic behaviour and high solubility of the interested compounds. The method was found to be precise (1.8% RSD for normalized peak areas), with good linearity and a low detection limit. 

Identity is a general requirement for dosage forms. When determining specificity for identity, the assay and related substances or the content uniformity methods can be used. Assay and content uniformity methods are quantitated by external reference standard. This identity test confirms that the correct active ingredient (s) is present and is present in correct ratio if multiple variants are available. The method could also be used for post-packaging analysis. The general requirements are that the sample and standard chromatograms should correspond in retention time and normalized peak area within 10%. 

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. 

An important feature of modern high-performance liquid chromatography (HPLC) is its excellent quantitation capability. HPLC can be used to quantify the major components in a purified sample, the components of a reaction mixture, and trace impurities in a complex sample matrix. The quantitation is based on the detector response with respect to the concentration or mass of the analyte. In order to perform the quantitation, a standard is usually needed to calibrate the instrument. The calibration techniques include an external standard method, an internal standard method, and a standard addition method. For cases in which a standard is not available, a method using normalized peak area can be used to estimate the relative amounts of small impurities in a purified sample. 

The normalized peak areas in this spectrum are proportional to the neutron cross sections (CS) for 77, D and Nb in a niobium hydride, with composition NbHxDy. The peaks are broadened by the fact that the nuclei have an intrinsic, characteristic spread of momentum Ap when they are hit by the neutron (the original purpose of this method was to deduce the width and shape of the distribution n(p) for 77 or I) in molecules or crystals [Brugger 1984]). 

Quantitative or semi-quantitative determination of analytes by SPME requires working within the linear dynamic range of the SPME fiber. If the linear dynamic range is exceeded, the extracted amount of analyte will not reflect the amount of analyte in the sample. Figure 2 shows the normalized peak areas for the headspace extractions of different amounts of powdered polyamide 6.6 [67]. The extraction time and temperature were 45 min and 80 °C. Under the given conditions, the dynamic range of the PDMS/DVB fiber was linear if the polyamide sample size was between 1 and 100 mg. For the... 

TABLE 5.11. Normalized Peak Areas of m/z Signals Used for Quantification of Acetaldehyde, Diacetyl, and Acetoin PFBOA Derivatives Calculated with Respect to LS.a... 

Nonaqueous capillary electrophoresis has been applied to the separation of basic drugs (316). Efficient, rapid, and versatile conditions were obtained with 20 mM ammonium acetate in acetonitrile-methanol-acetic acid (49 50 1). Baseline separations of 9 morphine analogs, 11 antihistamines, 11 antipsychotics, and 10 stimulants could each be obtained within 6 min. Migration times for individual components had Relative Standard Deviation between 0.8% and 3.5%. Using an internal reference, normalized peak areas were between 2.2% and 9.1%. The precision data was reported to be instrument dependent, since excellent results were obtained only when the instrument had precise evaporation- and temperature-control systems. 

Fig. 69 Changes of the normalized peak area of the bands at 725 cm 1 [( ) the out-of-plane bending of the imide ring], at 3060 cm 1 [( ) C H stretching vibrations of the aromatic ring], at 1750 cm [( ) imide and amide C=0 stretching vibration], and at 2220 cm" [( ) -C=N stretching vibration]. The experiment was performed at 812 K us-ing a total flow of 50 mLx min of compressed air. Applied Spectroscopy by T. Lippert [Ref. 281], COPYRIGHT (2001) by SOC FOR APPLIED SPECTROSCOPY. Reproduced with permission of SOC FOR APPLIED SPECTROSCOPY in the format Textbook via Copyright Clearance Center...

Modeling of Time Dependence. Simple Topological Description of the Overall Reaction. A better understanding of the reaction can be achieved by plotting the conversion of a specific structural unit. The conversion is proportional to the normalized peak area, and is plotted vs the normalized time necessary for the complete reaction [289, 301-305]. Similar plots are used in heterogeneous catalysis to study the rate-controlling step of a process [321]. In Fig. 70 top, a plot for the aromatic rings (3060 cm1) at temperatures of 783 K (V), 812 K (+) and 841 K ( ) is presented. In Fig. 70 bottom, the imide system (725 cm1) is plotted at the same temperatures (783 K A 812 K X and 841 K A). 

In a study [6] of the dissolution of amorphous silica gels in aqueous alkali metal hydroxides, the rate of dissolution was found to depend on the cation used in the dissolution reaction. A maximum in dissolution rate was found for potassium hydroxide solutions, whereas both intrinsically smaller and larger cations (lithium-sodium and rubidium-cesium) showed slower dissolution rates, as can be concluded from the concentration of dissolved silicate species (normalized peak areas) as a function of alkali metal cation (Figure 45.2). This result is contradictory to the expectation that a monotonic increase or decrease in dissolution rate is to be observed for the different cations used. One major effect that occurs at the high pH values of this study is that the majority of silanol... 

The calorific values (heats of combustion) were also assigned from these oxidative profiles by comparing the total normalized peak areas, given by the peak analysis routine of the TAiDS, to that of a high volatile bittiminous coal of known calorific value (Alfa Resources 108F Coal Standard). The calorific values were then calculated by the relationship... 

However, the application of statistical techniques to urine head-space volatile profiles obtained from two cows over two complete cycles discriminated reproducibly between profiles obtained at different stages of the estrous cycle (Morgans, 1984). Data from 49 normalized peak areas from 83 chromatograms on canonical variates analysis (MacFie et al.,... 

Quantification is simple if the atoms are homogeneously distributed with depth since the intensity of each XPS peak is then directly related to the abundance of that particular element at the specimen surface. The peak intensity will usually be reported as a peak area and this will be normalized using atomic sensitivity factors (the intensity of the photoelectron transition of interest, I, is related to the concentration of that element within the XPS analysis volume, and the sensitivity factor, S, in the following way F= concentrationxS). Such atomic sensitivity factors are a function of the basic physical parameters, such as the relative photoelectron cross-sections of the different elements, electron attenuation lengths, and instrumental parameters, such as analyzer transmission functions, of the XPS experiment. The ratio of normalized peak area to the sum of normalized peak areas for the major peaks of all elements detected in the spectrum provides an analysis as an atomic fraction (or when multiplied by 100, atomic %). 

Quantitative analysis usually requires the use of standards and/or certified reference materials (CRMs), the selection of an appropriate elemental optical emission line, and, in most cases, the selection of a normalization line, used as an IS. Calibration curves are then constructed using the normalized peak area versus concentration, as previously described for calibration using an IS. When there is a dominant matrix component for which the concentration will remain approximately constant across the calibration set, it is best to use an emission line from that matrix element for normalization. This approach helps minimize effects due to changes in plasma conditions caused by shot-to-shot fluctuations in laser intensity. Alternatively, chemometric correlation analysis of the entire observed spectrum with the concentration of the analyte can be used to construct calibration curves automatically. In general, RSDs of 5%-10% are readily achievable. To improve quantitation, sample preparation methods such as pressing pellets may improve results for soils and sediments and fusion with salts to convert the sample into a glass bead can eliminate matrix effects. Fusion was discussed in Chapter 1 and is used extensively in XRF analysis (Chapter 8). 

Applications of CIEF for the separation of isoforms of transferrin have been reported by several groups. - Transferrin contains different number of sialic acid residues, with an additional -1 charge added per residue. Also, transferrin bound to different amount of iron atoms has been separated by CIEF. Glycoforms of recombinant tissue-type plasminogen activator (rtPA) is another sialic acid containing protein which has been the subject of analysis by CIEF. - " A rapid (<10 min) one-step method was developed using a coated capillary, HPMC, and urea in a mixture of pH 3-10 and pH 5-8 ampholytes. Ten species could be detected. Intra-assay precision was less than 5% for peak migration times and 10% for normalized peak areas. 

For quantitative analysis, use normalized peak area peak area migration time... 

From Figure 23-15, estimate the concentration of nitrate in the aquarium water. Aquarium water was diluted from 1 mL to 100 mL, and the final solution contains the same 10 ppm of internal standard IO4 as in the standard mixture. For an estimate, use peak height instead of peak area. There is no need to use normalized peak area = peak area/migration time because migration times are nearly the same in both electropherograms. 

Experimental (overall) peak areas divided by the corresponding elemental sensitivity factors and expressed as a percentage of the summed normalized peak areas. 

Again, calculate the peak area of the indium melt and include the onset temperature in the calculation (Fig. 4). Observe that the limits of the calculation are set on the flat portion of the baseline before and after the melting peak. Use the onset temperature as the melting point of indium and use the normalized peak area (AB) as the enthalpy value for indium. Indium is the purest material available for calibration of a DSC and should always be... 

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