Peak area calculation methods

Gaussian curves are fitted to the data [28], and a peak area calculation program employed to integrate the area under each peak. This method is used to determine the evolution of peak area with time. The value of the extent of reaction, a, at a time t for any given Bragg reflection (hkl) is calculated using... 

Both lead and mercury speciation has been performed by Shum and coworkers [43]. Direct injection nebulization and an ion-pair separation with a microbore LC column were used with ICP-MS detection. A mobile phase of 20 80% v/v ace-tonitrile/water with 5 mM ammonium pentanesulfonate ion pairing reagent at pH 3.4 was used to separate inorganic lead, inorganic mercury, and three organomer-cury species. Detection limits, based on peak area calculations, were 0.2 pg of Pb for all the lead compounds and 7-18 pg of Hg for the mercury compounds. Spiked urine samples were analyzed to evaluate the performance of the method. 

Calculation Calculate the content of gamma-Cyclodextrin in the sample by the peak area percentage method using the following equation ... 

To 4 ml of sample add 0 400 ml of ethylbenzene and make up to 20 ml with acetone. Place 30 fA of this solution on to a column as described above and from the chromatogram calculate the camphor content of the sample using the peak area ratio method (see p. 878). 

Plasma lipids were extracted by the method of Folch et alP- after the addition of an internal standard. Standards of phytanic acid were similarly treated. Constituent fatty acids were then converted to their methyl esters and analysed by gas-liquid chromatography. The phytanic acid content was calculated by comparison of the ratio of the peak heights of phytanate to internal standard for the test with those for the standard. Phytanic acid was also calculated as a percentage of all fatty acids from C,4 to Cjo by comparison of peak areas calculated from the product of peak height and retention time. The results are shown in Table 8.1 where it can be seen that phytanic acid accounts for 50% of the total plasma fatty acids. 

Simpler methods have been reported for peak area calculation. Bowman uses a parabolic fit to the top half of the peak after subtraction of a carefully... 

Our calculations show that the systematic errors for the evaluation of the triangle height are lower then for the peak height and peak ar ea. It is to be noted that tangent method allows estimating of the latent peak in the overlapped signals when peak area and peak maximum determination is impossible. 

The aim of all the foregoing methods of factor analysis is to decompose a data-set into physically meaningful factors, for instance pure spectra from a HPLC-DAD data-set. After those factors have been obtained, quantitation should be possible by calculating the contribution of each factor in the rows of the data matrix. By ITTFA (see Section 34.2.6) for example, one estimates the elution profiles of each individual compound. However, for quantitation the peak areas have to be correlated to the concentration by a calibration step. This is particularly important when using a diode array detector because the response factors (absorptivity) may considerably vary with the compound considered. Some methods of factor analysis require the presence of a pure variable for each factor. In that case quantitation becomes straightforward and does not need a multivariate approach because full selectivity is available. 

Calculating the P/S ratio from the corresponding peak area ratios or by using one point calibration method leads to erroneous interpretations [54] because the P/S ratio depends on sample dilution. An accurate quantitation of FA is thus needed to evaluate this important parameter correctly. 

As a consequence of the development of extraction methods for STA based on mixed-mode SPE columns, as well as of the recent introduction of instruments for the automated sample preparation allowing efficient evaporation and derivatization of the extracts, full automation of STA methods based on GC-MS analysis is also available. It needs GC-MS instalments equipped with an HP PrepStation System. The samples directly injected by the PrepStation are analyzed by full scan GC-MS. Using macrocommands, peak identification and reporting of the results are also automated. Each ion of interest is automatically selected, retention time is calculated, and the peak area is determined. All data are checked for interference, peak selection, and baseline determination. 

This test uses the entire HPTC system with a specific chromatographic method and validated Cl8 column that should be <10 cm and commercially available. Validated means that the individual column was performance tested before being shipped and that a certified test chromatogram is included with each column. Injection precision testing is typically performed by replicate injections of a test standard (at least six replicates are suggested). One then calculates the peak area %RSD of a stable component in the test standard. Most LC... 

Now that we have a method by which to accurately acquire a digitized representation of the chromatogram, the data system must identify the individual peaks and calculate their area or height. 

Enantiomeric assay determinations are typically applied to characterize racemic mixtures using the normalized peak area (area%) calculation procedure. The selectivity solution is utilized to demonstrate the separation capability in the method and to allow peak identification. A suggested sample injection sequence can 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. ... 

To further confirm the ability of the reduced CE-SDS method to be used for determination of purity, percent corrected peak area (%HC, %LC, and %non-main) was calculated for each component with respect to the total corrected peak area. Eigure 8 presents the relationship between %HC, %LC, %non-main species, and injection time. 

The OPA reagent for HPLC is prepared according to the method of Benson and Hare (21). The fluorescence reaction is performed in a 55 C water bath. OPA reacts with the guanidino group of TTX presumably to form a fluorescent product, l-alkylthio-2-alkylisoindole (22, 23). TTX is monitored at 453 nm with 332-nm excitation. Peak areas are calculated by a data processing system of the analyzer. 

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