Calculation of peak area

Calculation of peak area versus weighing for injection reproducibility... 

The most accurate measurements of peak areas are those obtained by means of electronic data reduction with integrators or computers. The vast majority of laboratories now have electronic or computer methods for determining peak areas. Two main features are required for electronic processing of chromatographic data accurate digitization of the analog signal and software. The software is required for the detection of peaks, correction for baseline drift, calculation of peak areas, retention times, and concentrations of components in the sample, and production of the final report.5... 

A first degree is equivalent to a linear response of interferences very often used for the exploitation of chromatographic data (calculation of peak area). The correction procedures of Allen (or Morton and Stub) are based on the same assumption. This solution is equivalent to the use of the second-derivative signal previously described, if we remember that a linear response gives a zero value for the second derivative. 

Figure 8.4 Calculation of peak areas by triangulation and direct peak measurement.

There are two main requirements for processing chromatographic data, accurate digitisation of the analogue detector signal and software to process the data. The software includes algorithms for detections of peaks, correction for base drift, calculation of peak areas and retention time, concentrations of components using stored detector response factors and production of the final analytical report. 

A symmetrical peak would have an asymmetry factor equal to 1.0. Most column manufacturers would consider a peak tailing factor of 0.9-1.2 to be acceptable. An unsymmetrical peak (Aj > 1.2 or A < 0.9) can have a detrimental effect on resolution and on the calculation of peak area for quantitative analysis. Steps can be taken to reduce peak tailing and these will be discussed further in Chapter 10. 

Foley, J.P. Equations for chromatographic peak modeling and calculation of peak area. Anal. Chem. 1987, 59, 1984-1987. 

Figure 5.5 Calculation of peak area using the Coveil method...

Figure 5.6 Calculation of peak area using extended background regions...

It is stiU possible to find incorrect expressions for the calculation of peak area uncertainty in the literature. The confusion arises because of a failure to appreciate that unlike single background counts where the variance of the count is numerically equal to the count itself, the variance of a peak background depends upon the number of background channels used. The offending expressions are variation of the form ... 

In analytical systems for instance, the objective is to identify components present in a small sample volume consequently these systems must be able to accommodate highly efficient columns containing very small particle diameter packings producing high column back pressures. Minimal volume in pipework, valves, and detector flow cells are required and a large emphasis is placed on data handling with automatic calculation of peak areas for concentration determination. There is no requirement for a fraction collector. 

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