Data Processing

Chromatographic data can be processed manually or by computer, consequently, both processes will be discussed and as the logic of the software is based on manual measurement techniques, the manual procedure will be considered first.

Introduction to Manual Measurement

The information required is, 1/ the retention time, 2/ the peak height, 3/ the peak width..

Figure 32. Peak Measurements

The retention time is used for peak identification and the peak height and peak width for quantitative evaluation. In the manual measurement of peak area, the peak area is taken as proportional to the product of the peak height and the peak width measured at the points of inflexion. This assumption is theoretically sound provided the peak is Gaussian or near Gaussian in shape.

A typical peak on which measurements might be made is shown in figure 32Measurements should be estimated to the nearest 0.2 mm (if necessary using a lens or loupe). If capacity ratios are used for identification, the chart speed (or flow rate) is adjusted so the distance between the injection point and the dead point is at least 2 cm. This ensures that measurement error will be no greater than 1 %(i.e. 0.02/2 x 100).