Plate Theory and Extensions - Retention Measurements on Close Eluting Peaks > Page 44

           and,                                                  (41)

Equation (41) is the Gaussian form of the elution curve equation and can be used as an alternative to the Poisson form in all applications of the Plate Theory.

Retention Measurements on Close Eluting Peaks

The retention data, are the most important measurements made in any chromatographic analysis. In addition to providing data for identification (using the capacity ratio or the separation ratio), retention times are also important in column design. It will be shown later that the column efficiency needed to ensure resolution of a pair of solutes can be calculated from the capacity ratio and the separation ratio of the two peaks. However, when the solutes are eluted close together, serious errors can arise in retention measurements. In addition, the error becomes particularly significant when the accurate calculation of the required retention and efficiency is particularly essential. The proximity of one peak to another distorts the apparent positions of the peak maxima in the combined envelope. Consequently, the apparent positions of the peak maxima are significantly different from their true positions when eluted individually. This effect is shown in Figure 10. The profiles of each peak are calculated employing the normal Error function (Gaussian) and are then superimposed by addition to provide the composite envelope.