Peak Height Measurements

As peak height is inversely related to the peak width, then all parameters that can affect the peak width must be held constant.

Figure 34. Two Peaks Separated by Three Standard deviations

The capacity factor of the solute (k') must remain constant and, thus, the solvent composition held stable. The temperature must also be constant and a repeatable sample injection method must be used. Computer data acquisition gives a direct printout of the peak heights.To measure peak heights manually, the baseline is produced beneath the peak and the height between the extended baseline and the peak maximum measured. Peak heights measurement demand a minimum resolution and mathematical adjustments are not an alternative. In theory there should be no part of an adjacent peak situated under the maximum of the peak height to be measured. However, this is impossible due to the nature of the Gaussian function. In practice, the peaks should be separated sufficiently to allow a maximum error of 1.0% in peak height measurement. If the peaks are of equal height, then the criteria of 1% error is met by a separation of about three standard deviations. This situation is depicted in figure 34. It is seen peak overlap is very slight (in fact, if the height of the first peak is taken as unity, the height of the peak envelope at the point of peak maximum is still only 1.011).