Defining Detection Parameters
Defining the Area for PPA  

When using Photodiode Array Detectors and recording 3D Fields, you may check the peak purity with the Peak Purity Index (PPI).

Define the most expressive area of you spectrum by means of the Peak Purity Start/End Wavelength parameters and limit the examination to this area only.

The detection limit becomes especially apparent with very small peaks. The influence (that is the noise, drift and limits of the measuring method) on the peak spectrum is strongly developed at the peak start and peak end because, in these areas, the concentration of the peak substance in the flow cell is very low. Set the Peak Purity Threshold parameter to reduce the influence on the PPI and the match factor and, thus, to prevent that contaminated substances are indicated falsely. The PP threshold value defines the percentage of the peak height starting as of which the spectra will be considered for the respective purity examination.

If you work close to the detection limit, use higher PP threshold values to reduce the influence of the detection limit on the purity examinations. If you are mainly interested in the purity of large peaks, use lower PP threshold values to examine the purity over the largest possible area of the peaks.