Peak mis-identification occurs most often in degradation samples or those in which related substance levels are being measured. This is because the software is “calibrated” using a standard mixture with specific concentrations of each impurity. Most “real-life” samples contain impurities at very low levels so the retention time of their peaks will be slightly different to those generated by the standard mix.

Identification windows should be set widely enough to take into account this time variation with respect to concentration.