System Suitability Test
A system suitability test is a means to assess the validity of HPLC results by ensuring that a series of criteria are met.
For example, if the column performance deteriorates, peaks become distorted and their heights and areas change; hence the calibration becomes invalid. So by setting a minimum peak efficiency (N) (or a minimum asymmetry, or tailing factor, or width at half height), then should the column devlop a void during an overnight run, the results will be automatically rejected once the peak width exceeds the prescribed limits.
Other criteria which can be monitored include
Resolution (useful if an unknown elutes overlapping the peak of interest),
Retention time (indicating a change in flow rate or a change in separation conditions such as temperature or %B), or Amount (if masuring components in a known concentration range) or