“Performance Qualification (PQ) is the process of demonstrating that an instrument consistently performs according to a specification appropriate for its routine use (5)”. Important here is the word ‘consistently’. The test frequency is much higher than for OQ. Another difference is that PQ should always be performed under conditions that are similar to routine sample analysis. For a chromatograph this means using the same column, the same analysis conditions and the same or similar test compounds.
PQ should be performed on a daily basis or whenever the instrument is used. The test frequency not only depends on the stability of the equipment but on everything in the system that may contribute to the analysis results. For a liquid chromatograph, this may be the chromatographic column or a detector’s lamp. The test criteria and frequency should be determined during the development and validation of the analytical method.
In practice, PQ can mean system suitability testing, where critical key system performance characteristics are measured and compared with documented, preset limits. For example, a well characterized standard can be injected 5 or 6 times and the standard deviation of amounts are then compared with a predefined value. If the limit of detection and/or quantitation are critical, the lamp’s intensity profile or the baseline boise should be tested. Table 6 gives a recommendation for a PQ example. [LIST=1]
- precision of the amounts
- precision of retention times
- resolution between two peaks
- peak width at half height or
- peak tailing
- limit of detection and limit of quantitation
- wavelength accuracy of a UV/Visible wavelength detector.
- every day
- every time the system is used
- before, between and after a series of runs