Questions and Answers on System Suitability Tests (SST) - Part 3

During the ECA Live Online Training “System Suitability Tests (SST) and Troubleshooting for HPLC Methods” on 04 November 2025, a number of interesting and practice-oriented questions were raised by the participants. These questions were answered in writing by the speakers’ team after the event. To share some of the key insights with a broader audience, we have compiled a selection of these Q&As.

Below you will find Part 3 of the questions and answers, provided by Dr Gerd Jilge. Part 1 and Part 2 were published recently.

Part 3

3.1 – Are column inspections required, and how often should they be performed?
SST is the best way to check the suitability of the HPLC column for the respective analysis. Other column effects which might impact the analytical results should be identified during the validation experiments.

3.2 – In the presentation, you stated that an SST after HPLC service is not acceptable to check whether the system is performing as expected. Or did I misunderstand?
Up to now, an SST after service was accepted in most cases. However, there are increasing concerns regarding the suitability of the chromatographic system itself, because two different failures in the OQ might occur and might not be identified. These effects cannot be identified using an SST performed after service. Therefore, it is recommended to perform a test which covers all HPLC components at the end of the OQ to ensure the suitability of the system (e.g. using caffeine).

3.3 – Why is the %RSD evaluated at the 1% analyte concentration level in dissolution testing and not at 100% of the working concentration?
It depends on the type of release testing. In case of an immediate release higher concentration can be applied. However, in case of a sustained release testing other (lower) concentrations might be more suitable. The 1% level was an example only.

3.4 – Could you please provide some examples of system function tests (autotests) for UV spectroscopy and AAS analysis?
Autotests could mean the use of components that perform a part of the analysis automatically. In case of a UV spectrometer it could be an automated sampling unit or an automatic scan over the defined range of wave number. However, the most important suitability information can be provided using a suitable reference spectrum. Similarly, in case of AAS a part of the analytical measurement can be performed automatically.

3.5 – Should bracketing standards (intermediate standard injections) be evaluated throughout the sequence using the same %RSD criterion as described for system precision (n = 5 or 6)? In long sequences, should system precision be re-evaluated using 5 or 6 consecutive injections?
The SST should be defined before the sample analysis is started (SST could be performed with 5 as well as with 6 injections). Bracketing of the SST should not be performed because you need the suitability information before the start of the analysis.
In long sequences the easiest way of control is to include control standards during the whole sequence (e.g. checking the peak area of the control standard).