Derivation of system suitability test limits from a robustness test on an LC assay with complex antibiotic samples

A System Suitability Test (SST) is a test to verify the adequate working of the equipment used for analytical measurements. In pharmaceutical analysis, SSTs are performed at least at the beginning of a series of routine analyses. The most generally applied SST considers the precision of the analysis, i.e. the repeatability standard deviation must not exceed a predefined value. Additionally, a SST can also consider responses indicative for the quality of the technique used, e.g. resolutions between peaks or peak asymmetry in high performance liquid chromatography. The system is then only declared suitable if the response is within given limits. However, it is not always evident how to define the SST limits to be fulfilled for a newly developed method. Robustness tests have been proposed as a starting point in a strategy to deduce these limits. Here, it is examined how such a strategy can be applied for complex samples of microbial origin.