System suitability in bioanalytical LC/MS/MS

System suitability is widely recognized as a critical component of bioanalysis. This paper discusses a generic system suitability test that monitors instrument performance throughout a run when used for liquid chromatography tandem mass spectrometry (LC/MS/MS) in bioanalysis. This system suitability process is designed to ensure that the LC/MS/MS system is performing in a manner that leads to the production of accurate and reproducible data that can be submitted with confidence to regulatory agencies. This process contains tests for signal stability, carryover, and instrument response. This approach is integrated throughout an analytical run and has been used in the analysis of over 25,000 batches of clinical samples. Two case studies are presented in which quality control samples and standards meet all acceptance criteria (based on Standard Operating Procedures and the Food and Drug Administration's recommendations for bioanalytical method validation) but failed the proposed system suitability test, and thus were rejected. In these case studies, the concentrations of a significant number of clinical samples (over 35%) were affected, resulting in changes of more than 15% when the samples were reanalyzed. These data indicate that the poor performance of an LC/MS/MS system could adversely affect the calculated concentrations of unknown samples even though the results for quality control samples appear to be acceptable.