Bioanalytical method optimization for simultaneous quantification of structurally related probe drugs in a phenotyping cocktail using liquid chromatography‐tandem mass spectrometry

The physicochemical diversity of the structurally related aromatic probe drugs, used together in a drug cocktail to assess metabolic and transport phenotypes, require optimized analytical procedures for simultaneous quantification. The analytical conditions can greatly influence the analyte selectivity, retention, stability, and ultimately the robustness of the method. The aim of this study was to assess the selectivity of the structurally related ionizable analytes between the commonly used C18 column chemistry and an alternative biphenyl column chemistry as well as the influence of changes in the analytical conditions on method robustness using liquid chromatography‐tandem mass spectrometry. A repeated measure two‐factor analysis of variance with Geisser‐Greenhouse correction was used to determine statistical significance. The results showed that a biphenyl stationary phase in combination with methanol as the organic eluent, could provide improved resolution and analyte selectivity. Changes in analytical conditions caused statistically significant variation in the retention behavior, selectivity, column efficiency, and sensitivity of the analytes of interest The robustness experiment confirmed the importance of controlling analytical conditions to ensure the reproducibility and reliability of the quantitative method.