Optimized LC-MS/MS methods for quantifying antibody–drug conjugate payloads in cell culture media containing phenol red

Aim: Phenol red is commonly used in cell culture media, but can be detrimental to bioanalysis of in vitro samples as it may impact instrument reliability. Many researchers do their final stage of culture in 'phenol red free' media, but in collaborative work this is not always feasible. Materials & methods: A comparison was made between typical extraction methods to reduce phenol red matrix interferences, including organic solvent precipitation and solid phase extraction. Results: The final method was demonstrated to be precise and accurate for the measurement of a target analyte by LC-MS/MS, and was applied to an in vitro ADC deconjugation study. Conclusion: This method allows for for continued bioanalytical support of in vitro models used in drug development.