A diazepam standard in clean solvent can respond differently from the same amount of diazepam in a seafood extract. Other compounds that reach the mass spectrometer at the same time can suppress or enhance ionization. The practical question is whether the sample cleanup makes that difference small enough to use solvent calibration.
Lou and colleagues used antibody-coated magnetic beads to isolate diazepam before UPLC–MS/MS. They compared calibration slopes from solvent and from five aquatic product extracts. The three fish matrices suppressed the signal slightly, while Pacific white shrimp and Chinese mitten crab enhanced it. The measured effects ranged from −3.04% to +6.27%.
Those slope comparisons support solvent calibration with the reported cleanup and matrices. A laboratory applying the method to a different tissue or changing the extraction can test the assumption directly by repeating the slope comparison in its own matrix.