Assign one question to each quality attribute
RP-HPLC or UPLC can describe a chromatographic profile. MS or LC-MS can support molecular-mass identity. A suitable quantitative method addresses peptide content, while separate procedures may be needed for water, counter-ions, residual solvents, elemental impurities, bioburden or endotoxin when relevant.
Combine orthogonal evidence
Methods with different measurement principles reduce the risk that one technically correct result is mistaken for a complete quality conclusion. The method panel should be proportional to molecule complexity, supplied form, research sensitivity and first-lot risk.
- Identity method and supplied-form assumptions
- Purity method conditions and integration rules
- Content basis and quantitative method
- Water and counter-ion where material
- System suitability and reference materials
- Additional risk-based attributes
Require method suitability, not just instrument names
A laboratory having an HPLC or mass spectrometer does not prove that the procedure is suitable for the peptide. Ask how specificity, accuracy, precision, range and robustness were addressed for the decision being made.