| Assay |
Purpose |
| Field flow fractionation multiangle light scattering (FFF-MALS) |
Determine particle number and aggregation state |
| Atomic force microscopy (AFM) |
Determine particle number and aggregation state |
| Transmission electron microscopy (TEM) |
Determine particle number |
| Size exclusion chromatography multi - angle light scattering (SEC-MALS) |
Determine particle number and aggregation state |
| TCID, FFA, plaque, or other assays |
Determine proportion of defective particles based on the difference between total particles and infectious particles |
| Polymerase chain reaction (PCR) |
Determine proportion of nucleic acid containing particles |
| Density gradient centrifugation |
Determine proportion of defective particles based on relative densities of particle populations |
| Analytical ultracentrifugation (AUC) |
Determine proportion of defective and aggregated particles based on hydrodynamic properties of particle populations |
| Capillary electrophoresis (CE) |
Determine proportion of defective and aggregated particles based on particle mass and charge |
| Reversed-phase HPLC (RPHPLC) |
Determine proportion of defective and aggregated particles based on hydrophobic interaction properties |
| Ion-exchange chromatography (IEC) |
Determine proportion of defective and aggregated particles based on charge state of the particles |
| Size exclusion chromatography (SEC) |
Determine proportion of defective and aggregated particles based on hydrodynamic sieving properties of particle populations |
| SDS-PAGE (or equivalent) |
Determine composition of proteins contained in preparation based on polypeptide chain sizes |
| Western blot |
Determine composition of immunoreactive proteins contained in preparation |
| Process residuals (BSA, benzonase, polysorbate, etc.) |
Quantify process-related impurities |
