A new analytical method uses rubidium chloride density-gradient equilibrium analytical ultracentrifugation to resolve and quantify dual-AAV gene therapy vector capsids. The study reports high-resolution separation of two highly similar full capsid populations and accurate quantification. For dual-vector AAV manufacturing—where capsid composition consistency can influence potency and dosing accuracy—this provides a potentially valuable quality-control tool. It can also support comparability assessments across production lots and process changes. Regulatory-facing CMC teams may view the approach as an additional option to strengthen characterization beyond conventional assays.