The FDA seeks an advanced quasi-elastic light scattering (QELS/DLS) detector for inline hydrodynamic radius measurement with an existing field-flow fractionation (FFF) system to characterize emerging pharmaceuticals and complex biologics. The detector must integrate with the current FFF hardware/software and MALS detectors, cover roughly 10–1000 nm, support orthogonal size validation, correlate DLS data with MALS molecular weight, and produce audit-trail-compliant regulatory-ready outputs. Deliverables include one QELS unit for FFF plus installation, instrument qualification, and training, with delivery/installation/qualification due within 120 days after contract award and training completed on installation day. Performance location is the FDA/CDER Office of Pharmaceutical Quality Research at 645 S Newstead Avenue, St. Louis, MO 63110. The period of performance is 12 months from system installation, and the order is firm-fixed-price with maintenance and technical support required.