Disclosed in one general aspect is a particle interaction characterization instrument that comprises a flow cell for a liquid sample that includes suspended particles and a light source positioned to illuminate the suspended particles in the liquid sample fluid in the sample vessel. A first scattering detector is positioned to receive light from the light source that has been scattered by the particles suspended in sample fluid in the sample vessel at at least one predetermined scattering angle. An ultraviolet transmittance detector is positioned to receive a portion of the light from the source that passes through the suspended particles without being absorbed or scattered. Interaction analysis logic is responsive to both the scattering detector and the ultraviolet detector, and is operative to derive at least one interaction property for the suspended particles.