Rayleigh interference optics is used as the second standard detector system in Analytical Ultracentrifugation, detecting all sedimenting material, not only absorbant species. Interference detection is mandatory for non-chromophoric solutes or systems with chromophoric solvents, not permitting absorbance measurements. While the dynamic range of interference detection is intrinsically high, a superior data quality is ensured by high scan speeds, systematic rather than statistical noise, and high resolution.
Though some of these advantages have been neutralized by the development of an advanced absorbance detector, interference optics remain an important tool for the cases given above or as a supplemental detection system. Aida represents the most advanced interference detector to date, extending both the minimum and maximum tractable solute concentrations.
Aida is capable of recording steep fringe gradients generated by highly concentrated protein solutions. In contrast, the Optima XL-I ultracentrifuge is not able to resolve such steep interference profiles. In practice, the XL-I system is observed to fail at recording fringe gradients of antibodies at 100 g/L measured in cells of the lowest tractable optical pathlength of 1.5 mm. Similarly, the resolution of interference data is significantly increased allowing for the analysis of diluted solutions down to a range of 0.01–0.03 g/L, at which interference data quality of the Optima XL-I is too low for an accurate quantitative analysis.
AIDA has been in operation for years at Nanolytics' contract service lab in Potsdam. During this time, AIDA has provided excellent interference data for a variety of system. As examples for extreme systems, we show data for