After cell assembly, the AUC was accelerated to 5,000 rpm for 3 min to transfer the sample in the reservoir via capillaries to overlay the D2O column. Afterwards, the speed was increased to 55,000 rpm. Forty scans were taken with a time interval of 90 s and a radial step size of 50 μm to observe the full sedimentation of the sample. The selected wavelength range was 250–750 nm. In the prototype setup, we apply the spectrum acquired for an empty cell as a reference for the calculation of the absorption leading to a baseline offset of 0.05 OD (see Fig. 3i) After the experiment, while cleaning the cell, we saw some precipitate in the cell reservoir. Thus, not all particles were transferred to the sample column, but some big particles remained in the reservoir as they already must have completely sedimented upon speeding up the rotor to 5,000 rpm.
Fig. 3 Three-dimensional plots of the raw data from a band sedimentation experiment with β-carotene detected with the MWL detector. The axes are wavelength, absorbance and radial position. i Scan 1 (1.5 min); ii Scan 10 (15 min); iii Scan 18 (27 min); iv Scan 40 (60 min)