Analytical Ultracentrifuge – BeckmanCoulter Optima XL-A/XL-I

Optima XL-A/XL-I

BeckmanCoulter’s Optima XL series features this instrument with simultaneous absorbance and interference detection. This instrument has been our „workhorse“ from the very beginning in 2000. The distance covered by the rotor’s perimeter has surpassed Earth‘s distance to the sun years ago. Alike all centrifuges in our lab, the Optima XL runs at a maximum of 60,000 rpm, developing a field of 260,000-fold Earth’s gravity. Absorbance optics in the UV-Vis range allow for specific detection, whereas interference optics detect differences in refractive number which monitors any sedimenting (or floating) material. Though technical advances have been made in respect to optics and electronics, this instrument is still the most frequently used centrifuge in our lab.

Analytical Ultracentrifuge – Multiwavelength Absorbance Detection (4D-AUC)


Nanolytics Instruments‘ 4D-AUC adds a spectral dimension to absorbance detection – it detects complete UV-Vis spectra rather than absorbance data at a single wavelength. The detector is integrated into a BeckmanCoulter preparative centrifuge and controlled by Nanolytics Instruments‘ omega device and software.

Read more about this detector on the 4D-AUC page.

Analytical Ultracentrifuge – Advanced Interference Detection (AIDA)

AIDA periscope

An ultracentrifuge equipped with Nanolytics Instruments‘ Advanced Interference Detection Array (AIDA) features a considerably extended range of applicable concentrations. Its sensitivity is increased by a factor of five in respect to diluted solutions, compared to state-of-the-art detectors. It can also monitor highly concentrated solutions: a factor of more than 20 in comparison to standard interference detection is achieved.

Read more about this detector on the 4D-AUC page.

Analytical Ultracentrifuge – Turbidity detection


This instrument, also made by Nanolytics Instruments, is capable of measuring at variable rotor speed. Its typical application is to perform gravitational sweep experiments, covering a large range of angular velocities and, thus, particle sizes. As large particles cause turbidity, obstructing detection by absorbance and interference, turbidity detection at a fixed radius is applied to monitor particle sedimentation. This instrument focusses on applications in synthetic colloid characterization and material science.

Read more about this detector on the 4D-AUC page.

Analytical Ultracentrifugation – Accessories

Centrifuge cells

Our sample cells are applicable to any solvents, including acids, bases, and organic solvents. This is due to the fact that the centerpieces are made of titanium. Such cells are exclusively available from Nanolytics Instruments. In order to adjust the respective signal intensities we use centerpieces with four different optical path lengths: 1.5 mm, 3 mm, 12 mm, 20 mm. The cell windows are made of sapphire.

Cell alignment tool

High precision is required not only in instrumentation, but also in expermental handling. One of the most critical parameters is the correct alignment of sample cells within the rotor. Scratch marks on rotor and cell, traditionally used for azimuth alignment, cannot guarantee for the required precision. It has been shown that misalignment by several tenths of a degree can cause convection within the cell, resulting in measurement artifacts. We use the cell alignment tool made by Nanolytics Instruments for precise alignment of the cells within the rotor.

Light Scattering

Goniometer BI-200SM

For occasional, orthogonal measurements, we use a Light Scattering setup by Brookhaven Instruments. The Brookhaven BI-200SM is a multiangle goniometer for static and dynamic light scattering measurements. The usable angular range is 10° to 155°, depending on the quality of the sample. Motor driven, steps as small as 0.01° allow for extremely precise measurements.

The setup can be operated with two light sources by Toptica Photonics; 70 mW are emitted at wavelengths of 406 and 641 nm, respectively. Depending on whether red or blue light is applied, we use either a high-quality photon multiplier tube or an Avalanche photodiode array.

Both Static and Dynamic Light Scattering can be performed on this setup.

Size Exclusion Chromatography – SEC-MALLS

Postnova RI-Detector
Postnova-BIC MALLS-Detector

Our lab is equipped with a high-end SEC setup, featuring refractive index and multiangle light scattering detectors by Postnova. Both devices provide high precision with low baseline noise. In combination, they allow for conprehensive characterization of eluted species. Though this equipment is rarely used, as the lab has specialized more and more in AUC, we keep the equipment at hand for occasional measurements with an orthogonal method.

Complementary Measurements


Our lab is equipped with devices for measuring parameters required for the evaluation of AUC experiments, such as a densiometer and a refractometer. Partially, these are commercially available devices, some were custom built for our requirements. In specific, our refractometer is a unique, custom designed product by SLS Systemtechnik. The device features two light sources (405 and 635 nm), beam displacement is measured in a range from -0.2° to 2.2° at a maximum dn of 0.038°. The precision is 10-4°, yielding refractive numbers in six digit precision. This is an absolute measurement – beam displacement is amplified optically by means of a prism cascade and projected onto a CCD chip, yielding intensity spectra for analysis on the internal computer. This principle of measurement distinguishes the device from typical differential refractometers.