The Zetasizer Ultra uses the Dynamic Light Scattering (DLS) and the Electrophoretic Light Scattering (ELS) techniques to determine the particle size (from 1 nm to 10 μm) and the electrokinetic potential, the so-called Zeta potential, which can be used to determine the stability of the colloidal system. The Zetasizer Ultra is equipped with a He laser with a wavelength of 633 nm. The Non-Invasive Back-Scatter (NIBS) technique increases the sensitivity and versatility in the size determination. In addition to the back-scatter detector, operating at an angle of 173°, the instrument is equipped with an additional two detectors, a side-scatter 90°, and a forward-scatter 13°. This extension implements the Multi-Angle Dynamic Light Scattering (MADLS) technique. The MADLS allows the determination of the particle concentration, in a number of particles per volume, and further increases the sensitivity and resolution of measurements. The range of measurable concentrations varies, depending on the nature of the sample, from 1∙10¹³ to 1∙10⁸ particles/ml. The minimum concentration for optimal MADLS analysis is 1 mg/ml, depending on the nature of the sample, for NIBS analysis, the minimum concentration is 0.1 mg/ml. Also, a fluorescent filter is available for NIBS which allows the measurement of the fluorescent samples and a capillary cuvette cell with a minimum measurable volume of 3 μl. For the Zeta potential measurement, the minimum sample concentration is 1 mg/ml, and a disposable cuvette with a minimum volume of 700 μl is available.