| 摘要 |
A method and apparatus is disclosed for measurement of the Electrophoretic mobility of particles and molecules in solution. A sample of particles is placed in a cell containing two electrodes that apply an alternating electric field. A monochromatic light beam passes through the sample. Light scattered by the particles, along with the unscattered beam, is collected and collimated as it exits the cell. This beam is combined in free space with a phase modulated reference beam. The interference forms a frequency modulated speckle pattern, which is detected by a photodetector array. Each array element collects a narrow range of well-defined scattering angles. The signal from each is demodulated to extract the optical phase information providing a first-principle measurement of the Electrophoretic mobility of the scattering particles. Each detector element provides a simultaneous independent measurement. This inherent parallelism drastically increases the amount of information available in a given time. The resulting increased sensitivity extends the mobility measurement to particles below one nanometer, reduces the required concentration and electric field compared to previous methods. This minimizes damage to fragile samples, increases the electrode useful life, and reduces joule heating. Electrophoretic mobility is a critically important parameter for predicting the stability of nanoparticle suspensions and pharmaceutical formulations such as protein therapeutics. This invention enables reliable free-solution phase measurement of these samples. |
