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Electrophoretic light scattering is based on dynamic light scattering. The frequency shift or phase shift of an incident laser beam depends on the dispersed particles mobility. In the case of ''dynamic light scattering'', Brownian motion causes particle motion. In the case of ''electrophoretic light scattering'', oscillating electric field performs the same function. This method is used for measuring electrophoretic mobility and then calculating zeta potential. Instruments to apply the method are commercially available from several manufacturers. The last set of calculations requires information on viscosity and dielectric permittivity of the dispersion medium. Appropriate electrophoresis theory is also required. Sample dilution is often necessary in order to eliminate particle interactions. ==Instrumentation of Electrophoretic light scattering== A laser beam passes through the electrophoresis cell, irradiates the particles dispersed in it, and is scattered by the particles. The scattered light is detected by a photo-multiplier after passing through two pinholes. There are two types of optical systems: heterodyne and fringe. Ware and Flygare 〔R. Ware and W.H. Flygare, J.Colloid Interface Sci. 39: 670 (1972).〕 developed a heterodyne-type ELS instrument, that was the first instrument of this type. In a fringe optics ELS instrument,〔J. Josefwiicz and F.R. Hallett, Appl. Opt. 14: 740 ( (1975).〕 a laser beam is divided into two beams. Those cross inside the electrophresis cell at a fixed angle to produce a fringe pattern. The scattered light from the particles, which migrates inside the fringe, is amplitude-modulated. The frequency shifts from both types of optics obey the same equations. The observed spectra resemble each other. Oka et al. developed an ELS instrument of heterodyne-type optics〔K. Oka, W. Otani, K. Kameyama, M. Kidai, and T. Takagi, Appl. Theor. Electrophor. 1: 273-278 (1990).〕 that is now available commercially. Its optics is shown in Fig. 3. A modulator is a translationally moving mirror. A frequency of reference light shifts by the movement. Scattered light from dispersed particle without electrophoretic movement is line broadened. That with electrophoretic movement is line broadened and Doppler shifted. The moving mirror moves to shorten optical pass length, then the frequency shift toward higher frequency. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Electrophoretic light scattering」の詳細全文を読む スポンサード リンク
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