Abstract: An apparatus and method are disclosed for determining electrophoretic mobility using scattering light phase analysis comprising emitting a laser light along a path and transmitting a first portion of the laser light and reflecting a second portion of the laser light. The apparatus and method can also comprise deflecting one of the first and second portions of the laser in response to a drive signal, holding a sample to receive at least one of the first and second portions of the laser light under an electric field and output a composite light wave, outputting a photopulse signal based on the composite light wave, and measuring the electrophoretic mobility of the sample based on a phase shift analysis using cross-correlation of the photopulse signal with the drive signal.

Abstract: A single-particle optical sensor, which has high sensitivity and responds to relatively concentrated suspensions, uses a relatively narrow light beam to illuminate an optical sensing zone nonuniformly. The zone is smaller than the flow channel so that the sensor responds to only a fraction of the total number of particles flowing through the channel, detecting a statistically significant number of particles of any relevant diameter. Because different particle trajectories flow through different parts of the zone illuminated at different intensities, it is necessary to deconvolute the result. Two methods of deconvolution are used: modified matrix inversion or successive subtraction. Both methods use a few basis vectors measured empirically or computed from a theoretical model, and the remaining basis vectors are derived from these few. The sensor is compensated for turbidity. Several embodiments are disclosed employing light-extinction or light-scattering detection, or both.

Abstract: An apparatus and method are disclosed for determining electrophoretic mobility using scattering light phase analysis comprising emitting a laser light along a path and transmitting a first portion of the laser light and reflecting a second portion of the laser light. The apparatus and method can also comprise deflecting one of the first and second portions of the laser in response to a drive signal, holding a sample to receive at least one of the first and second portions of the laser light under an electric field and output a composite light wave, outputting a photopulse signal based on the composite light wave, and measuring the electrophoretic mobility of the sample based on a phase shift analysis using cross-correlation of the photopulse signal with the drive signal.

Abstract: A single-particle optical sensor, which has high sensitivity and responds to relatively concentrated suspensions, uses a relatively narrow light beam to illuminate an optical sensing zone nonuniformly. The zone is smaller than the flow channel so that the sensor responds to only a fraction of the total number of particles flowing through the channel, detecting a statistically significant number of particles of any relevant diameter. Because different particle trajectories flow through different parts of the zone illuminated at different intensities, it is necessary to deconvolute the result. Two methods of deconvolution are used: modified matrix inversion or successive subtraction. Both methods use a few basis vectors measured empirically or computed from a theoretical model, and the remaining basis vectors are derived from these few. The sensor is compensated for turbidity. Several embodiments are disclosed employing light-extinction or light-scattering detection, or both.