Particle characterization

A method of determining a surface zeta potential, comprising:

• providing an electrical field in a sample, adjacent to the surface;
• illuminating a sample with a plurality of illuminating light beams;
• detecting light scattered from the illuminating light beams by particles in the sample along a plurality of detector paths, each of the detector paths corresponding with a different light detector, the detector paths corresponding with a plurality of measurement locations at different distances from the surface, and each detector path being at the same angle to an illuminating light beam, wherein the light detectors are arranged in a two dimensional array, and wherein the detector paths are arranged to respectively intersect with the illumination beams at a plurality of locations along the illumination beams, wherein each light detector corresponds to an optical fibre arranged to couple light from the respective detector path to the corresponding light detector, wherein each optical fibre is arranged to receive the scattered light from the detector path at a first end portion, wherein the first end portions of each optical fibre comprise a two dimensional array of fibres and wherein the first end portions of each fibre are oriented at different angles;
• and
• determining a surface zeta potential from the detected scattered light.

A method of determining particle size or particle size distribution, comprising;

• illuminating a sample with a plurality of illuminating light beams;
• detecting light scattered from the illuminating light beams by particles in the sample along a plurality of detector paths, each of the detector paths corresponding with a different light detector, each detector path being at the same angle to an illuminating light beam, so as to produce intensity signals for each detector path, and wherein the detector paths are arranged to respectively intersect with the illumination beams at a plurality of locations along the illumination beams, and wherein the detector paths are arranged in a two dimensional array, wherein each light detector corresponds to an optical fibre arranged to couple light from the respective detector path to the corresponding light detector, wherein each optical fibre is arranged to receive the scattered light from the detector path at a first end portion, wherein the first end portions of each optical fibre comprise a two dimensional array of fibres and wherein the first end portions of each fibre are oriented at different angles;
• performing an autocorrelation operation on the intensity signals to produce autocorrelation functions;
• identifying intensity signals and/or autocorrelation functions corresponding with contaminants and/or large particles;
• combining the autocorrelation functions that are not identified as corresponding with contaminants, to produce a total autocorrelation function;
• and
• determining the particle size or particle size distribution from the total autocorrelation function.

A method of determining particle size or particle size distribution, comprising;

• illuminating a sample with a plurality of illuminating light beams;
• detecting light scattered from the illuminating light beams by particles in the sample along a plurality of detector paths, each of the detector paths corresponding with a different light detector, wherein the light detectors are arranged in a two dimensional array, the detector paths corresponding with a plurality of measurement locations at different distances from the centre of a sample cell, each detector path being at the same angle to an illuminating light beam, and wherein the detector paths are arranged to respectively intersect with the illumination beams at a plurality of locations along the illumination beams, wherein each light detector corresponds to an optical fibre arranged to couple light from the respective detector path to the corresponding light detector, wherein each optical fibre is arranged to receive the scattered light from the detector path at a first end portion, wherein the first end portions of each optical fibre comprise a two dimensional array of fibres and wherein the first end portions of each fibre are oriented at different angles;
• excluding measurement locations that exhibit multiple scattering and/or insufficient scattering;
• and
• determining the particle size or particle size distribution from the measurement locations that are not excluded.