Patent ID: 6633368
Filing Date: 2003-10-14
Classification: G01N

Abstract:
A method for determining the volume of particles in a liquid, the method comprising:(a) obtaining a suspension of particles in a liquid; (b) depositing said suspension into a container having at least one transparent window; (c) adding a fluorescent dye to said suspension in said container that does not substantially leak into said particles, wherein said fluorescent dye is able to absorb excitation light at wavelengths that are only weakly absorbed by said particles and emit fluorescence light at wavelengths that are only weakly absorbed by said particles; (d) illuminating said suspension with light, whereby the wavelength of said light is selected so that said light is being absorbed by said fluorescent dye but only weakly absorbed by said particles; (e) measuring a first intensity of fluorescent light that reemerges from said suspension in a first area of said suspension, wherein said first area contains no particles; (f) changing the thickness of said container in said first area by a known amount by pressing on said container from outside of said container and measuring a second intensity of fluorescent light that reemerges from said suspension in said first area; (g) measuring a third intensity of fluorescent light that reemerges from said suspension in a second area of said suspension, wherein said second area contains at least one particle; (h) measuring a fourth intensity of fluorescent light that reemerges from a third area of said suspension close to said at least one particle in said second area; and (i) determining the volume of said at least one particle based on said fluorescent light intensity values and said known change in thickness of said container.