Patent ID: 6774994
Filing Date: 2004-08-10
Classification: G01N

Abstract:
A method for determining the number density of monodisperse particles in solution comprising the steps ofA) Normalizing and calibrating a light scattering photometer, incorporating a fine beam of monochromatic light operating at a wavelength &lgr;0, to produce measurements at a plurality of scattering angles &thgr;i, of the corresponding Rayleigh ratios Rs (&thgr;i) of the light scattered into the corresponding direction &thgr;i from a contributing illuminated volume; B) Introducing a particle-containing solution into said normalized and calibrated photometer; C) Measuring the Rayleigh ratios Rs (&thgr;i) of said particle-containing solution; D) Subtracting from said measured Rayleigh ratios, Rs (&thgr;i), the corresponding Rayleigh ratios Rf (&thgr;i) of the suspending fluid at the same scattering angles &thgr;i to derive the excess Rayleigh ratios R(&thgr;i)=Rs (&thgr;i)âˆ’Rf (&thgr;i)at each said scattering angle &thgr;i; E) Selecting a model to describe the scattering particles; F) Deriving the effective size of said monodisperse particles in said particle-containing solution from said measured excess Rayleigh ratios at said plurality of scattering angles based on said particle model selected; G) Calculating the differential scattered intensity i(&thgr;i)of a single particle at each of said scattering angles from said derived effective size of said suspended monodisperse particles, the model selected of the individual scattering particles, and the refractive index of each said particle; and H) Calculating the number density N of said monodisperse particles in said contributing illuminated volume by multiplying a selected excess Rayleigh ratio at one measured angle &thgr;i by k2=(2 &pgr;n0/&lgr;0)2 and dividing said product by said calculated differential scattered intensity corresponding to said same angle to yield N=R(&thgr;i)k2/i(&thgr;i), where n0 is the refractive index of the solution and &lgr;0 is the vacuum wavelength of the incident light.