Automation of Ingredient-Specific Particle Sizing Employing Raman Chemical Imaging

Abstract

A system and method for determining at least one geometric property of a particle in a sample. A sample is irradiated to thereby generate Raman scattered photons. These photons are collected to generate a Raman chemical image. A first threshold is applied wherein the first threshold is such that all particles in the sample are detected. A particle in the sample is selected and a second threshold is applied so that at least one geometric property of the selected particle can be determined. At least one spectrum representative of the selected particle is analyzed to determine whether or not it is a particle of interest. The step of determining a second threshold may be iterative and automated via software so that candidate second thresholds are applied until a satisfactory result is achieved.

What is claimed is: 
     
         1 . A method comprising:
 (a) irradiating a sample comprising at least one unknown particle to thereby produce Raman scattered photons;   (b) collecting said Raman scattered photons to thereby generate a Raman chemical image representative of said sample;   (c) applying a first threshold to said Raman chemical image wherein said first threshold is such that all particles in said sample are detected;   (d) selecting one of said particles detected as a result of applying said first threshold;   (e) applying a second threshold to said Raman chemical image to thereby determine at least one geometric property of said selected particle, wherein said second threshold is unique to said selected particle such that said at least one geometric property can be determined;   (f) analyzing at least one spectrum representative of said selected particle to thereby classify the selected particle as at least one of: a particle of interest and not a particle of interest.   
     
     
         2 . The method of  claim 1  wherein said analyzing comprises comparing at least one spectrum representative of said selected particle to at least one reference spectrum representative of a particle of interest. 
     
     
         3 . The method of  claim 2  further comprising the steps of:
 (g) if said comparing results in a match between said spectrum representative of said selected particle and said reference spectrum representative of said particle of interest, identifying the selected particle as a particle of interest; and 
 (h) if said comparing does not result in a match between said spectrum representative of said selected particle and said reference spectrum representative of said particle of interest, identifying the selected particle as not a particle of interest. 
 
     
     
         4 . The method of  claim 1  further comprising repeating steps (d)-(f) for at least one other unknown particle present in said sample. 
     
     
         5 . The method of  claim 1  wherein said at least one geometric property comprises the size of said selected particle. 
     
     
         6 . The method of  claim 1  wherein said at least one geometric property of said selected particle is selected from the group consisting of: an area, a perimeter, a feret diameter, a maximum chord length, a shape factor, an aspect ratio, and combinations thereof. 
     
     
         7 . The method of  claim 1  wherein said at least one geometric property of said selected particle is characteristic of particle size distribution. 
     
     
         8 . The method of  claim 1  further comprising fusing said Raman chemical image with a brightfield image representative of said sample to thereby generate a fused image representative of said sample. 
     
     
         9 . The method of  claim 8  further comprising analyzing said fused image to thereby determine at least one geometric property of at least one unknown particle in said sample. 
     
     
         10 . The method of  claim 1  wherein said second threshold comprises a fraction of the peak intensity of the Raman spectrum corresponding to said selected particle. 
     
     
         11 . The method of  claim 10  wherein said fraction comprises one half. 
     
     
         12 . The method of  claim 1  wherein said second threshold comprises the peak intensity of at least one Raman spectrum corresponding to at least one edge of the selected particle. 
     
     
         13 . The method of  claim 1  wherein said second threshold is determined by averaging the peak intensities of two or more Raman spectra corresponding to at least one edge of said selected particle. 
     
     
         14 . The method of  claim 1  wherein said second threshold is determining by a method comprising:
 (a) applying a candidate second threshold to said Raman chemical image; 
 (b) assessing the effectiveness of said candidate second threshold; and
 (i) if, based on said assessment, said candidate second threshold is effective, identifying said candidate second threshold as a second threshold unique to said selected particle such that said at least one geometric property can be determined, and 
 (ii) if, based on said assessment, said candidate second threshold is not effective, repeating steps (a)-(b) for at least one other candidate second threshold. 
 
 
     
     
         15 . The method of  claim 14  wherein a candidate second threshold is determined to be effective when the intensity of the selected particle is five standard deviations above the average background. 
     
     
         16 . The method of  claim 1  further comprising applying a chemometric technique to said Raman chemical image. 
     
     
         17 . The method of  claim 16  wherein said chemometric technique is selected from the group consisting of: cluster analysis, principal component analysis (PCA), Cosine Correlation Analysis (CCA), Euclidian distance analysis (EDA), multivariate curve resolution (MCR), band t. entropy method (BTEM), Mahalanobis distance (MD), adaptive subspace detector (ASD), multivariate curve resolution (MCR), and combinations thereof. 
     
     
         18 . The method of  claim 1  wherein said method is automated via software. 
     
     
         19 . The method of  claim 14  wherein said second threshold determination method is automated via software. 
     
     
         20 . A method comprising:
 (a) irradiating a sample comprising at least one unknown particle of interest to thereby produce interacted photons wherein said interacted photons are selected from the group consisting of: Raman scattered by said sample, reflected by said sample, emitted by said sample, absorbed by said sample, and combinations thereof;   (b) collecting said interacted photons to thereby generate a chemical image representative of said sample;   (c) applying a first threshold to said chemical image wherein said first threshold is such that all particles in said sample are detected;   (d) selecting one of said particles detected as a result of applying said first threshold;   (e) applying a second threshold to said chemical image to thereby determine at least one geometric property of said selected particle, wherein said second threshold is unique to said selected particle such that said at least one geometric property can be determined;   (f) analyzing at least one spectrum representative of said selected particle to thereby classify the selected particle as at least one of: a particle of interest and not a particle of interest.