Qualitative and quantitative analysis using Raman scattering
First Claim
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1. A method for determining the composition of an unknown sample comprising:
- (a) producing a beam of photons which is substantially monochromatic and impinges on the unknown sample;
(b) collecting photons scattered by the unknown sample into a stream of scattered photons;
(c) resolving the photon stream into its component frequencies to form a Raman spectrum of the unknown sample;
(d) providing said unknown sample Raman spectrum to a computer;
(e) providing to the computer reference spectra obtained in the same manner as said unknown spectrum, where the reference spectra are of reference samples whose composition is known; and
,(f) identifying substances present in the unknown sample by comparing said unknown spectrum to the reference spectra, said comparison being accomplished by utilizing the computer and comprising the following steps;
(i) inspecting the unknown spectrum and selecting a plurality of separate spectral analysis regions;
(ii) determining a size characteristic associated with each of said spectral analysis regions of the unknown spectrum;
(iii) searching the reference spectra and choosing those reference spectra having in the selected spectral analysis regions features corresponding to those of the selected spectral analysis regions of the unknown spectrum and size characteristics substantially identical to those of the selected spectral analysis regions of the unknown spectrum;
(iv) if more than one reference spectrum is chosen, repeating steps (f)(i), (f)(ii), and (f)(iii), selecting additional spectral analysis regions, until only one reference spectrum is chosen, the substances present in said one chosen reference spectrum being present in the unknown samples;
(v) if no reference spectrum is chosen, establishing a number of working hypotheses, each hypothesis being that the unknown sample consists of a different combination of the reference samples which exhibited the spectra chosen to have features corresponding to those of the selected spectral regions of the unknown spectrum;
(vi) testing each working hypothesis by combining the spectra of the hypothesis to produce a single hypothetical spectrum and comparing it to the unknown spectrum;
(vii) discarding each working hypothesis which is not substantially identical to the unknown spectrum; and
,(viii) if more than one working hypothesis has not been discarded, repeating steps (f)(v) through (f)(viii), selecting additonal spectral analysis regions, until only one working hypothesis has not been discarded, the unknown sample composition then being that of said one remaining working hypothesis.
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Abstract
Methods and apparatus are provided for qualitative and quantitative analysis utilizing the Raman effect. Analyses are obtainable without exercise of human judgment or human interpretation. Analyses may be obtained on-line in the field or in a laboratory. A wide range of fluids and solids are capable of rapid routine analysis without major adjustment of equipment. An analysis is obtained by comparing a Raman spectrum of the unknown sample to Raman spectra of samples whose analysis is known. The known Raman spectra are stored in computing means in digital form and the comparison is accomplished by the computing means.
89 Citations
32 Claims
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1. A method for determining the composition of an unknown sample comprising:
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(a) producing a beam of photons which is substantially monochromatic and impinges on the unknown sample; (b) collecting photons scattered by the unknown sample into a stream of scattered photons; (c) resolving the photon stream into its component frequencies to form a Raman spectrum of the unknown sample; (d) providing said unknown sample Raman spectrum to a computer; (e) providing to the computer reference spectra obtained in the same manner as said unknown spectrum, where the reference spectra are of reference samples whose composition is known; and
,(f) identifying substances present in the unknown sample by comparing said unknown spectrum to the reference spectra, said comparison being accomplished by utilizing the computer and comprising the following steps; (i) inspecting the unknown spectrum and selecting a plurality of separate spectral analysis regions; (ii) determining a size characteristic associated with each of said spectral analysis regions of the unknown spectrum; (iii) searching the reference spectra and choosing those reference spectra having in the selected spectral analysis regions features corresponding to those of the selected spectral analysis regions of the unknown spectrum and size characteristics substantially identical to those of the selected spectral analysis regions of the unknown spectrum; (iv) if more than one reference spectrum is chosen, repeating steps (f)(i), (f)(ii), and (f)(iii), selecting additional spectral analysis regions, until only one reference spectrum is chosen, the substances present in said one chosen reference spectrum being present in the unknown samples; (v) if no reference spectrum is chosen, establishing a number of working hypotheses, each hypothesis being that the unknown sample consists of a different combination of the reference samples which exhibited the spectra chosen to have features corresponding to those of the selected spectral regions of the unknown spectrum; (vi) testing each working hypothesis by combining the spectra of the hypothesis to produce a single hypothetical spectrum and comparing it to the unknown spectrum; (vii) discarding each working hypothesis which is not substantially identical to the unknown spectrum; and
,(viii) if more than one working hypothesis has not been discarded, repeating steps (f)(v) through (f)(viii), selecting additonal spectral analysis regions, until only one working hypothesis has not been discarded, the unknown sample composition then being that of said one remaining working hypothesis. - View Dependent Claims (2, 3, 4, 5)
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6. A method for performing a quantitative analysis for preselected substances of an unknown sample comprising:
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(a) producing a beam of photons which is substantially monochromatic and impinges on the unknown sample; (b) collecting photons scattered by the unknown sample into a stream of scattered photons; (c) resolving the photon stream into its component frequencies to form a Raman spectrum of the unknown sample; (d) providing said unknown sample Raman spectrum to a computer; (e) providing to the computer reference spectra obtained in the same manner as said unknown spectrum, where the reference spectra are of reference samples whose quantitative composition is known and where each reference sample is comprised of at least one of said preselected substances; and
,(f) identifying substances present in the unknown sample by comparing said unknown spectrum to the reference spectra, said comparison being accomplished by utilizing the computer and comprising the following steps; (i) inspecting the reference spectra and selecting a plurality of separate spectral analysis regions; (ii) determining the areas of the selected regions for each reference spectrum and for the unknown spectrum; (iii) establishing a relationship between said reference spectra region areas and concentrations of said preselected substances in said reference samples; and
,(iv) determining the concentrations of said preselected substances in said unknown sample by applying the relationship established in step (f)(iii) to the unknown spectrum region areas. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. Apparatus for determining the composition of an unknown sample comprising:
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(a) means for producing a beam of photons which is substantially monochromatic and impinges on the unknown sample; (b) means for collecting photons scattered by the unknown sample into a stream of scattered photons; (c) means for resolving the photon stream into its component frequencies to form a Raman spectrum of the unknown sample; (d) means for converting said unknown sample Raman spectrum to digital form and transmitting said unknown spectrum to computing means; (e) said computing means, which contain reference spectra obtained in the same manner as said unknown spectrum, where the reference spectra are of reference samples whose composition is known; and
,(f) means within the computing means for identifying substances present in the unknown sample by comparing said unknown spectrum to the reference spectra, said computing means accomplishing said comparison by performing the following functions; (i) inspecting the unknown spectrum and selecting a plurality of separate spectral analysis regions; (ii) determining a size characteristic associated with each spectral analysis region of the unknown spectrum; (iii) searching the reference spectra and choosing those reference spectra having in the selected spectral analysis regions features corresponding to those of the selected spectral analysis regions of the unknown spectrum and size characteristics substantially identical to those of the selected spectral analysis regions of the unknown spectrum; (iv) if more than one reference spectrum is chosen, repeating functions (f)(i), (f)(ii), and (f)(iii), selecting additional regions, until only one reference spectrum is chosen, the substances present in said one chosen reference spectrum being present in the unknown sample; (v) if no reference spectrum is chosen, establishing a number of working hypothesis, each hypothesis being that the unknown sample consists of a different combination of the reference samples which exhibited the spectra chosen to have features corresponding to those of the selected regions of the unknown spectrum; (vi) testing each working hypothesis by combining the spectra of the hypothesis to produce a single hypothetical spectrum and comparing it to the unknown spectrum; (vii) discarding each working hypothesis which is not substantially identical to the unknown spectrum; and
,(viii) if more than one working hypothesis has not been discarded, repeating functions (f)(v) through (f)(viii), selecting additional regions, until only one working hypothesis has not been discarded, the unknown sample composition then being that of said one remaining working hypothesis. - View Dependent Claims (19, 20)
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21. Apparatus for performing a quantitative analysis for preselected substances of an unknown sample comprising:
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(a) means for producing a beam of photons which is substantially monochromatic and impinges on the unknown sample; (b) means for collecting photons scattered by the unknown sample into a stream of scattered photons; (c) means for resolving the photon stream into its component frequencies to form a Raman spectrum of the unknown sample; (d) means for converting said unknown sample Raman spectrum to digital form and transmitting said unknown spectrum to computing means; (e) said computer means, which contain reference spectra obtained in the same manner as said unknown spectrum, where the reference spectra are of reference samples whose quantitative composition is known and where each reference sample is comprised of at least one of said preselected substances; and
,(f) means within the computer for identifying substances present in the unknown sample by comparing said unknown spectrum to the reference spectra, said computer accomplishing said comparison by performing the following functions; (i) inspecting the reference spectra and selecting a plurality of separate spectral analysis regions; (ii) determining the areas of the selected regions for each reference spectrum and for the unknown spectrum; (iii) establishing a relationship between said reference spectra region areas and concentrations of said preselected substances in said reference sample; and (iv) determining the concentrations of said preselected substances in said unknown sample by applying the relationship established in function (f)(iii) to the unknown spectrum region areas. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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Specification