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Method for standardizing raman spectrometers to obtain stable and transferable calibrations

  • US 5,850,623 A
  • Filed: 10/09/1997
  • Issued: 12/15/1998
  • Est. Priority Date: 03/14/1997
  • Status: Expired due to Fees
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1. A method for producing a standard Raman spectrum from a sample using a particular Raman spectrometry apparatus or any of a plurality of similar Raman spectrometry apparatus, each said Raman spectrometry apparatus comprising a substantially monochromatic radiation source, excitation optical means, reference optical collection means, at least one sample optical collection means, a spectrograph, and a multi-channel array detector, said method comprising:

  • (a) using said spectrometry apparatus, simultaneously irradiating a reference material and at least one sample;

    (b) defining a standard energy dispersion characteristic, a standard Raman spectrum of said reference material, and a standard photometric response function;

    (c) simultaneously acquiring at more than one wavelength a convolved Raman spectrum of said reference material using a reference channel of said multi-channel array detector and a convolved Raman spectrum of said sample using a sample channel of said multi-channel array detector, said convolved spectra comprising a Raman-shift energy region included within said standard energy dispersion characteristic;

    (d) optionally identifying and removing noise spikes from each of the convolved Raman spectra of the reference material and the sample, thereby producing despiked convolved Raman spectra of said reference material and said sample;

    (e) irradiating each optical collection means and the spectrograph using a second radiation source and detecting the resulting signals with said detector, thereby producing a corresponding photometric reference spectrum for each optical collection means;

    (f) dividing each of the optionally despiked convolved Raman spectra of the reference material and the sample by said corresponding respective photometric reference spectrum, thereby producing compensated convolved Raman spectra of said reference material and said sample;

    (g) irradiating the spectrograph using a third radiation source and detecting resulting signals in each channel of the multi-channel detector, thereby producing a corresponding third radiation source spectrum for each detector channel;

    (h) from the corresponding third radiation source spectrum for each detector channel and said standard energy dispersion characteristic, constructing a corresponding wavelength,energy correlating equation for each detector channel;

    (i) applying the corresponding wavelength/energy correlating equation for each detector channel to each corresponding compensated convolved Raman spectrum of the reference material and the sample, thereby producing linearized convolved Raman spectra of said reference material and said sample;

    (j) optionally correcting the linearized convolved Raman spectrum of the reference material to remove background signals, thereby producing a corrected linearized convolved Raman spectrum of said reference material;

    (k) determining a convolution function from the standard Raman spectrum of the reference material and the optionally corrected linearized convolved Raman spectrum of said reference material;

    (l) applying the convolution function to adjust the linearized convolved Raman spectrum of the sample, thereby producing a deconvolved Raman spectrum of said sample; and

    (m) multiplying the deconvolved Raman spectrum of the sample by the standard photometric response function, thereby producing a standard Raman spectrum of said sample from a particular Raman spectrometry apparatus or from any of a plurality of similar Raman spectrometry apparatus.

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