Method of creating standardized spectral libraries for enhanced library searching

• US 5,710,713 A
• Filed: 01/18/1996
• Issued: 01/20/1998
• Est. Priority Date: 03/20/1995
• Status: Expired due to Term

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Leugers, Mary A., Beebe, Kenneth R., LaPack, Mark A., Wright, Larry G., Blaser, Wayne W.
• Primary Examiner(s): Trammell, James P.
• Assistant Examiner(s): KEMPER, MELANIE A
• Application Number:
  US08/588,192
• Time in Patent Office: 733 Days
• Field of Search: 364/498, 364/496, 364/497, 364/571.01, 364/571.02, 364/571.04, 250/252.1, 250/281, 250/282, 73/23.21, 73/23.22, 73/23.36, 73/23.37, 436/173
• US Class Current: 702/23
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: H01J 49/02 Details

Abstract

A method of creating a library of standardized spectral data and identifying a sample by searching the standardized library for a match with the sample spectrum. The method entails determining and applying a transfer function which equalizes instrument bias between instruments and within the same instruments over time. A transfer function is specific to a particular instrument, and is based on the relationship between a reference spectrum of a standard as stored in a library and a spectrum of the standard obtained on the particular instrument of interest. This method provides enhanced library searching capabilities.

Claims

1. A method of creating a library of standardized spectral data comprising the steps of:

(a) acquiring at least one reference spectrum over a spectral region of interest wherein each reference spectrum is representative of the spectrum of a standard, each reference spectrum being referred to as unbiased reference spectrum, said unbiased reference spectrum being stored and retrievable;

(b) acquiring at least one working spectrum over a corresponding spectral region on a working instrument, each working spectrum being representative of the spectrum of an equivalent standard and each being referred to as a biased working spectrum;

(c) deriving a transfer function from the unbiased reference spectra and the biased working spectra, the transfer function mathematically equates the biased working spectra to the unbiased reference spectra;

(d) during the same time interval as step (b), acquiring a spectrum of an additional standard on the working instrument over the corresponding spectral region, the spectrum of the additional standard being referred to as a biased spectrum of the additional standard;

(e) applying the transfer function of step (c) to the biased spectrum of the additional standard to obtain an unbiased reference spectrum of the additional standard; and

(f) storing at least a portion of the unbiased reference spectrum of the additional standard in the library.

2. The method of claim 1 wherein the working spectra and the reference spectra are collected on separate instruments.

3. The method of claim 1 wherein the spectral data in the library comprises spectra having discrete peaks.

4. The method of claim 1 wherein the spectral data in the library comprises spectra having broadened peaks.

5. The method of claim 1 wherein the additional standard comprises a known compound of a known concentration such that the amount of the known concentration is retrievable.

6. The method of claim 1 wherein steps (b) through (f) are repeated.

7. The method of claim 1 wherein steps (d) through (f) are repeated.

8. A method of identifying a sample, said method comprising the steps of:

(a) acquiring a standardized library of reference spectra from a group of standards wherein the library of reference spectra is representative of the spectra of said group of standards, each spectrum in the library of reference spectra being referred to as an unbiased reference spectrum, said unbiased reference spectra being stored and retrievable;

(b) acquiring a sample spectrum; and

(c) searching the library of reference spectra for a match with the sample spectrum, wherein the standardized library of reference spectra is acquired by the method of claim 1.

9. A method of identifying a sample, said method comprising the steps of:

(a) acquiring a standardized library of reference spectra from a group of standards wherein the library of reference spectra is representative of the spectra of said group of standards, each spectrum in the library of reference spectra being referred to as an unbiased reference spectrum, said unbiased reference spectra being stored and retrievable;

(b) acquiring an unbiased sample spectrum; and

(c) searching the library of reference spectra for a match with the sample spectrum,

wherein the unbiased sample spectrum is acquired by the steps of;

(i) acquiring at least one working spectrum over a spectral region of interest on a working instrument, each said working spectrum being representative of a spectrum of an equivalent standard and being referred to as a biased working spectrum, each said equivalent standard being selected from said group of standards;

(ii) deriving a transfer function from the biased working spectra and the unbiased reference spectra, the transfer function mathematically equates the working spectra to the corresponding unbiased reference spectra;

(iii) during the same time interval as step (i), acquiring a biased sample spectrum of the sample on the working instrument; and

(iv) applying the transfer function of step (ii) to the biased sample spectrum to obtain an unbiased sample spectrum.

10. A method of identifying a sample, said method comprising the steps of:

(a) acquiring a standardized library of reference spectra from a group of standards wherein the library of reference spectra is representative of the spectra of said group of standards, each spectrum in the library of reference spectra being referred to as an unbiased reference spectrum, said unbiased reference spectra being stored and retrievable;

(b) acquiring at least one working spectrum over a corresponding spectral region on a working instrument, each said working spectrum being representative of the spectrum of an equivalent standard and being referred to as a biased working spectrum, each said equivalent standard being selected from said group of standards;

(c) deriving a transfer function from the biased working spectra and the unbiased reference spectra, the transfer function mathematically equates the working spectra to the unbiased reference spectra;

(d) during the same time interval as step (b), acquiring a biased sample spectrum of the sample on the working instrument over the corresponding spectral region;

(e) applying the transfer function of step (c) to the biased sample spectrum to obtain an unbiased sample spectrum; and

(f) searching the standardized library of reference spectra for a match with the unbiased sample spectrum to aid in the identification at least one component in the sample giving rise to said sample spectrum.

11. The method of claim 10 wherein at least one standard in the group of standards comprises a known compound of known concentration, and the concentration of at least one component in the sample is determined.