Chromatographic and mass spectral date analysis

• US 20060255258A1
• Filed: 04/10/2006
• Published: 11/16/2006
• Est. Priority Date: 04/11/2005
• Status: Abandoned Application

• Current Assignee: Cerno Bioscience LLC
• Original Assignee: Cerno Bioscience LLC
• Inventors: Wang, Yongdong, Gu, Ming
• Application Number:
  US11/402,238
• Publication Number:
  US 20060255258A1
• Time in Patent Office: Days
• US Class Current: 250/282
• CPC Class Codes: G01N 2030/042 Standards
• CPC Class Codes: G01N 30/72 Mass spectrometers mass spectrometers per se H01J49/00
• CPC Class Codes: G01N 30/8624 Detection of slopes or peaks; baseline correction
• CPC Class Codes: G01N 30/8637 Peak shape
• CPC Class Codes: G01N 30/8665 for calibrating the measuring apparatus
• CPC Class Codes: G06F 2218/00 Aspects of pattern recognition specially adapted for signal processing

Abstract

Apparatus, methods, and computer readable media having computer code for calibrating chromatograms to achieve chromatographic peak shape correction, noise filtering, peak detection, retention time determination, baseline correction, and peak area integration. A method for processing a chromatogram, comprises obtaining at least one actual chromatographic peak shape function from one of an internal standard, an external standard, or an analyte represented in the chromatogram; performing chromatographic peak detection using known peak shape functions with regression analysis; reporting regression coefficients from the regression analysis as one of peak area and peak location; and constructing a calibration curve to relate peak area to known concentrations in the chromatogram. A method for constructing an extracted ion chromatogram, comprises calibrating a low resolution mass spectrometer for both mass and peak shape in profile mode; performing mass spectral peak analysis and reporting both mass locations and integrated peak areas; specifying a mass defect window of interest; summing up all detected peaks with mass defects falling within the specified mass defect window to derive summed intensities; and plotting the summed intensities against time to generate a mass defect filtered chromatogram.

Claims

1. A method for processing a chromatogram, comprising:

obtaining at least one actual chromatographic peak shape finction from one of an internal standard, an external standard, or an analyte represented in the chromatogram;

performing chromatographic peak detection using known peak shape functions with regression analysis;

reporting regression coefficients from the regression analysis as one of peak area and peak location; and

constructing a calibration curve to relate peak area to known concentrations in a calibration series.

2. The method of claim 1, where the chromatogram is a time-dependent signal representing the arrival and disappearance of an analyte.

3. The method of claim 2, where the time-dependent signal includes one of a chromatogram derived from LC/MS/MS and a plasmagram from an ion mobility spectrometer.

4. The method of claim 1, further comprising:

defining a target chromatogram mathematically; and

converting the actual chromatogram into the target chromatogram.

5. The method of claim 1, where known peak shape function is one of actual chromatographic peak shape function or target peak shape function.

6. The method of claim 1, further comprising calibrating the chromatogram by:

specifying at least one target chromatographic peak shape function;

obtaining a calibration filter; and

applying the calibration filter to transform a measured chromatogram into a calibrated chromatogram.

7. The method of claim 6, further comprising performing multivariate statistical analysis on the calibrated chromatogram to achieve at least one of identification, classification, and quantification.

8. The method of claim 6, further comprising:

using multiple standards across a retention time range of interest; and

obtaining a calibration filter for a plurality of retention times within the time range.

9. The method of claim 6, further comprising transforming an x axis of a measured chromatogram to normalize the peak shape function.

10. The method of claim 6, wherein the calibration filter is obtained by performing a deconvulution operation.

11. The method of claim 10, wherein the deconvolution operation comprises one of a matrix operation or a Fourier transform.

12. The method of claim 1, wherein the peak areas are first ratioed to those of the internal standards, prior to constructing the calibration curve.

13. The method of claim 1, further comprising using the calibration curve to calculate unknown concentration of an analyte.

14. The method of claim 1, further comprising using the peak detection to produce at least one of time measurements and standardized mobility for qualitative analysis.

15. The method of claim 1, where the actual chromatographic peak shape function is one of actually measured or numerically derived from partially overlapping chromatographic peaks.

16. The method of claim 15, where the partially overlapping chromatographic peaks are from chiral compounds.

17. An analytical instrument operating in accordance with the method of claim 1.

18. A computer readable medium having computer code thereon for performing the method of claim 1, said code being for use by a computer operating with an analytical instrument.

19. A method for processing a mass spectrum comprising:

calibrating the mass spectrum for at least one of mass and peak shape;

constructing a peak component matrix;

performing a regression between the mass spectrum and the peak component matrix;

reporting at least one regression coefficient as related to the concentration of an ion; and

using the reported regression coefficients from a plurality of mass spectra for one of quantitative or qualitative analysis

20. The method of claim 19, wherein the peak component matrix contains at least one of linear and nonlinear baseline components.

21. The method of claim 19, wherein the peak-component matrix contains-the isotope profile of at least one ion of interest.

22. The method of claim 21, wherein the ion of interest is one of possible metabolites of a known drug.

23. The method of claim 21, where the isotope profile is one of theoretically calculated based on elemental composition, and actually measured

24. The method of claim 19, wherein the peak component matrix contains the derivative of the isotope profile of at least one ion.

25. The method of claim 24, wherein the derivative is one of theoretically calculated based on formula and equations, and numerically calculated based on being actually measured.

26. The method of claim 19, wherein the peak component matrix contains the isotope profile of both the native and labeled ion linearly combined or each individually.

27. The method of claim 19, further comprising:

constructing a calibration curve; and

relating the at least one reported coefficient to actual concentration for the purpose of quantitative analysis.

28. The method of claim 27, wherein the regression is performed on both an internal standard ion and an analyte ion and reported coefficients are ratioed between the internal standard ion and the analyte ion prior to constructing the calibration curve.

29. The method of claim 19, further comprising:

plotting a reported coefficient related to an ion concentration against retention time to generate an extracted ion chromatogram.

30. The method of claim 19, further comprising:

reporting at least one of fitting residual and mass error from the regression analysis; and

using at least one of said fitting residual and mass error to construct a weight function.

31. The method of claim 30, further comprising applying the weight function to the regression coefficient related to the ion concentration to reduce interferences from coexisting ions.

32. The method of claim 31, further comprising plotting the weighted regression coefficient against the retention time to generate an extracted ion chromatogram.

33. An analytical instrument, including a mass spectrometer, operating in accordance with the method of claim 19.

34. A computer readable medium having computer code thereon for performing the method of claim 19, said code being for use by a computer operating with an analytical instrument including a mass spectrometer.

35. A method for constructing an extracted ion chromatogram, comprising:

calibrating a low resolution mass spectrometer for both mass and peak shape in profile mode;

performing mass spectral peak analysis and reporting both mass locations and integrated peak areas;

specifying a mass defect window of interest;

summing up all detected peaks with mass defects falling within the specified mass defect window to derive summed intensities; and

plotting the summed intensities against time to generate a mass defect filtered chromatogram.

36. The method of claim 35, wherein the mass spectral peak analysis is performed by a fast algorithm including a-simple function.

37. The method of claim 36, wherein the simple function is a quadratic function.

38. The method of claim 35, wherein the mass defect window is within a small mass defect range that includes the mass defect of a drug of interest.

39. The method of claim 35, further comprising subjecting the detected peaks to a threshold based on at least one of mass error, peak area error, and peak area magnitude, before said intensities are summed.

40. An analytical instrument, including a mass spectrometer, operating in accordance with the method of claim 35.

41. A computer readable medium having computer code thereon for performing the method of claim 35, said code being for use by a computer operating with an analytical instrument including a mass spectrometer.