MEDIAN FILTER FOR LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY DATA

• US 20050109928A1
• Filed: 09/07/2004
• Published: 05/26/2005
• Est. Priority Date: 11/27/2000
• Status: Active Grant

• Current Assignee: Caprion Proteomics Inc. (CellCarta Biosciences, Inc.)
• Original Assignee: Surromed Incorporated
• Inventors: Hastings, Curtis A.
• Granted Patent: US 6,936,814 B2
• Time in Patent Office: Days
• US Class Current: 250/281
• 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 30/8641 Baseline
• CPC Class Codes: H01J 49/0036 Step by step routines describing the handling of the data generated during a measurement
• CPC Class Codes: H01J 49/0431 for liquid samples interfaces to liquid chromatographs G01N30/7233

Abstract

High-intensity, spiked noise is reduced in chromatography-mass spectrometry data by applying a nonlinear filter such as a moving median filter to the data. The filter is applied to individual mass chromatograms, plots of ion abundance versus retention time for each detected mass-to-charge ratio, and the filtered chromatograms are combined to form a filtered total ion current chromatogram. Standard linear filters are not effective for reducing noise in liquid chromatography-mass spectrometry (LC-MS) data because they assume a normal distribution of noise. LC-MS noise, however, is not normally distributed.

Claims

1. Apparatus for characterizing a chemical sample, comprising:

a chromatography instrument operatively associated with a mass spectrometer; and

a processor comprising means for obtaining a chromatogram comprising signal data and noise date from a series of mass spectra of said sample produced by said chromatography instrument and said mass spectrometer, said processor further comprising means for applying a median filter to said chromatogram to remove at least some of said noise data, thereby producing a filtered chromatogram.

2. The apparatus of claim 1, wherein said chromatogram is a total ion chromatogram and said filtered chromatogram is a filtered total ion chromatogram.

3. The apparatus of claim 2, wherein said processor further comprises means for generating individual chromatograms from said total ion chromatogram, wherein said median filter is applied to said individual chromatograms.

4. The apparatus of claim 1, wherein said median filter is a moving median filter.

5. The apparatus of claim 1, wherein said median filter is a modified median filter.

6. The apparatus of claim 1, wherein said processor further comprises means for selecting a parameter of said median filter in dependence on a scan rate of said mass spectrometer.

7. The apparatus of claim 1, wherein said processor further comprises means for selecting a parameter of said median filter in dependence on subsequent data analysis of said mass spectra.

8. The apparatus of claim 7, wherein said subsequent data analysis comprises peak selection.

9. The apparatus of claim 2, wherein said processor further comprises means for performing a component detection analysis on said filtered total ion chromatogram.

10. The apparatus of claim 1, wherein said chromatography instrument is a liquid chromatography instrument.