Quantitative analysis method using mass spectrometer

Patent metadata

Field	Value
Publication number	US-8969791-B2
Application number	US-201114354385-A
Country	US
Kind code	B2
Filing date	Oct 28, 2011
Priority date	Oct 28, 2011
Publication date	Mar 3, 2015
Grant date	Mar 3, 2015

Abstract

In an MS unit, both an intensity of an ion having the highest intensity among the ions originating from a compound as the target of quantitative determination and an intensity of an isotopic ion are measured. A saturation detector determines whether or not digital data produced by an A/D converter from ion-intensity signals have reached a saturation level. A data selection controller selects the ion-intensity data showing the highest intensity when the signal is not saturated or the intensity data of the isotopic ion when the saturation has occurred or is probable to occur. When the latter data is selected, an ion intensity converter converts the intensity data into values corresponding to the intensity data of the highest-intensity ion by multiplying the intensity data by a factor calculated from a known isotopic abundance ratio.

First claim

The invention claimed is:

1. A quantitative analysis method for determining a quantity of a target compound based on an ion intensity obtained by detecting an ion originating from the target compound using a mass spectrometer, the method using an intensity of a product ion obtained by selecting and fragmenting an ion originating from a target compound, and the method including following steps:
in a measurement of a sample containing a target compound, an ion intensity at a mass-to-charge ratio of an ion having a highest intensity among product ions obtained by performing an MS n analysis using different kinds of ions originating from the target compound as precursor ions is detected, and additionally, an ion intensity at a mass-to-charge ratio of another ion having an intensity lower than the highest intensity by a predetermined proportion is detected;
a detection result of the ion intensity at the mass-to-charge ratio of the ion having the intensity lower than the highest intensity is converted into the ion intensity at the mass-to-charge ratio of the ion having the highest intensity; and
in a case where the ion intensity at the mass-to-charge ratio of the ion having the highest intensity is expected or probable to exceed a saturation level, the ion intensity obtained by the aforementioned conversion is used to create a calibration curve for quantitative determination or to derive a quantitative value with reference to the calibration curve.

2. The quantitative analysis method using a mass spectrometer according to claim 1 , wherein:
the ion having the highest intensity is a principal ion composed of principal isotopes, while the ion having an intensity lower than the highest intensity by a predetermined proportion is a subsidiary ion containing an isotope other than the principal isotopes.

3. The quantitative analysis method using a mass spectrometer according to claim 2 , wherein:
the predetermined proportion is an abundance ratio between the principal ion and the subsidiary ion, the abundance ratio being calculated based on a known isotopic abundance ratio, and the aforementioned conversion is performed using the abundance ratio determined by theoretical calculation.

4. The quantitative analysis method using a mass spectrometer according to claim 2 , wherein:
the aforementioned conversion is performed using a ratio between an intensity of a peak corresponding to the principal ion and that of a peak corresponding to the subsidiary ion, the ratio being determined by an actual measurement of a sample.

5. The quantitative analysis method using a mass spectrometer according to claim 1 , wherein:
the intensity of the ion having the highest intensity, and the intensity of the ion having an intensity lower than the highest intensity by a predetermined proportion, are obtained by performing a selective reaction monitoring measurement in which the mass-to-charge ratios of these two ions are set as the ions to be detected.

6. The quantitative analysis method using a mass spectrometer according to claim 1 , wherein:
the intensity of the ion having the highest intensity, and the intensity of the ion having an intensity lower than the highest intensity by a predetermined proportion, are obtained by performing a scan measurement over a range of mass-to-charge ratios including the mass-to-charge ratios of these two ions.

7. The quantitative analysis method using a mass spectrometer claim 1 , wherein:
the mass spectrometer is used for performing a mass spectrometry of compounds separated by a chromatograph, and the calibration curve represents a relationship between a chromatogram peak area originating from a target compound and a compound concentration.

8. A mass spectrometer to be used for the mass analysis method according to claim 1 , comprising:
a) a measurement executor for detecting, in a measurement of a sample containing a target compound, an ion intensity at the mass-to-charge ratio of an ion having a highest intensity among product ions obtained by performing an MS n analysis using different kinds of ions originating from the target compound as precursor ions as well as an ion intensity at a mass-to-charge ratio of another ion having an intensity lower than the highest intensity by a predetermined proportion;
b) a conversion processor for converting a detection result of the ion intensity at the mass-to-charge ratio of the ion having the intensity lower than the highest intensity into the ion intensity at the mass-to-charge ratio of the ion having the highest intensity;
c) a saturation detector for detecting a state in which the ion intensity at the mass-to-charge ratio of the ion having the highest intensity has exceeded, or is probable to exceed, a saturation level; and
d) a quantitative determination processor for performing a process of creating a calibration curve for quantitative determination or deriving a quantitative value with reference to the calibration curve, using the ion intensity at the mass-to-charge ratio of the ion having the highest intensity if the state of saturation or probable saturation has not been detected by the saturation detector, or using the ion intensity obtained through conversion by the conversion processor if the state of saturation or probable saturation has been detected by the saturation detector.

Assignees

• Mukaibatake Kazuo
• Shimadzu Corp

Inventors

• Mukaibatake Kazuo

Classifications

• H01J49/0036 Primary

  Step by step routines describing the handling of the data generated during a measurement · CPC title

• G01N30/72

  Mass spectrometers {(mass spectrometers per se H01J49/00)} · CPC title

• H01J49/26

  Mass spectrometers or separator tubes · CPC title

• H01J49/0031 Primary

  Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence) · CPC title