CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2018/020699, filed May 30, 2018.

TECHNICAL FIELD

The present invention relates to a spectrum data processing device for determining the quantity of a specific component in a specimen using a spectrum having a peak top at a position depending on the component contained in the specimen, such as a mass spectrum obtained by a mass spectrometer or a spectral spectrum obtained by a spectrophotometer such as an infrared spectrophotometer or a Raman spectrophotometer, and relates to an analyzer including an analysis unit for acquiring the spectrum and the spectrum data processing device.

BACKGROUND ART

Conventionally, it has been practiced to determine the quantity of a component contained in a specimen based on a mass spectrum acquired by a mass spectrometer. For example, when a distribution of a component on a surface of a specimen such as a piece of living body tissue is to be observed, the quantity (concentration) of the component for each measurement point is obtained from a mass spectrum obtained by performing mass spectrometry on each of a plurality of measurement points (minute regions) on the surface. Mass spectrometry method for each measurement point includes, for example, a method of irradiating a measurement point with a laser and analyzing ions generated by the irradiation (see, for example, Patent Literature 1), and a method of analyzing ions generated by bringing a probe into contact with a measurement point and applying a high voltage to the probe (Patent Literature 2).

In a mass spectrum obtained by a mass spectrometer, ideally, the intensity value of ions derived from the components is obtained for each value of mass-to-charge ratios (which is formally represented by italicized “m/z”; however, will be described as non-italicized “m/z” hereinafter due to the restrictions of electronic filing). Actually, however, a peak profile having a width centered on the m/z value is obtained. For example, in a time-of-flight mass spectrometer, a mass spectrum is obtained with the time from the introduction of ions into the mass spectrometer to the detection by the detector on the horizontal axis and the detection intensity on the vertical axis. Even if a group of ions have the same value of m/z, the respective detection time of the ions varies due to the deviation in the flight direction or other factors, resulting in a peak profile having a width. In the case of such a mass spectrum, the area of a peak, rather than the height of the peak top, better reflects the quantity of the component from which the ion having m/z corresponding to the peak is derived. Therefore, by measuring the area for each peak, it is possible to determine the quantity of the component corresponding to the m/z value at the center of the peak with high accuracy.

When the quantity of a target component in a specimen is determined using a mass spectrum, usually, mass spectra of a plurality of standard specimens having known and varied concentrations of the target component are acquired before or after acquiring a mass spectrum of the objective specimen. Then, the area of the peak corresponding to the target component is obtained from each of the plurality of mass spectra, and a calibration curve showing the relationship between the concentrations and the areas is created. From the mass spectrum obtained for the specimen to analyze, the area of the peak corresponding to the target component is measured and applied to the calibration curve, whereby the concentration of the target component in the specimen is obtained.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2014-520259 A

Patent Literature 2: JP 2014-044110 A

SUMMARY OF INVENTION

Technical Problem

Since a peak profile of the mass spectrum has a width as described above, the both end positions of the peak along the horizontal axis (m/z) (hereinafter referred to as both end positions) must be determined when measuring the area of the peak. Also, the baseline of the mass spectrum must be determined to eliminate the effects of background noise. These both end positions and the baseline may be automatically determined by a computer. However, they cannot always be determined appropriately when, for example, a peak due to an impurity overlap, and both end positions and a baseline may have to be determined manually in some time. If manual determination is adopted when creating a calibration curve, try-and-error operations for moving the both end positions and/or the baseline and establishing a calibration curve need to be repeated until suitable both end positions and baseline are found, which is time-consuming.

So far, the case of a mass spectrum has been described as an example, but the same problem occurs when a calibration curve is created from a spectrum other than the mass spectrum such as a spectral spectrum.

The problem to be solved by the present invention is to provide a spectrum data processing device, a data processing device for a mass spectrometer, and a mass spectrometer including the data processing device for a mass spectrometer capable of easily setting the correct both end positions and baseline of a peak of the spectrum when creating a calibration curve used for determining the quantity of the component in a specimen using the spectrum having a peak top at a position depending on the component contained in the specimen, such as a mass spectrum obtained by a mass spectrometer or a spectral spectrum obtained by a spectrophotometer.

Solution to Problem

The spectrum data processing device according to the present invention, which has been made to solve the above problems, is a device configured to create, based on a plurality of spectra each obtained from each of a plurality of specimens containing a predetermined component at known concentrations different from one another, a calibration curve showing a relationship between a concentration of the component in the specimen and an area of a peak corresponding to the component of a spectrum of the specimen, where each of the plurality of spectra has a peak top at a position depending on a component contained in a specimen, the device including:

a) a display unit having a spectrum display region and a calibration curve display region;

b) a spectrum display controller configured to display one or more of the spectra in the spectrum display region;

c) a peak range setting unit configured to allow an operator to set both end positions of a peak or a position of a baseline corresponding to the component included in the displayed spectrum;

d) a peak range determination unit configured to determine the both end positions of the peak or the position of the baseline according to a predetermined standard;

e) an area calculation unit configured to calculate an area of the peak based on the both end positions of the peak and the position of the baseline set by the peak range setting unit or determined by the peak range determination unit; and

f) a calibration curve creation unit configured to create a calibration curve based on the area of the peak calculated by the area calculation unit and a known concentration of the peak and display it in the calibration curve display region.

In the spectrum data processing device according to the present invention, the spectrum display controller displays, in the spectrum display region, one or more of spectra, such as mass spectra or spectral spectra, having a peak top at a position depending on a predetermined component contained in the specimen obtained from a plurality of specimens (standard specimens) containing a predetermined component at known concentrations different from one another. For the peak corresponding to the component included in the spectrum displayed in the spectrum display region, the peak range setting unit allows an operator to set both end positions of the peak or the position of the baseline. Here, the operator may set only one of the both end positions of the peak and the position of the baseline, or may set both. When the operator sets only one of them, the peak range determination unit determines the one not set by the operator according to a predetermined standard. Alternatively, the peak range determination unit first determines the both end positions of the peak and the position of the baseline according to a predetermined standard, and the peak range setting unit, when the operator changes one or both of them to an arbitrary position, may set it to the change position.

For example, the peak range setting unit superimposes and displays marks (lines, symbols, etc.) indicating the both end positions of the peak or/and the position of the baseline on the spectrum displayed in the spectrum display region by the spectrum display controller. Then, by having the operator perform an operation of moving the mark with an input device such as a mouse or a touch panel, the both end positions of the peak and the position of the baseline can be set. Alternatively, it is possible to have the operator input numerical values indicating the both end positions of the peak and the position of the baseline.

The area calculation unit calculates the area of the peak corresponding to the component based on the both end positions of the peak and the position of the baseline thus input by the operator or determined by the peak range determination unit. Then, the calibration curve creation unit creates a calibration curve based on the calculated area of the peak and the known concentration of the peak, and displays it in the calibration curve display region.

By the above operation, the spectrum and the calibration curve are displayed on the same display unit (the spectrum display region and the calibration curve display region of the display unit), so that the operator can change the both end positions of the peak and the position of the baseline while seeing the calibration curve. In addition, each time the operator inputs the both end positions of the peak corresponding to the component or the position of the baseline, a calibration curve is created based on those positions and displayed in the calibration curve display region, so that there is no need to perform operations to recreate the calibration curve each time they are changed to find appropriate both end positions of the peak or position of the baseline. Therefore, the correct both end positions and baseline position can be easily set.

In the spectrum data processing device according to the present invention, it is desirable that,

the area calculation unit calculates the area of the peak each time the both end positions of the peak or the position of the baseline are set by the peak range setting unit or determined by the peak range determination unit, and

the calibration curve creation unit creates the calibration curve each time the area calculation unit calculates the area of the peak, and displays it in the calibration curve display region.

As a result, the created (changed) calibration curve is automatically displayed each time the operator sets the both end positions of the peak or the position of the baseline, which makes the operation easier. In particular, when the operator sets the positions of them by moving the mark indicating the both end positions of the peak or the position of the baseline, the display of the calibration curve is updated moment by moment as the mark is moved, so the operator can search for the optimum both end positions of the peak and baseline position while moving the mark, which makes it easier to set the positions.

In the spectrum data processing device according to the present invention, it is desirable that,

the display unit has a matching degree display region for displaying a matching degree between an area calculated by the area calculation unit and the concentration corresponding to the area, and the calibration curve, and

the device further includes

a matching degree calculation unit configured to calculate the matching degree and display it in the matching degree display region each time the calibration curve is created by the calibration curve creation unit.

As a result, the matching degree is displayed in the matching degree display region each time the calibration curve is created by the calibration curve creation unit, that is, each time the both end positions of the peak or the position of the baseline is input. The operator can determine whether the both end positions of the peak or the position of the baseline of the input target component is appropriate based on the displayed matching degree. As the matching degree, a correlation coefficient, a square value of the correlation coefficient, or the like can be used.

It is desirable that the spectrum display controller further displays a mark (feature display) on the peak corresponding to the component in the spectrum to be displayed in the spectrum display region. This makes it clear which peak the operator should set the both end positions of the peak and the position of the baseline, which makes the operation easier. For example, the spectrum display controller identifies a peak whose peak top is located within a predetermined range from a value (m/z of a mass spectrum, or a wavelength, a wave number, a frequency, etc. of a spectral spectrum) input by the operator in advance as a peak corresponding to the component in the spectrum and can mark the peak. Alternatively, the values of various components are stored as a database in advance, and the peak corresponding to the component may be identified by using the value acquired from the database based on the name or the like of the component input by the operator.

In the spectrum data processing device according to the present invention, it is desirable that,

the display unit has a distribution image display region for displaying the distribution of the concentration of the component obtained from the spectrum obtained at each of a plurality of positions in the specimen to be analyzed, and

the device can be configured to further include,

an intra-specimen position information acquiring unit configured to acquire, for the spectrum obtained at each of the plurality of positions, an intra-specimen position at which the spectrum is obtained;

a component quantifying unit configured to obtain a concentration of the component by applying the area of the peak calculated by the area calculation unit to a calibration curve for the spectrum obtained at each of the plurality positions each time the calibration curve is created by the calibration curve creation unit; and

a distribution image display controller configured to display information on the concentration at a position in the distribution image display region corresponding to the position for the spectrum obtained at each of the plurality of positions each time the concentration is obtained by the component quantifying unit.

Information on the concentration can be represented by, for example, different colors or difference in brightness depending on the concentration. Alternatively, the information on the concentration can be also represented by a three-dimensional view in which the position is represented two-dimensionally on the base plane and the concentration is represented by the height.

With such a configuration, each time a calibration curve is created by the calibration curve creation unit (that is, each time the both end positions of the peak or the position of the baseline is set by the peak range setting unit or determined by the peak range determination unit), a distribution image showing the distribution of the concentration of the component to be analyzed in the specimen to be analyzed is displayed. As a result, when the operator changes the both end positions of the peak or the position of the baseline, not only the calibration curve is automatically changed, but also the distribution image is also automatically changed, and the analysis result based on the changed calibration curve can be obtained immediately.

The spectrum data processing device according to the present invention can be suitably used when performing mass spectrometry, spectroscopic analysis, or the like on each of the plurality of measurement points (minute regions) described above, but if the operation of creating a calibration curve is performed using the spectrum of a standard specimen having a known concentration, the present invention can be applied without limitation to the above example.

The analyzer according to the present invention includes:

a) an analysis unit configured to acquire a spectrum having a peak top at a position depending on a component contained in a specimen; and

b) a spectrum data processing device that creates, based on a spectrum obtained by the analysis unit from each of a plurality of specimens containing a predetermined component at known concentrations different from one another, a calibration curve showing a relationship between a concentration of the component in each specimen and an area of a peak corresponding to the component of the spectrum of the specimen, the device including,

b-1) a display unit having a spectrum display region and a calibration curve display region,

b-2) a spectrum display controller configured to display one or more of the spectra in the spectrum display region,

b-3) a peak range setting unit configured to allow an operator to set both end positions of a peak or a position of a baseline corresponding to the component included in the displayed spectrum,

b-4) a peak range determination unit configured to determine the both end positions of the peak or the position of the baseline according to a predetermined standard,

b-5) an area calculation unit configured to calculate an area of the peak based on the both end positions of the peak and the position of the baseline set by the peak range setting unit or determined by the peak range determination unit, and

b-6) a calibration curve creation unit configured to create a calibration curve based on the area of the peak calculated by the area calculation unit and the known concentration of the peak and display it in the calibration curve display region.

Advantageous Effects of Invention

According to the present invention, when creating a calibration curve to be used when determining the quantity of a component in a specimen using a spectrum, it is possible to easily set correct both end positions of a peak and baseline of the spectrum.

