JPH11344482A - Mass spectrometer system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent misalignment by calculating a holding time to perform isomer assignment by using the calculated holding time. SOLUTION: This system is equipped with a chromatograph 1 which separates compds. temporally; a mass spectrometer 2 which selects specific ions to measure an SIM chromatogram separated temporally by chromatograph; and a data processing means 3 which determines a correction curve correcting a holding time by using an internal standard compd. based on the measured SIM chromatogram, and determines the calculated holding times of respective isomers of a compd. to be quantitatively analyzed from the correction curve to assign isomer peaks to perform quantitative calculation, and a compd. having a plurality of isomers of the same mass number is quantitatively analyzed. Further, an output means 5 is provided to output the measured SIM chromatograms and the chromatogram patterns of the calculated holding times of respective isomers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mass spectrometry system for quantitatively analyzing compounds having a plurality of isomers having the same mass number.

[0002]

2. Description of the Related Art Chromatography and mass spectrometry (MS) are used for quantitative analysis of trace amounts of substances having a large amount of impurities (miscellaneous substances).
Is used. According to this system, a compound to be quantified is temporally separated by chromatography, and only a specific ion of the compound to be quantified can be selectively observed by a mass spectrometer. Dioxins (PCDDs / PCDFs) have a large number of isomers (Isomers), and each isomer is separated temporally by chromatography and is obtained as a SIM (Selected Ion Monitoring) chromatogram of a specific ion measured by a mass spectrometer. Observed. In the case of a compound having such isomers (Compound), each isomer is almost temporally separated by chromatography, and a peak of each isomer is observed on one SIM chromatogram. However, some isomers are not separated by chromatography and cannot be separated by mass spectrometry because they have the same mass.

The compound is quantified from the peak intensity of the SIM chromatogram. At this time, an internal standard compound is added to the sample to remove the influence of the fluctuation of the apparatus.
In the concentration calculation for measuring the IM chromatogram, the ratio between the peak of the internal standard compound and the peak of the quantitative compound is used. This is called the internal standard method.

Hereinafter, dioxin will be described as an example.
For dioxin analysis, gas chromatography (GC) is used as chromatography. Then, remove the influence of miscellaneous materials and use only dioxin compounds as SIM
To obtain a chromatogram, for example, a resolution of 10,000
The high-resolution mass spectrometer described above is used. In the measurement by the mass spectrometer, a highly sensitive SIM method is used, an internal standard method is used as a quantification method, and for example, a 13C compound is used as the internal standard substance.

FIG. 6 is a diagram for explaining the flow of quantitative analysis of a dioxin compound, and FIG. 7 is a diagram showing an example of a SIM chromatogram of one compound T4CDF of dioxins. In order to shorten the time of the quantitative analysis operation, measurement and quantitative analysis of a plurality of compounds of dioxins are performed by one injection. The procedure of the quantitative analysis is as follows. First, a SIM chromatogram of a dioxin compound is measured by GC / MS (step S2).
1). Next, the peak of the SIM chromatogram is detected (step S22), and the detected peak and the dioxin isomer are associated (assigned), and only the dioxin isomer peak is extracted (step S23).
Then, a quantitative calculation is performed using the extracted isomer peak to calculate the concentration (step S24).

Compound T4C, one of dioxins
DF has 38 isomers. Most of these isomers are temporally separated by gas chromatography (GC) and have the same mass. Therefore, as shown in FIG.
Appears as a separate peak on the chromatogram. Using this peak intensity, quantitative analysis is performed as described above.

[0007]

However, since dioxin is a trace analysis, and the detected peak includes a peak due to a foreign substance, the peak detection is not a peak due to a foreign substance, but a peak of a dioxin isomer. Only need to take out. In particular, in the case of a sample having a low concentration, there is a case where a peak due to a foreign substance is mixed and is erroneously recognized as a dioxin peak. In order to prevent this misidentification, the following method is adopted.

[0008] One is a method based on ratio shek.
This involves first measuring the SIM chromatogram of two or more ions using the isotope of the quantitative compound, and calculating the peak ratio of the two SIM chromatograms. Since the abundance ratio of the isotope is known, it is determined whether or not the peak is the dioxin peak according to whether or not the peak ratio is the same as the abundance ratio. Determination of the peak by this ratio shek
It is widely used in analysis using a mass spectrometer.

The other is a method of performing peak judgment by an analyst. The time when the peak appears (retention time)
Determined by GC column and already reported in the literature as relative retention times (eg JJRyan, HBSCo
nacher, lgpanopio, BP-Y.Lau, jahardy, Y.Masud
a, J. Chromatogr. 541 (1991) 131-183). In addition, there is a specific peak pattern depending on the type of sample (in the case of dioxin, exhaust gas, drainage, ash). Therefore, based on the peak retention time and the peak pattern, the analyst determines whether or not the peak is a dioxin peak.

As described above, the isomer assignment of dioxins is carried out based on the retention time of the SIM chromatogram and the intensity pattern. Usually, this operation is performed manually by referring to the literature and data already measured by the analyst. It is done in.

The holding time may be shifted due to the following factors. Since the dioxin quantitative analysis is a trace analysis, various substances are mixed in the sample. Therefore, depending on how dirty the sample is,
Over time, the chromatogram retention time may shift. Furthermore, after measuring multiple samples,
To remove dirt, remove one sample from the sample introduction end of the column.
m may be cut off. This will slightly shorten the chromatogram retention time. Of course, when the columns are exchanged, even if the columns are of the same type, they do not always show exactly the same retention time.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to calculate a retention time and perform isomer assignment using the calculated retention time to prevent mis-assignment. Things.

Accordingly, the present invention provides a mass spectrometry system for quantitatively analyzing a compound having a plurality of isomers having the same mass number. A mass spectrometer for measuring a temporally separated SIM chromatogram and a correction curve for correcting a retention time using a beauty standard compound not based on the measured SIM chromatogram were obtained. From the correction curve, each isomer of a quantitative compound was determined. And a data processing means for obtaining a calculated retention time, assigning an isomer peak, and performing a quantitative calculation.

[0014] The data processing means may determine a reference retention time based on a SIM chromatogram of a compound added as an internal standard compound.
Output means for outputting data, wherein the data processing means converts the measured SIM chromatogram and the chromatogram pattern of the calculated retention time of each isomer into the measured SI
It is characterized in that assignment information is added to each peak of the M chromatogram and output from the output means.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a mass spectrometry system according to the present invention, and FIG.
It is a figure showing the example of IM chromatogram. In the figure, 1 is chromatography, 2 is a mass spectrometer, 3 is an analysis processing control device, 4 is a data storage device, 5 is an output device, 11 is an analysis control unit, 12 is a retention time table, 13 is a correction curve calculation unit, 14 is a retention time calculation unit, 15 is an assignment processing unit, 1
Reference numeral 6 denotes a quantitative calculation processing unit.

In FIG. 1, chromatography 1 is, for example, gas chromatography (GC) in which an isomer of a quantitative compound is temporally separated using an analytical column having a length of several tens of meters (eg, 60 m). The analyzer 2 measures a mass chromatogram, that is, a SIM chromatogram, which captures a temporal change of an ion having a specific mass from a quantitative compound temporally separated by the chromatography 1. The analysis processing control device 3 is a computer that controls the chromatography 1 and the mass spectrometer 2, processes SIM chromatograms of various quantitative compounds measured by the mass spectrometer 2, and performs peak assignment, quantitative calculation, and the like. For example, it includes an analysis control unit 11, a retention time table 12, a correction curve calculation unit 13, a retention time calculation unit 14, an assignment processing unit 15, a quantitative calculation processing unit 16, and the like. The data storage device 4 stores the SI measured by the mass spectrometer 2.
An external storage device for storing M chromatograms and various data processed by the analysis processing control device 3;
Is a display or a printer that outputs the data.

The analysis control section 11 controls the chromatography 1 and the mass spectrometer 2 and takes in SIM chromatograms of various compounds measured by the mass spectrometer 2. The retention time table 12 is a table having a standard retention time of a SIM chromatogram of an internal standard compound (Internal Standard) and a retention time of a SIM chromatogram of various compounds (quantitative compounds) to be analyzed. The correction curve calculation unit 13 refers to the reference retention time of the retention time table 12 from the measured retention time of the SIM chromatogram of the internal standard compound measured by the mass spectrometer 2, thereby obtaining various quantitative compounds QNT-A, QNT- B
Curve T = (1 + a) T ₀ for obtaining the holding time of
Is intended to calculate the + b, for example, the vertical axis T ₀ as a reference holding time of the holding time table 12 for the internal standard Compound IS-A, IS-B as shown in FIG. 2, corresponding to the horizontal axis T to measure Hold time. Retention time calculator 14
Is to correct the retention time of each isomer peak appearing in the SIM chromatogram of the quantitative compound based on the correction curve of the correction curve calculation unit 13, and calculate the calculated retention time of each isomer of the quantitative compound. The assignment processing unit 15 detects a peak of the measured SIM chromatogram of the quantitative compound, sets a retention time window based on the calculated retention time and its allowable range, and calculates the peaks existing in the retention time window as shown in FIG. The peak closest to the retention time is assigned to the isomer. The quantitative calculation processing unit 16 performs quantitative calculation by extracting, for example, only the peak of the dioxin isomer based on the assigned result, and calculating the concentration using the extracted peak of the isomer.

Next, the overall processing flow will be described. FIG.
FIG. 4 is a diagram for explaining the flow of quantitative analysis processing by the mass spectrometry system according to the present invention. FIG. 4 is a diagram showing a display example of a measured SIM chromatogram and a bar showing a pattern of the SIM chromatogram. FIG. 7 is a diagram illustrating a print output example of a display screen.

In the quantitative analysis process, as shown in FIG. 3, first, the internal standard compounds IS-A and IS-B and the quantitative compound Q
The SIM chromatogram of NT-A and QNT-B was measured (step S11), and the internal standard compounds IS-A and IS-
The measurement holding time of the SIM chromatogram of B is obtained (step S12), and a correction curve T = (1 + a) T ₀ + b is calculated (step S13). Next, the calculated retention time of the quantitative compounds QNT-A and QNT-B is determined from the correction curve (step S14), and the isomer peak of the measured quantitative compound of the unknown sample is assigned from the calculated retention time (step S15). . Since the assigned peak corresponds to the dioxin isomer, as shown in FIG. 4, the assigned peak and the other peaks are identified and displayed according to differences in color and other display modes (step S16), and the intensity of the assigned peak is determined. The quantitative calculation is performed by calculating the concentration using (area value) (step S17).

The reference retention time must be determined in advance from a SIM chromatogram of a sample with high impurity concentration and low concentration (internal standard compound). The correction curve is for calculating the calculated retention time, and it has been found that when the deviation of the retention time is small, it can be approximated well by linear correction as shown in FIG.

The calculation of the correction curve is based on the SI of the internal standard compound.
It is determined from the peaks of the M chromatogram. In the case of the linear equation, at least two peaks are required. In order to improve the efficiency of the analysis operation, dioxin uses Q as shown in FIG.
Since a plurality of compounds such as NT-A and QNT-B are measured by one injection, two or more internal standard compounds I
There are isomer peaks of SA and IS-B. Since the internal standard compound is always present since it is added, it has a certain intensity, and the number of peaks of the internal standard compound is small, so that isomer assignment can be easily performed. For example, there is a method of assigning in order of retention time from a strong peak. Correction curve T = (1 + a) T ₀
The coefficients a and b of + b are calculated from the measured retention time of the internal standard compound and the reference retention time by the least square method.

Once the correction curve has been determined, the retention time of the quantitative compound can be calculated, and the range of the retention time can be calculated from the calculated value and the allowable time. Compound peak assignments can be made. At this time, when there are a plurality of peaks in the range, the following method is available. One is to select the peak with the highest intensity, and the other is to select the peak closest to the calculated value. In the case of dioxin, the method of selecting the peak closest to the calculated value was good. The verification can determine whether the assignment is correct using the difference between the calculated retention time and the measured value. If the difference value is large, there is a possibility of misassignment.

In order to clarify the correspondence between the peak of the measured SIM chromatogram and the isomer, a typical SIM chromatogram pattern may be displayed on the screen together with the measured SIM chromatogram as shown in FIG. Very effective. In the display example shown in FIG.
The IM chromatogram, the middle display is the bar chromatogram showing the SIM chromatogram pattern and the calculation retention time, and the lower display is the SIM chromatogram of the internal standard compound. An example of the printout of the screen is shown. FIG. Here, by comparing the upper SIM chromatogram with the middle bar display, for example, FIG.
It can be clearly seen that the X-marked peak does not correspond to the peak of the isomer of T4CDF. Some of these peaks have a ratio check of OK, indicating that determination by ratio check alone is not sufficient.

A bar for displaying a chromatogram pattern can be set based on literature values or measured values as the intensity on the vertical axis and the retention time on the horizontal axis. In addition, since the horizontal axis can be moved, reduced, and enlarged by a primary expression by manual operation, the peak of the measured SIM chromatogram and the pattern of the chromatogram can be matched as needed. This is useful when the automatic isomer assignment is not correctly performed or when the reference retention time is determined.

As described above, the bar display of the chromatogram pattern is used as the user interface. For example, by selecting one of the bars on the screen shown in FIG.
The isomer can be assigned to the peak of the measured SIM chromatogram by ag & Drag. By such a device, the isomer assignment of the peak of the measured SIM chromatogram can be easily performed.

The peaks of the measured SIM chromatogram shown in FIG. 4 are displayed in different colors, for example, as follows. Blue: RetioCheck = NotOK Isomer = NotAssigned Light blue: RetioCheck = OK Isomer = NotAssigned Yellow: RetioCheck = NotOK Isomer = Assigned Green: RetioCheck = OK Isomer = Assigned As a result, the peak ratio check and isomer assignment information become clear at a glance. .

In the display shown in FIG. 4, a SIM chromatogram of the 13C compound is also shown as an internal standard compound, but the 13C compound contains only an important isomer. It is the 2378 isomer. 13C and 1
It can be considered that the retention time is almost the same for 2C. Therefore, the peak of the quantitative compound corresponding to the 2378 peak retention time of 13C is the 2378 isomer, and the assignment can be verified.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the embodiment, dioxin has been described,
In addition to dioxin, compounds having a plurality of similar isomers, such as PCB analysis, can be used for analysis using ordinary internal standard methods. Although the correction curve uses a linear expression, a polynomial, a spline function, or the like may be used. Further, when there is no peak of the internal standard compound, that is, when the internal standard method is not used, a special compound may be added to correct the retention time. Although the chromatogram pattern is displayed in a bar format, it may be displayed as continuous data.

[0029]

As is apparent from the above description, according to the present invention, a correction curve is obtained from the retention time of the peak of the internal standard compound measured by the same injection, and the peak of the quantitative compound is determined using this correction curve. Since the retention time is corrected, it is possible to prevent misassignment of the peak of the quantitative compound due to the contamination of the sample, the change with time, and the deviation of the retention time due to partial cutting of the column. Moreover, since the internal standard compound has a small number of peaks and always has a certain intensity, the assignment can be performed easily and reliably, and the assignment is automated using the calculated retention time obtained from the correction curve. be able to. Further, by displaying the chromatogram based on the calculated retention time and the measurement retention time together, the analysis result can be verified. In addition, by displaying a typical chromatogram pattern, it is easy for the analyst to understand the correspondence between peak retention time and peak pattern, and it is possible to correctly assign isomers of quantitative compounds, Erroneous recognition of peaks due to the above.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a mass spectrometry system according to the present invention.

FIG. 2 is a diagram showing an example of a correction curve and a SIM chromatogram.

FIG. 3 is a diagram illustrating a flow of a quantitative analysis process by the mass spectrometry system according to the present invention.

FIG. 4 is a diagram showing a display example of bars showing measurement SIM chromatograms and SIM chromatogram patterns.

FIG. 5 is a diagram showing a print output example of the display screen of FIG. 4;

FIG. 6 is a diagram for explaining the flow of quantitative analysis of a dioxin compound.

FIG. 7 is a diagram showing an example of a SIM chromatogram of one compound T4CDF of dioxins.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chromatography, 2 ... Mass spectrometer, 3 ... Analysis processing control device, 4 ... Data storage device, 5 ... Output device, 11 ...
Analysis control unit, 12: retention time table, 13: correction curve calculation unit, 14: retention time calculation unit, 15: assignment processing unit, 16: quantitative calculation processing unit

Claims (4)

[Claims] 1. A mass spectrometry system for quantitatively analyzing a compound having a plurality of isomers having the same mass number, comprising a chromatography for temporally separating compounds, and a temporal separation by selecting a specific ion and performing said chromatography. SIM
A mass spectrometer for measuring a chromatogram;
A data processing means for obtaining a correction curve for correcting the retention time using an internal standard compound based on the M chromatogram, obtaining the calculated retention time of each isomer of the quantitative compound from the correction curve, assigning the isomer peak, and performing the quantitative calculation A mass spectrometry system comprising: 2. The mass spectrometry system according to claim 1, wherein said data processing means obtains a reference retention time based on a SIM chromatogram of a compound added as an internal standard compound. 3. An output unit for outputting data, wherein the data processing unit outputs the measured SIM chromatogram and a chromatogram pattern of a calculated retention time of each isomer from the output unit. The mass spectrometry system according to claim 1. 4. The data processing means according to claim 1, wherein
4. The mass spectrometry system according to claim 3, wherein assignment information is added to each peak of the chromatogram and output from said output means.