JP2666838B2 - Quantitative analysis method using gas chromatography mass spectrometer - Google Patents

Description

The present invention relates to a method for quantitatively analyzing a sample whose content is unknown using a gas chromatography mass spectrometer. (B) Conventional technology and its problems In general, as a method for performing quantitative analysis of a sample using a gas chromatography mass spectrometer, there is a conventional method using a mass chromatograph (MC). This is a computer-assisted analysis method, in which mass scans are repeated at regular time intervals on a sample with an unknown content to measure mass spectra, and then analyzed from hundreds of mass spectra on the obtained sample. Time variation of the ion intensity of a specific mass number of the substance to be created as a mass chromatogram, and the area of each peak of the mass chromatogram,
A quantitative value of each substance contained in the sample is calculated from a calibration curve previously obtained for the substance. By the way, in order to perform quantitative analysis based on such a mass chromatogram, first, it is necessary to identify a substance contained in a sample. For this identification, an absolute retention time method is used, in which a standard retention time is set from retention time data accumulated for various standard substances, and the substance is uniquely identified by a peak falling within the allowable range of the standard retention time. And a relative retention time method for performing identification by correcting a deviation of the retention time due to a change in analysis conditions. However, in both methods, the retention time from the injection of the sample into the gas chromatograph until the peak of the substance appears is used as a reference.For example, impurities are mixed into the sample, and the impurities are mixed with the analyte. When the same retention time is indicated, the mass numbers are often similar to each other, so that the two cannot be distinguished. For this reason, the analysis result is a quantitative value including impurities, which causes inconvenience such as poor reliability of the analysis. Moreover, analysts are accustomed to injecting samples into the gas chromatograph,
The retention time often fluctuates due to unfamiliarity, etc.In addition, in the absolute retention time method and the relative retention time method, it is necessary to change the identification conditions, that is, the standard retention time, the allowable range, with the change of the analysis conditions, For these reasons, the analysis operation was complicated. Further, the present invention has been made in view of such circumstances, even if impurities having the same retention time as the analyte to be mixed into the sample, it is possible to identify the contamination of the impurities, Moreover, it is an object of the present invention to reliably identify a substance without being affected by a change in retention time, to improve the reliability of an analysis result, and to eliminate the complexity of an analysis operation. (C) Means for Solving the Problems In order to achieve the above object, the present invention applies a gas chromatography mass spectrometer and a computer, and repeats mass scanning for a sample whose content is unknown at regular time intervals. After performing a mass spectrum measurement, a mass chromatogram for a specific mass number is created based on the measured mass spectrum of the sample, and the quantitative analysis of the sample is performed based on the created mass chromatograph. Select the mass spectrum data corresponding to the peak top position indicating the specific mass number of the created mass chromatogram, and compare it with the mass spectrum data obtained for various known substances including the selected mass spectrum data To determine the similarity between the two data, identify the substances contained in the sample from this similarity, and identify And to perform a quantitative analysis of materials. (D) Embodiment FIG. 1 is a block diagram of an analyzer applied to carry out the method of the present invention. In the figure, 1 is a gas chromatography mass spectrometer (GC / MS), 2 is a computer, 4 is a CPU of the computer 2, 6 is an internal memory constituting the computer 2, 8 is a gas chromatography mass spectrometer 1 and the computer 2 Interface to combine
Reference numeral 10 denotes an external storage device, and reference numeral 12 denotes an output device such as a CRT display. Next, a method of the present invention to which the above-described analyzer is applied will be described. First, a mass spectrum of a substance whose components and concentrations are known in advance is repeatedly measured by a gas chromatography mass spectrometer 1 at predetermined time intervals over a predetermined mass range to measure a mass spectrum. Then, the measured mass spectrum data is temporarily stored in the internal memory 6 via the interface 8 and the CPU 4. Next, the mass spectrum data stored in the internal memory 6 is read out by the CPU 4, a mass number suitable for quantification of the substance is specified, and a mass chromatogram showing the relationship of the time change of the ion intensity is created. The above operation is performed for various known substances. Outputs the data of the mass chromatogram of each known substance created in this way.
When it is sent to 12, a mass chromatogram as shown in FIG. 2 is displayed. FIG. 2 shows a display example when a mass chromatogram is created for three types of known substances A, B, and C. And each known substance (substances A, B, C in this example)
The data of the mass spectrum (see FIG. 3) corresponding to the position of the peak top of the mass chromatogram obtained for is selected, and this data is transferred from the internal memory 6 to the external storage device 10 via the CPU 4 and stored. . Further, a calibration curve is created from the relationship between the peak area and the concentration of the mass chromatogram obtained by changing the concentration of each known substance, and the data of the calibration curve is stored in the external storage device 10. Next, when it is desired to perform a quantitative analysis of the sample whose content is unknown, for example, for the substance C, the sample is analyzed using the gas chromatography mass spectrometer 1 in the same manner as when the mass chromatogram is measured for the known substance. The mass scan is repeated at regular intervals to measure the mass spectrum, and then the mass number is specified with reference to the mass chromatogram of the known substance in FIG. 2 to create a mass chromatogram of the substance contained in the sample. . The mass chromatogram of the sample thus prepared shows a profile as shown in FIG. FIG. 4 shows a display example when a mass chromatogram is created for four types of substances H, I, J, and K. Next, the mass spectrum data at the peak top position of the known substance C already stored in the external storage device 10 and each of the mass chromatograms of the substances (in the above example, the substances H, I, J, and K). The similarity of the data is obtained by successively comparing the data of the mass spectrum corresponding to the position of the peak top. This similarity (SI) is determined, for example, by the following equation. SI = MSW / ASW where ASW is the integrated value obtained by multiplying all the ion intensities of the mass spectrum of the known substance by the weighting factor according to the mass number, and MSW is the mass spectrum of the substance contained in the sample Is an integrated value obtained by multiplying each ion intensity when a peak existing corresponding to the mass number of a known substance is selected from the above by a weighting coefficient corresponding to the mass number. For example, when the similarity of the mass spectrum at the peak top of the substance J to the mass spectrum of the substance C is obtained, and the similarity is equal to or more than the reference value, the substance J is identified as the known substance C. In this case, if the sample contains an impurity having the same retention time as that of the substance J, the similarity is equal to or less than the reference value, so that the inconvenience of calculating the quantitative value including the impurity is avoided. You. Then, the peak area of the identified substance J is determined, and the quantitative value of the substance J contained in the sample is obtained from this value and the calibration curve stored in the external storage device 10. Note that, in the present invention, the case where the mass spectrum is measured by applying GC / MS has been described.However, even when peak identification is performed for a GC / FT-IR in which a gas chromatograph and an infrared spectroscopic analyzer are combined, It is possible to apply the method of the present invention. (E) Effect As described above, according to the present invention, even when an impurity having the same retention time as the substance to be analyzed is mixed in the sample, the contamination of the impurity can be identified, and the variation in the retention time is affected. Since it is not performed, the substance can be identified reliably. Therefore, excellent effects such as improvement in reliability of the analysis result and elimination of complexity of the analysis operation are exhibited.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an analyzer applied to carry out the method of the present invention, FIG. 2 is an explanatory diagram showing a mass chromatogram of a known substance, and FIG. FIG. 4 is an explanatory diagram showing a mass spectrum at each peak top of the mass chromatogram, and FIG. 4 is an explanatory diagram showing a mass chromatogram of a sample whose content is unknown. 1 ... gas chromatography mass spectrometer, 2 ... computer, 10 ... external storage device.

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) Reference "Chromatographia"                 7 [9] (1974) 502                 "Analytical Chemi               story "45 [7] (1973)               1083

Claims (1)

(57) [Claims] Applying a gas chromatography mass spectrometer and a computer, repeatedly performing mass scanning on a sample whose content is unknown at regular time intervals, measuring a mass spectrum, and then determining a specific mass number based on the measured mass spectrum of the sample. In preparing a mass chromatogram and performing quantitative analysis of the sample based on the mass chromatogram prepared, a mass chromatogram prepared in advance in the same manner as the sample whose content is unknown for various known substances in advance The mass spectrum data corresponding to the position of the peak top is obtained in advance, and the mass spectrum data corresponding to each peak top position of the mass chromatogram created for the sample whose content is unknown is selected. The mass spectrum data is obtained from mass spectra obtained for various known substances in advance. Quantitative analysis using a gas chromatography mass spectrometer characterized by determining the similarity between the two data by comparing it with the spectrum data, identifying the substance contained in the sample from this similarity, and performing quantitative analysis on the identified substance. Analysis method.