News Column

"Chromatograph Mass Spectrometry Data Processing Device" in Patent Application Approval Process

June 3, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- A patent application by the inventor KAWANA, Shuichi (Kyoto-shi, JP), filed on November 15, 2012, was made available online on May 22, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application is assigned to Shimadzu Corporation.

The following quote was obtained by the news editors from the background information supplied by the inventors: "In GC/MS analysis, various components contained in a test sample are passed through a column and separated over time, and the ions generated from each of the separated components are separated according to their mass-charge ratios (m/z) by a mass spectrograph such as a quadrupole mass filter and detected with a detector. When identifying unknown compounds contained in a sample, scan measurements of prescribed mass ranges (m/z ranges) are ordinarily executed repeatedly in MS, and a mass spectrum is created for each of the scan measurements. A graph in which the intensity determined by adding all of the ion intensities in each mass spectrum is plotted over time is a total ion current chromatogram (TIC), and a graph in which attention is focused on ions having certain mass-charge ratios and the intensities of these ions are plotted over time is an extracted ion chromatogram (EIC).

"When assaying a compound contained in a sample by GC/MS analysis or LC/MS analysis, the ions characterizing the compound are typically determined to be quantitative ions (also called target ions), and quantitative values--that is, the component content or concentration--are calculated from the chromatogram peaks appearing in the vicinity of the retention time of the target compound in an EIC of the quantitative ions obtained by means of actual measurements. Ions corresponding to a peak for which the signal intensity is highest in a typical mass spectrum of the compound are ordinarily selected as quantitative ions.

"Although the quantitative ions described above are ions which characterize each compound, various contaminants may be included in an actual sample, and components may overlap due to insufficient component separation in the previous stage of GC or LC as a result of inappropriate analytical conditions. In such cases, it is sometimes difficult to confirm from chromatogram peaks of quantitative ions alone whether the peaks indeed originate from the target compound. In such cases, ions having a different mass-charge ratio characterizing the compound are selected as confirmation ions separately from the quantitative ions, and it is confirmed--that is, identified--that the chromatogram peaks of the quantitative ions originate from the target compound using the relative ratio (hereafter called the 'confirmation ion ratio') of the signal intensity of the confirmation ion peaks and the signal intensity of the quantitative ion peaks in the mass spectrum. In addition, confirmation ions of one type are often insufficient to accurately confirm the quantitative ion peaks of a compound, and it is common for a plurality of types of confirmation ions to be used for a single compound (see Patent Document 1).

"In a conventional device, a confirmation ion ratio found from data obtained by performing mass spectrometry on a standard sample of a target compound is stored in advance in a storage part as an ideal ratio, and an analyst is able to determine whether the confirmation ion ratio of an identified compound is appropriate by comparing the numerical value of the confirmation ion ratio found from data obtained by analyzing the actual sample and the ideal ratio described above. However, such a determination by numerical values is not very efficient and is prone to misjudgment. Moreover, in order for the analyst to determine whether the identification of a compound is appropriate, it is also necessary to visually confirm the shapes and heights of peaks in the EIC, but it is difficult for the analyst to determine whether a peak height is appropriate based on the confirmation ion ratio by simply examining the EIC.

"In particular, in the case of multi-component analysis, it is necessary for the analyst to visually confirm whether peaks in the EIC are appropriate based on the confirmation ion ratio one by one for an enormous number of compounds ranging from several tens to several hundreds of compounds. Therefore, in order to increase the throughput of such an operation, the analyst is required to assess the appropriateness of each compound in a short amount of time, but such an assessment is difficult to make in a short amount of time with the conventional method described above, and there is also a high probability of causing misjudgment and oversight.

"Patent Document 1--Japanese Unexamined Patent Application Publication 2006-189279"

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "The present invention was conceived in light of the problems described above, and its purpose is to provide a chromatograph mass spectrometry data processing device capable of improving operating efficiency by simplifying the operations performed by an analyst and reducing operational mistakes when performing component identification or quantitative analysis by analyzing data collected by means of chromatograph mass spectrometry.

"The present invention, which was conceived in order to solve the problems described above, is a chromatograph mass spectrometry data processing device for creating extracted ion chromatograms (EIC) with respect to specific mass-charge ratios based on data repeatedly collected over time by chromatograph mass spectrometry and displaying the chromatograms on a display screen, the device being provided with:

"a) a standard information storage means for storing the retention times, the mass-charge ratios of quantitative ions and confirmation ions, and standard values of a confirmation ion ratio expressing the ratio of the intensity of confirmation ions to quantitative ions for various components;

"b) a chromatogram display processing means for creating extracted ion chromatograms of the quantitative ions and confirmation ions of the target components based on actual measurement data of the target components designated to be confirmed among the various components stored in the standard information storage means and displaying the chromatograms in an overlapping manner within the boundaries of the same graph; and

"c) an additional display processing means for obtaining standard values of the confirmation ion ratios of the target components corresponding to the confirmation ions for which extracted ion chromatograms are displayed by the chromatogram display processing means from the standard information storage means and graphically displaying information showing the standard values on the displayed extracted ion chromatograms.

"The chromatograph mass spectrometry data processing device of the present invention can be realized by executing a dedicated computer program for realizing functions corresponding to each of the means described above on a general-purpose computer comprising a display part, an operation part (keyboard, pointing device, or the like), and the like.

"In addition, in the chromatograph mass spectrometry data processing device of the present invention information showing the standard values of confirmation ion ratios of target components should typically be shown as a horizontal line in an overlapping manner in the EIC of quantitative ions and confirmation ions. If there are a plurality of confirmation ions for a single target component, the EICs of the plurality of confirmation ions should be displayed in an overlapping manner with different line colors, for example, and the standard values of the confirmation ion ratios corresponding to each of the confirmation ions should also be similarly displayed in an overlapping manner with different line colors.

"Moreover, in the chromatograph mass spectrometry data processing device of the present invention, an analyst or the like should select components to be identified or components for which content is to be confirmed from among the various components stored in the standard information storage means in advance and create a table in which these components are registered so that the analyst can select target components by designating arbitrary components from the table.

"If the selected target components are components which have been automatically identified using the retention time, the similarity of mass spectrum patterns, the confirmation ion ratio, or the like, the chromatogram display processing means should display an EIC in which the vicinities of peaks identified in the EIC of quantitative ions are magnified. On the other hand, if the selected target components are components which have not been automatically identified, the peaks closest to the retention times of the target components in the EIC of quantitative ions should be considered to be chromatogram peaks corresponding to those components, and an EIC in which the vicinities of the peaks are magnified should be displayed.

"With the chromatograph mass spectrometry data processing device of the present invention, it becomes possible to confirm the peak waveforms originating from target components appearing in an EIC of the confirmation ions of the target components and the ideal intensity ratios of the confirmation ions at a glance within the boundaries of the same graph. Accordingly, the analyst can intuitively and quickly determine whether the peak heights of confirmation ions is approximately the same as the standard value of the confirmation ion ratio. In addition, since the waveform shapes of the peaks of quantitative ions or confirmation ions of target components demonstrated by actual measurements can also be confirmed, it is also possible to simultaneously determine the deformation of peak waveforms caused by the overlapping of non-target components such as contaminants. As a result, when performing operations such as the confirmation of whether target components are present in a sample or the identification of components contained in a sample, the confirmation operation performed visually by the analyst is simplified, which improves the operating efficiency, and the reliability of the results is also improved due to the reduction of operating mistakes.

"Further, in the chromatograph mass spectrometry data processing device of the present invention, it is preferable for the additional display processing means to be configured so as to graphically display information showing a permissible intensity range around the standard values of the confirmation ion ratios on the displayed extracted ion chromatograms. With such a configuration, it is possible to even more simply determine whether the peak heights of confirmation ions fall within a permissible range around the standard values of the confirmation ion ratios.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a schematic block diagram of an embodiment of a GC-MS system containing the data processing device of the present invention.

"FIG. 2 is a schematic diagram showing the data collection operation and the obtained data in the GC-MS system of this embodiment.

"FIG. 3 is a flowchart showing an example of the procedure of the confirmation operation for identifying components in the GC-MS system of this embodiment.

"FIG. 4 is a schematic diagram showing an example of the display screen in the GC-MS system of this embodiment."

URL and more information on this patent application, see: KAWANA, Shuichi. Chromatograph Mass Spectrometry Data Processing Device. Filed November 15, 2012 and posted May 22, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4697&p=94&f=G&l=50&d=PG01&S1=20140515.PD.&OS=PD/20140515&RS=PD/20140515

Keywords for this news article include: Shimadzu Corporation, Information Technology, Information and Data Storage, Information and Data Processing.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Information Technology Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters