Method for improving dynamic range of spectrogram of mass spectrometer

Abstract

The invention provides a method for improving the dynamic range of a spectrogram of a mass spectrometer, and the method specifically comprises the steps: selecting a working mode according to the ion concentration, selecting a first working mode when the ion concentration is lower, and selecting a second working mode when the ion concentration is higher: in the first working mode, ions linearly enter a first detector; and in the second working mode, the ions are deflected through the deflection lens, and the deflection angle of the ions is adjusted, so that different numbers of ions enter the off-axis second detector. The method has the advantages of large dynamic range and the like.

Description

Technical Field

[0001] The present invention relates to mass spectrometry technology, and particularly to a method for improving the dynamic range of a mass spectrometer spectrum. Background Art

[0002] In quantitative testing of a mass spectrometer, sometimes full-range detection from ppt level to ppm level is encountered, and the detection dynamic range of a normal mass spectrometer is difficult to meet the conditions of such applications. For example, in the analysis of soil pollutants, there may be trace metal pollutants such as Ni and Cu at the ppt level, as well as elements such as Na and Ca at hundreds of ppm. During conventional analysis, the dynamic range of the detector is difficult to reach the detection from ppt to ppm level. If dilution is performed, trace elements may not be detected. When the sample amount is too small, batch detection may not be possible.

[0003] To solve the above problems, the general solution is: during detection of low concentrations, normal detection is carried out; when high concentrations are reached, the solution is reprocessed, diluted, and remeasured. The disadvantages of this solution are as follows: 1. Small dynamic range; 2. Complicated operation, dilution is required, especially for samples with unknown concentrations. Summary of the Invention

[0004] To solve the deficiencies in the above prior art solutions, the present invention provides a method for improving the dynamic range of a mass spectrometer spectrum.

[0005] The object of the present invention is achieved by the following technical solutions: A method for improving the dynamic range of a mass spectrometer spectrum, specifically: Select the working mode according to the ion concentration. When the ion concentration is low, select the first working mode; when the ion concentration is high, select the second working mode: In the first working mode, ions enter the first detector linearly; In the second working mode, ions are deflected by a deflection lens, and the deflection angle of the ions is adjusted so that different numbers of ions enter the off-axis second detector.

[0006] Compared with the prior art, the present invention has the following beneficial effects: 1. Large dynamic range; For samples with a large ion concentration, dilution of the ion concentration is achieved by using different deflection angles of the ions, thereby realizing the detection of elements with concentrations from ppt level to ppm level; 2. Fast and convenient; There is no need to dilute the sample, and ion detection is fast and convenient. Brief Description of the Drawings

[0007] With reference to the accompanying drawings, the disclosure of the present invention will become more readily understandable. It is easily understood by those skilled in the art that these drawings are merely used to illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention. In the figures: Figure 1 is a schematic structural diagram of a mass spectrometer according to the present invention. Detailed implementation manners

[0008] Figure 1 The following description and examples describe alternative specific implementation manners of the present invention to teach those skilled in the art how to implement and reproduce the present invention. For the purpose of teaching the technical solutions of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art should understand that variations or substitutions derived from these specific implementation manners will fall within the scope of the present invention. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following alternative specific implementation manners and is only defined by the claims and their equivalents.

[0009] Example 1

[0010] A method for improving the dynamic range of a mass spectrometer spectrum in an embodiment of the present invention is specifically as follows: Select a working mode according to the ion concentration. When the ion concentration is low, select the first working mode, and when the ion concentration is high, select the second working mode: In the first working mode, as Figure 1 shown, ions enter the first detector 11 linearly. In the second working mode, the ions are deflected by the deflection lens 41, and the deflection angle of the ions is adjusted so that different numbers of ions enter the off-axis second detector 12, achieving dilution of the ion concentration.

[0011] To improve the detection consistency, further, the method further includes a calibration stage: Ions of the same concentration enter the first detector 11 and the second detector 12 respectively, and the mass spectrometer is calibrated using the differences between the detectors.

[0012] To deflect the ions, further, the greater the negative potential applied to the deflection lens 41, the greater the deflection angle of the ions, and the more ions enter the second detector 12.

[0013] When the ion concentration is low, the ions sequentially pass through the mass analyzer 21, the entrance lens 31, and the extraction lens 32 and enter the first detector 11; When the ion concentration is high, the ions sequentially pass through the mass analyzer 21, the entrance lens 31, and the deflection lens 41 and enter the second detector 12.

[0014] To better achieve ion deflection, further, the deflection lens 41 includes: A first cylindrical lens 42 disposed between the entrance lens 31 and the extraction lens 32; A cylindrical lens 43 disposed below the line connecting the first cylindrical lens 42 and the extraction lens 32; A second cylindrical lens 44. When negative voltages are applied to the first cylindrical lens 42, the cylindrical lens 43, and the second cylindrical lens 44, ions pass through the first cylindrical lens 511, then bypass the cylindrical lens 43 and deflect, and then pass through the second cylindrical lens 44 and are received by the second detector 12.

[0015] To achieve deflection, the central axes of the first cylindrical lens 42 and the second cylindrical lens 44 are perpendicular and coplanar, and the central axis of the cylindrical lens 43 is perpendicular to the central axis of the first cylindrical lens 42 respectively.

[0016] Embodiment 2

[0017] An application example of the method for improving the dynamic range of the mass spectrometer spectrum according to Embodiment 1 of the present invention.

[0018] In this application example, as Figure 1 shown, the mass analyzer 21, the entrance lens 31, the extraction lens 32, and the first detector 11 are arranged in sequence along a straight line. The second detector 12 is arranged off-axis. Ions pass through the mass analyzer 21, the entrance lens 31, and the deflection lens 41 in sequence, and the deflected ions enter the second detector 12.

[0019] In the deflection lens 41, the first cylindrical lens 42 is disposed between the entrance lens 31 and the extraction lens 32. The cylindrical lens 43 is disposed below the line connecting the first cylindrical lens 42 and the extraction lens 32. When negative voltages are applied to the first cylindrical lens 42, the cylindrical lens 43, and the second cylindrical lens 44, ions pass through the first cylindrical lens 42, then bypass the cylindrical lens 43 and deflect, and then pass through the second cylindrical lens 44 and are received by the second detector 12. The central axes of the first cylindrical lens 42 and the second cylindrical lens 44 are perpendicular and coplanar, and the central axis of the cylindrical lens 43 is perpendicular to the central axis of the first cylindrical lens 42 respectively.

[0020] The method for improving the dynamic range of the mass spectrometer spectrum according to the embodiment of the present invention is specifically: Set the threshold of the signal volume CPS (count per second) detected by the detector 11 to 4 million (the corresponding solution concentration is generally 10 - 50 ppb, and this concentration value generally cannot be directly determined by the detector). If the detected signal volume is lower than the threshold, it can be considered that the ion concentration is low, and the first working mode is selected; if it is not lower than the threshold, it is considered that the ion concentration is high, and the second working mode is selected: (in this case, the selection of the detection method should be directly determined based on the CPS detected by the first detector). In the first working mode, a negative voltage of -20V is applied to the inlet lens to focus the ions. The potential on the deflection lens 41 is 0V, and a negative voltage of -50V is applied to the extraction lens. The ions emitted from the mass analyzer 21 pass through the inlet lens 31, the first cylindrical lens 42, and the extraction lens 32 in a straight line in sequence and enter the first detector 1 for detection.

[0021] In the second working mode, the potential on the extraction lens is 0V, and a potential of -200 to -600V is applied to the deflection lens 41, and the deflection lens 41 will generate a deflecting force on the ions.

[0022] When the potential on the deflection lens 41 is small, most of the ions are deflected outside the first detector 11 and the second detector 12, and a small part of the ions reach the second detector 12 after deflection. At this time, the ion signal detected by the second detector 12 is low. When the negative potential applied to the deflection lens 41 increases, the deflection angle of the ions gradually increases. When it reaches the optimal value, the vast majority of the ions will be deflected into the second detector 12. Therefore, by adjusting the voltage on the deflection lens 41, different degrees of dilution of the ion concentration detected by the second detector 12 can be achieved.

[0023] Calibration stage: Select the intermediate concentration value and introduce it into the first detector 11 and the second detector 12 respectively. At this time, the detected signal volumes of the two are different, but the concentrations are the same. Cross - calibration is performed on this, which can broaden the dynamic range of the mass spectrometer detection while ensuring linearity.

Claims

1. A method for improving the dynamic range of a mass spectrometer spectrum, specifically: Select the working mode according to the ion concentration. When the ion concentration is low, select the first working mode, and when the ion concentration is high, select the second working mode: In the first working mode, the ions enter the first detector linearly. In the second working mode, the ions are deflected by the deflection lens, and the deflection angle of the ions is adjusted so that different numbers of ions enter the off-axis second detector.

2. The method for improving the dynamic range of a mass spectrometer spectrum according to claim 1, wherein The method further includes a calibration stage: Ions of the same concentration enter the first detector and the second detector respectively, and the mass spectrometer is calibrated using the differences between the detectors.

3. The method for improving the dynamic range of a mass spectrometer spectrum according to claim 1, wherein The greater the negative potential applied to the deflection lens, the greater the ion deflection angle and the more ions enter the second detector.

4. The method for improving the dynamic range of a mass spectrometry spectrum according to claim 1, wherein, Set an ion concentration threshold. Below the threshold is considered low concentration, and not lower than the threshold is considered high concentration.

5. The method for improving the dynamic range of a mass spectrometer spectrum according to claim 1, wherein When the ion concentration is low, the ions sequentially pass through the mass analyzer, the entrance lens, and the extraction lens and enter the first detector. When the ion concentration is high, the ions sequentially pass through the mass analyzer, the entrance lens, and the deflection lens and enter the second detector.

6. The method for improving the dynamic range of a mass spectrometer spectrum according to claim 5, characterized in that, The deflection lens includes: A first cylindrical lens, which is arranged between the entrance lens and the extraction lens; A cylindrical lens, which is arranged below the connection line between the first cylindrical lens and the extraction lens; A second cylindrical lens. When negative voltages are applied to the first cylindrical lens, the cylindrical lens, and the second cylindrical lens, the ions pass through the first cylindrical lens, then deflect around the cylindrical lens, and then pass through the second cylindrical lens and are received by the second detector.

7. The method for improving the dynamic range of a mass spectrometer spectrum according to claim 6, characterized in that, The central axes of the first cylindrical lens and the second cylindrical lens are perpendicular and coplanar, and the central axis of the cylindrical lens is perpendicular to the central axis of the first cylindrical lens respectively.

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