Adaptive ion detection method

Abstract

The invention relates to a mass spectrum technology, and particularly provides a self-adaptive ion detection method which comprises the following steps: (A1) ions enter a transmission channel to obtain a process induction current of the ions during transmission, and the process induction current is converted into a first voltage V1; receiving the ions by a receiving electrode to obtain an ion bombardment induction current, and converting the ion bombardment induction current into a second voltage V2; (A2) obtaining k = V2 / V1; (A3) if k is less than the first threshold value k1, reducing the ionization time, and returning to the step (A1) until k reaches the first threshold value k1; if the first threshold value cannot be reached, entering the step (A4); if k is not less than a first threshold value k1, entering a step (A5); (A4) reducing the bias voltage connected with the receiving electrode, and returning to the step (A1) until k reaches a first threshold value k1; and (A5) carrying out mass spectrometry. The method has the advantages of accurate detection and the like, and is applied to ion detection.

Description

Technical Field

[0001] The present invention relates to mass spectrometry technology, and in particular to an adaptive ion detection method. Background Art

[0002] The Faraday cup is a detector used to measure the incident intensity of charged particles. The measured current can be used to determine the number of incident electrons or ions. When ions pass through one or more suppression grids and enter the cup, a current is generated, which is converted into a voltage and then amplified and recorded.

[0003] The commonly used Faraday cup adopts a cylindrical structure. The bottom of the tube is used to receive electrons, the edge of the tube is used for shielding, and the front end is used for ion introduction. It uses a mesh electrode or a metal plate with holes in the middle, and the outside of the tube also needs to be insulated.

[0004] In the practical application of the Faraday cup, the following technical problems arise.

[0005] 1. When a large number of ions enter the cup, it will cause a large number of ion secondary scattering, causing the cup to heat up seriously, forming a lot of noise, drowning out the effective signal and reducing the detection sensitivity.

[0006] 2. Excessive ion intensity will significantly increase the energy discharge time of the amplifier circuit, thereby reducing the signal resolution.

[0007] To solve the above problems, the main method currently is to cool the Faraday cup detector to reduce the noise caused by electron bombardment of the cup body, thereby improving the detection sensitivity, but the cooling components will make it larger and the power consumption will increase significantly. In addition, it still cannot solve the problem of prolonged energy discharge time and poor signal resolution caused by excessive ions. Summary of the invention

[0008] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides an adaptive ion detection method.

[0009] The objective of the present invention is achieved through the following technical solutions: An adaptive ion detection method, the detection method comprising the following steps: (A1) Ions enter the transmission channel, the process induced current of the ions during transmission is obtained, and converted into the first voltage V 1 ; The ions are received by the receiving electrode, and the ion bombardment induced current is obtained and converted into a second voltage V 2 ; (A2) Get k = V 2 / V 1 ; (A3) If k is less than the first threshold k 1, reduce the ionization time and return to step (A1) until k reaches the first threshold k 1 ; If the first threshold cannot be reached, go to step (A4); If k is not less than the first threshold k 1 , proceed to step (A5); (A4) Reduce the bias voltage connected to the receiving electrode and return to step (A1) until k reaches the first threshold k 1 ; (A5) Perform mass spectrometry analysis.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The ion transmission process induced current and ion bombardment induced current are detected simultaneously. The ionization time and bias voltage are adjusted by the transmission induced current, thereby controlling the ion bombardment induced current, reducing the noise generated by overheating, and solving the problem of reduced resolution caused by too long energy discharge time. The peak tailing caused by the slow energy release of the Faraday cup is solved, the mass spectrum peak shape is improved, and the response intensity is doubled. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The disclosure of the present invention will become easier to understand with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. In the drawings: Figure 1 is a schematic flow chart of an adaptive ion detection method according to the present invention; Figure 2 is a schematic diagram corresponding to the first voltage and the radio frequency voltage according to the present invention; Figure 3 is a schematic diagram corresponding to the second voltage and the radio frequency voltage according to the present invention; Figure 4 2 is a schematic diagram of spectrum voltage according to the present invention. DETAILED DESCRIPTION

[0012] Figure 1-Figure 4 The following description describes optional specific embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or replacements derived from these specific embodiments will be within the scope of the present invention. Those skilled in the art will 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 optional specific embodiments, but is only limited by the claims and their equivalents.

[0013] Example 1.

[0014] An adaptive ion detection method according to an embodiment of the present invention is as follows: Figure 1 As shown, the following steps are included: (A1) Ions enter the cylindrical transmission channel for transmission, and the process induced current of the ions during transmission is obtained and converted into a first voltage V 1 .

[0015] The ions are received by the receiving electrode, and the ion bombardment induced current is obtained and converted into a second voltage V 2 ; The receiving electrode is respectively connected to the signal amplification circuit and the bias voltage circuit.

[0016] (A2) Get k = V 2 / V 1 .

[0017] (A3) If k is less than the first threshold k 1 , reduce the ionization time and return to step (A1) until k reaches the first threshold k 1 ; If the first threshold cannot be reached, go to step (A4).

[0018] If k is not less than the first threshold k 1 , go to step (A5).

[0019] (A4) Reduce the bias voltage connected to the receiving electrode and return to step (A1) until k reaches the first threshold k 1 .

[0020] (A5) Perform mass spectrometry analysis.

[0021] In order to accurately obtain the induced current, further, a spiral metal wire is wound on the outer side of the transmission channel, so as to obtain the process induced current during transmission.

[0022] In order to achieve insulation, further, the ion transmission channel is formed in a cylindrical component, the radial outer side of the receiving electrode is an insulating layer, and the radial outer edge of the insulating layer is connected to the end of the cylindrical component.

[0023] In order to set the threshold scientifically, further, the first threshold k 1 =m·k 3 , k 3 is the stable value of k and m is the coefficient.

[0024] In order to accurately obtain k 3 , further, k 3 The way to obtain is: For any sample, gradually increase the ionization time to obtain different k = V 2 / V 1 , k changes from normal fluctuation to abnormal fluctuation, and the k value of normal fluctuation is taken as k3 .

[0025] In order to solve the peak tailing caused by the slow release of Faraday cup energy and double the response intensity, the detection method further includes: Perform blank sample analysis and adjust the transmitted RF voltage V 0i , and obtain the RF voltage V 0i The first voltage V 10i and the second voltage V 20i ; Perform sample analysis and adjust the transmitted RF voltage V 0i , and obtain the RF voltage V 0i The first voltage V 11i and the second voltage V 21i ; Get the spectrum voltage V fi =(V 21i -V 20i )+(V 10i -V 11i ), i=1,2···N, N is an integer not less than 2.

[0026] Example 2.

[0027] An application example of the adaptive ion detection method according to embodiment 1 of the present invention.

[0028] In this application example, Figure 1 As shown, the ion detection method includes the following steps: An ion transmission channel is formed in the metal cylindrical component, and the radial outer side of the disc-shaped receiving electrode is an annular insulating layer, and the radial outer edge of the insulating layer is connected to the end of the cylindrical component, so that it becomes a component with one end open and one end closed. The receiving electrode is respectively connected to the second signal amplification circuit and the bias voltage circuit. The metal wire is spirally wound on the outer side of the cylindrical component and connected to the first signal amplification circuit.

[0029] (A0) For any sample, the ionized ions enter the ion transmission channel for transmission, and the metal wire obtains the process induced current of the ions during transmission, which is converted into the first voltage V by the first signal amplification circuit. 1 .

[0030] The ions are received by the receiving electrode, and the ion bombardment induced current is obtained, which is converted into a second voltage V by the second signal amplification circuit. 2 .

[0031] Gradually increase the ionization time to obtain different k=V 2 / V 1 , k changes from normal fluctuation to abnormal fluctuation, and the k value of normal fluctuation is taken as k 3, in this embodiment it is 15.

[0032] (A1) The sample to be tested is ionized, and the ions enter the ion transmission channel for transmission. The metal wire obtains the process induced current of the ions during transmission, and is converted into a first voltage V by the first signal amplification circuit. 1 .

[0033] The ions are received by the receiving electrode, and the ion bombardment induced current is obtained, which is converted into a second voltage V by the second signal amplification circuit. 2 .

[0034] (A2) Get k = V 2 / V 1 .

[0035] (A3) If k is less than the first threshold k 1 =0.9 k 3 , reduce the ionization time by the step size (5% of the maximum ionization time) and return to step (A1) until k reaches the first threshold k 1 =0.9 k 3 If k cannot reach the first threshold value simply by reducing the ionization time, proceed to step (A4).

[0036] If k is not less than the first threshold, go to step (A5).

[0037] (A4) Reduce the bias voltage connected to the receiving electrode according to the step size (10% of the maximum bias voltage), and return to step (A1) until k reaches the first threshold.

[0038] (A5) Perform mass spectrometry analysis.

[0039] In this embodiment, a blank sample analysis is performed and the transmitted RF voltage V is adjusted. 0i , and obtain the RF voltage V 0i The first voltage V 10i and the second voltage V 20i .

[0040] Perform sample analysis and adjust the transmitted RF voltage V 0i , and obtain the RF voltage V 0i The first voltage V 11i ,like Figure 2 As shown, and the second voltage V 21i ,like Figure 3 shown.

[0041] Get the spectrum voltage V fi =(V 21i -V 20i )+(V 10i -V 11i), i=1,2···N, N is an integer not less than 2, the spectrum is as follows Figure 4 As shown, the mass spectrum peak shape is significantly improved.

Claims

1. An adaptive ion detection method, characterized in that: The detection method comprises the following steps: (A1) Ions enter the transmission channel, and the process induced current of the ions during transmission is obtained and converted into a first voltage V1; The ions are received by the receiving electrode, and the ion bombardment induced current is obtained and converted into a second voltage V2; (A2) Obtain k = V2 / V1; (A3) If k is less than the first threshold k1, reduce the ionization time and return to step (A1) until k reaches the first threshold k1; if it cannot reach the first threshold, go to step (A4); If k is not less than the first threshold k1, proceed to step (A5); (A4) reducing the bias voltage connected to the receiving electrode, and returning to step (A1) until k reaches a first threshold k1; (A5) Perform mass spectrometry analysis.

2. The detection method according to claim 1, characterized in that: A spiral metal wire is wound on the outside of the transmission channel to obtain a process induced current during transmission.

3. The detection method according to claim 1, characterized in that: Reduce the ionization time and bias voltage in steps.

4. The detection method according to claim 3, characterized in that: The step size was 5% of the maximum ionization time and 10% of the maximum bias voltage.

5. The detection method according to claim 1, characterized in that: The ion transmission channel is formed in the cylindrical component, the radial outer side of the receiving electrode is an insulating layer, and the radial outer edge of the insulating layer is connected to the end of the cylindrical component.

6. The detection method according to claim 1, characterized in that: The receiving electrodes are respectively connected to a signal amplifying circuit and a bias voltage circuit.

7. The detection method according to claim 1, characterized in that: The first threshold k1=m·k3, k3 is a stable value of k, and m is a coefficient.

8. The detection method according to claim 7, characterized in that: The way to obtain k3 is: For any sample, the ionization time is gradually increased to obtain different k= V2 / V1, k changes from normal fluctuation to abnormal fluctuation, and the k value of normal fluctuation is taken as k3.

9. The detection method according to claim 7, characterized in that: m=0.9。 10. The detection method according to claim 1, characterized in that: The detection method further comprises: Perform blank sample analysis and adjust the transmitted RF voltage V 0i , and obtain the RF voltage V 0i The first voltage V 10i and the second voltage V 20i ; Perform sample analysis and adjust the transmitted RF voltage V 0i , and obtain the RF voltage V 0i The first voltage V 11i and the second voltage V 21i ; Get the spectrum voltage V fi =(V 21i -V 20i )+(V 10i -V 11i ), i=1,2···N, N is an integer not less than 2.

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