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CN-122000266-A - Quadrupole mass spectrometer capable of inhibiting interference of high-abundance ions on low-mass end

CN122000266ACN 122000266 ACN122000266 ACN 122000266ACN-122000266-A

Abstract

A quadrupole mass spectrometer capable of inhibiting interference of high-abundance ions on a low mass end comprises an ion source, a quadrupole mass analyzer, a first power supply device, a second power supply device and a third power supply device, wherein the ion source comprises an ionization chamber and a filament assembly arranged at an electron inlet of the ionization chamber, the quadrupole mass analyzer is arranged at the downstream of the ion source, the first power supply device is connected with the filament assembly and is used for providing a first direct current voltage capable of controlling electron kinetic energy for the filament assembly, the second power supply device is connected with the quadrupole mass analyzer and is used for providing an alternating voltage capable of scanning from low ion mass number to high ion mass number and a second direct current voltage capable of controlling ion axial kinetic energy for the quadrupole mass analyzer, the third power supply device is connected with the ionization chamber and is used for providing a third voltage capable of controlling electron kinetic energy and ion kinetic energy for the ionization chamber, and the third power supply device is used for applying a first level and a second level to the ionization chamber in a low-mass and high-mass scanning stage respectively, and the first level is lower than the second level. The invention effectively solves the problem that the existing quadrupole mass spectrometer loses the ion screening capability due to the fact that the scanning voltage of the quadrupole is close to zero in the initial stage of mass scanning. The problem often causes a large number of high-abundance and high-quality ions to pass through a quadrupole mass analyzer in a low-quality scanning interval and be detected by a detector, so that a strong interference peak is generated, a target signal is covered, the detector is easy to be saturated instantaneously, and the aging of the detector is accelerated.

Inventors

  • CHENG YUPENG

Assignees

  • 微谱科技(湖州)有限公司

Dates

Publication Date
20260508
Application Date
20260209

Claims (9)

  1. 1. A quadrupole mass spectrometer that suppresses interference of high abundance ions with a low mass end, comprising: an ion source comprising an ionization chamber and a filament assembly disposed at an electron inlet of the ionization chamber, and A quadrupole mass analyzer, the quadrupole mass analyzer is disposed downstream of the ion source; Wherein the filament assembly is connected with a first power supply device which is configured to provide a first direct current voltage capable of controlling electronic kinetic energy for the filament assembly; The quadrupole mass analyzer is connected with a second power supply device, and the second power supply device is configured to provide alternating voltage capable of scanning from low ion mass number to high ion mass number and second direct current voltage capable of controlling the axial kinetic energy of ions for the quadrupole mass analyzer; a third power supply device is connected to the ionization chamber, and is configured to provide a third voltage capable of controlling electron kinetic energy and ion kinetic energy for the ionization chamber; When the alternating voltage applied to the quadrupole mass analyzer by the second power supply device causes the ion mass number scanned by the quadrupole mass analyzer to be lower than a preset ion mass number, the third power supply device applies a first level of a third voltage to the ionization chamber; When the alternating voltage applied to the quadrupole mass analyzer by the second power supply device causes the ion mass number scanned by the quadrupole mass analyzer to be higher than a preset ion mass number, the third power supply device applies a second level of a third voltage to the ionization chamber; the first level is lower than the second level and a timing period of the third voltage is synchronized with a mass scan period of the quadrupole mass analyzer.
  2. 2. The quadrupole mass spectrometer capable of suppressing interference of high-abundance ions on a low mass end according to claim 1, wherein the preset ion mass number is in a range of 0.5amu to 5amu.
  3. 3. The quadrupole mass spectrometer of claim 1, wherein the voltage difference between the second level and the first level is one of 0 v-10 v, 10 v-20 v, 20 v-30 v, 30 v-40 v and 40 v-100 v.
  4. 4. The quadrupole mass spectrometer of claim 1 wherein adjacent ones of the mass scan periods comprise a non-mass scan phase therebetween and the third power supply means applies a third level of a third voltage to the ionization chamber, the third level being lower than the second level.
  5. 5. The quadrupole mass spectrometer of claim 4, wherein the third level and the second level have a voltage difference of one of 0 v-10 v, 10 v-20 v, 20 v-30 v, 30 v-40 v and 40 v-100 v.
  6. 6. The quadrupole mass spectrometer of claim 1, wherein the ionization chamber comprises a cube-shaped ionization chamber body having a through-hole formed along a first direction, the through-hole forming a sample inlet and an ion beam outlet on two surfaces of the ionization chamber body, respectively; Four surfaces of the ionization chamber body in the second direction and the third direction are respectively provided with pits for mounting the filament assembly, and each pit is internally provided with an electronic slit communicated with the through hole; The first direction, the second direction and the third direction are perpendicular to each other in space.
  7. 7. The quadrupole mass spectrometer of claim 6 wherein the filament assembly comprises a filament arm, an electron repeller and a filament holder; The electronic repulsion electrode comprises a first bending metal sheet and a second bending metal sheet, wherein the first bending metal sheet is attached to a first bending surface of the second bending metal sheet after being stacked and detachably and fixedly connected to the upper part of the middle part of the back surface of the filament fixer, and the first bending metal sheet is parallel to a second bending surface of the second bending metal sheet after being stacked and is positioned above the front surface of the filament fixer at a certain distance; grooves are symmetrically formed in two sides of the front face of the filament fixer, two filament arms are detachably and fixedly connected in the grooves respectively, a filament is fixedly connected between the upper ends of the two filament arms, meanwhile, the filament penetrates through the second bending surface of the first bending metal sheet and the second bending surface of the second bending metal sheet, and one filament arm is connected with the electronic repulsion electrode.
  8. 8. The quadrupole mass spectrometer of claim 1, wherein the ion source further comprises an off-axis electrostatic lens assembly disposed between the ionization chamber and the quadrupole mass analyzer, the off-axis electrostatic lens assembly comprising a first deflection lens group, a second deflection lens group, and a third deflection lens group; The first deflection lens group is used for focusing the ion beam which is emitted from the ionization chamber and enters along the central axis and deflecting the ion beam in the direction I, the second deflection lens group is used for receiving and focusing the ion beam from the first deflection lens group and deflecting the ion beam in the direction II, and the third deflection lens group is used for receiving and focusing the ion beam from the second deflection lens group and deflecting the ion beam in the direction III, and the direction III is basically parallel to the central axis of the first deflection lens.
  9. 9. The quadrupole mass spectrometer of claim 1, wherein the quadrupole mass analyzer comprises a quadrupole rod and a quadrupole pre-rod disposed at an end of the quadrupole rod facing the ion source, the quadrupole rod pre-rod configured for focusing and introducing an ion beam into the quadrupole rod, the quadrupole rod configured for mass scanning and screening the ion beam.

Description

Quadrupole mass spectrometer capable of inhibiting interference of high-abundance ions on low-mass end Technical Field The invention relates to the technical field of mass spectrometry, in particular to a quadrupole mass spectrometer capable of inhibiting interference of high-abundance ions on a low-mass end. Background In quadrupole mass spectrometry, the high abundance ion clusters detected at the beginning of the scan are commonly referred to as "zero mass peaks". The peak appears at the position of the mass number close to zero in the mass spectrogram, which can cause serious interference to the detection of the real signal at the low-mass end, even cover the real signal completely, thereby obviously affecting the accuracy and reliability of the analysis result. The four-pole mass spectrometer is used as a core analysis instrument, and the working principle is that a specific radio-frequency voltage and a specific direct-current voltage are applied to four parallel electrode rods to form a dynamically scanned four-pole electric field, so that selective transmission and screening of ions with different mass-to-charge ratios (m/z) are realized. A typical mass scanning process starts with a lower voltage combination and increases linearly with time to achieve periodic scanning from low mass numbers to high mass numbers. However, the existing quadrupole mass spectrometer generally has the problem of serious distortion of low-quality end signals, and the root of the problem is that at the beginning of scanning, the radio-frequency voltage and the direct-current voltage are at extremely low level, and an effective dynamic barrier field cannot be established inside the quadrupole. At this time, the quadrupole loses mass filtering capability and only shows one ion-transport channel without mass selectivity. All ions generated in the ionization source, regardless of their mass, can pass unimpeded through the quadrupole rods, forming a very high intensity signal interference peak, i.e. "zero mass peak", in the low mass region. The high-intensity interference peak can cause a series of negative effects of linkage, which severely restrict the analysis performance of the instrument, including 1, the huge ion flow corresponding to the interference peak is far beyond the linear range of the detector, so that the output current of the detector reaches the upper limit rapidly and is saturated. The detector can recover to a normal working line interval from a saturated state after a certain time, during the recovery period, a real low-quality ion signal immediately following the real low-quality ion signal is severely suppressed, distorted and even completely lost, so that peak shape distortion and quantitative deviation are caused, 2, the tail effect of an interference peak remarkably lifts the baseline noise level of a low-quality area, so that the weak low-abundance and low-quality target ion signal is submerged in noise, the detection sensitivity of an instrument at a low-quality end is greatly reduced, 3, continuous high-current impact can accelerate the aging of key devices such as an electron multiplier and the like, the service life of the key devices is shortened, and 4, the abnormal peak can be mistakenly identified as a characteristic peak of an unknown compound by data processing software, so that a wrong qualitative result is caused. At present, aiming at the technical proposal that a quadrupole mass spectrometer interferes with low-mass end signals due to high-abundance ions in the initial stage of scanning, an evading strategy is mostly adopted, and an effective mechanism for actively blocking ion flow at an ion source is lacked. For example, the tandem mass spectrometer described in patent publication CN103582929a and a method of using the same, which employs a dynamic scanning window strategy, reduces its impact by avoiding interference regions, while this approach alleviates the signal distortion problem to some extent, but at the expense of effective scanning time, reduces overall analysis efficiency. More importantly, the scheme does not inhibit the generation of ions from the source, cannot control the mass of the ion flow entering the quadrupole rods, and untreated ions can continuously accumulate in the ionization chamber to aggravate the degradation of the low-mass-end signal, so that the problem of systematic interference caused by zero mass peak is difficult to fundamentally solve. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, the invention provides the quadrupole mass spectrometer capable of inhi