WO2018112834A1 - 基于四极杆线性离子阱串联质谱仪器的离子分离检测方法 - Google Patents

基于四极杆线性离子阱串联质谱仪器的离子分离检测方法 Download PDF

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WO2018112834A1
WO2018112834A1 PCT/CN2016/111501 CN2016111501W WO2018112834A1 WO 2018112834 A1 WO2018112834 A1 WO 2018112834A1 CN 2016111501 W CN2016111501 W CN 2016111501W WO 2018112834 A1 WO2018112834 A1 WO 2018112834A1
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ion
ions
quadrupole
ion trap
mass spectrometer
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PCT/CN2016/111501
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English (en)
French (fr)
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熊行创
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江游
黄泽建
龚晓云
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中国计量科学研究院
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Priority to CN201680089567.8A priority Critical patent/CN110291614B/zh
Priority to PCT/CN2016/111501 priority patent/WO2018112834A1/zh
Publication of WO2018112834A1 publication Critical patent/WO2018112834A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/622—Ion mobility spectrometry
    • G01N27/623—Ion mobility spectrometry combined with mass spectrometry
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons

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  • the invention relates to a method for qualitative and quantitative operation of a target substance based on a quadrupole linear ion trap tandem mass spectrometer, in particular to an operation method for efficiently selecting a reaction monitoring of a target substance.
  • Mass spectrometry is to ionize matter particles (atoms, molecules) into ions, and to achieve mass-to-charge ratio separation by spatial position, time sequence, etc., by appropriate stable or changing electric or magnetic fields, and to measure the intensity for qualitative, Analytical method for quantitative analysis. Because mass spectrometry directly measures material particles and has high sensitivity, high resolution, high throughput and high applicability, mass spectrometry plays an important role in modern science and technology. With the development of life sciences, environmental sciences, medical sciences, and food safety, national security, international anti-terrorism, new drug research and development, and clinical testing, mass spectrometers have become one of the fastest growing analytical instruments. In particular, the emergence of chromatography/mass spectrometry and related instruments, because of its high separation function for complex matrices and high sensitivity of detection, is highly favored and even indispensable in the above fields.
  • the mass analyzer is a component of a mass spectrometer that can detect ions separated by mass-to-charge ratio (mass/charge number).
  • the mass analyzer can be divided into a magnetic field mass analyzer, a quadrupole mass analyzer (Quadrupole for short), a linear ion trap/orbit trap mass analyzer (Ion Trap, IT for short), and a time-of-flight mass analyzer (Time of Fight, Referred to as TOF) and so on.
  • the matrix is more and more complex (the background detection interference is getting more and more serious), the target analyte concentration is getting lower and lower, the sensitivity is getting higher and higher, the detection limit is getting lower and lower, and the quantitative detection is Accuracy is getting higher and higher.
  • Mass spectrometers with a single mass analyzer are increasingly difficult to meet the development needs of the trend.
  • tandem mass spectrometers In order to achieve better analytical performance, different or identical mass analyzers are often connected in series. Such mass spectrometers are tandem mass spectrometers.
  • the current mainstream new mass spectrometer products in the world are mainly tandem mass spectrometry.
  • triple quadrupole mass spectrometer QQQ
  • dual pressure linear ion trap mass spectrometer for qualitative analysis
  • quadrupole orbital trap mass analyzer for biological protein analysis
  • Thermo's QE, Fusion quadrupole time-of-flight tandem mass spectrometer
  • IT-TOF ion trap time-of-flight tandem mass spectrometer
  • TOF-TOF quadrupole time-of-flight tandem mass spectrometer
  • QQQ quadrupole linear ion trap tandem mass spectrometer
  • the linear ion trap (LIT) is then isolated from the measured ion in the linear ion trap, and then the ion to be detected is fragmented by collision-induced dissociation to obtain its daughter ion, and its daughter ion is used as the characteristic ion of the measured ion. (for quasi-determinism), then analyze the signal intensity of the characteristic ion to obtain quantitative information of the measured ion.
  • the quadrupole (Q) is used to screen the ions of interest (counted as m).
  • the ions other than (m- ⁇ m ⁇ m+ ⁇ m) are excluded, but also a small amount of ions (m- ⁇ m ⁇ m+ ⁇ m) can enter the LIT, and the m ions that can enter may be 100% of the screening operation.
  • the "ultra-trace" substance m in complex matrices is so low in absolute content in LIT that it is difficult to detect.
  • the present invention proposes an ion separation detecting method based on a quadrupole linear ion trap tandem mass spectrometer.
  • An ion separation detection method based on a quadrupole linear ion trap tandem mass spectrometer includes the following steps:
  • the matrix ions are shaped by the pre-quadrupole and transmitted to the quadrupole mass filter system, and the width of the sampling window is selected to be m- ⁇ m ⁇ m+ ⁇ m by adjusting the RF voltage loaded on the quadrupole system.
  • the ions in the sampling window are transmitted to the rear quadrupole by the filter quadrupole system, and other ions are eliminated; the ions in the sampling window range are shaped by the rear quadrupole and continue to enter the linear ion trap;
  • step S206 performing step S205 for 100ms to 10s, closing the ion gate, and stopping the transmission of the matrix ions to the quadrupole system;
  • the pair of ions m and its special product ions m1 are further included between step S206 and step S207.
  • Fine isolation of m2 Compared with the width of the sampling window of the ion m and its special product ions m1 and m2 in step S205, the sampling window of the ion m and its special product ions m1 and m2 is again reduced, and the width of the reduced sampling window is respectively It is m- ⁇ m2 to m+ ⁇ m2, m1- ⁇ m2 to m1+ ⁇ m2, and m2- ⁇ m2 to m2+ ⁇ m2.
  • a single frequency signal is included in the waveform of the alternating voltage, the single frequency signal being at the same frequency as the ion m in the X direction, thereby resonating with the ion m.
  • the amplitude of the single frequency signal is greater than the amplitude of the motion of the ion m in the X direction, while the amplitude of the single frequency signal is less than the amplitude of the vibration of the waveform of the alternating voltage in the step 205 in the X direction.
  • the value range of ⁇ m in step S204 is: 3amu ⁇ m ⁇ 10amu.
  • the value range of ⁇ m1 in step 205 is: 1 amu ⁇ ⁇ m1 ⁇ 4 amu.
  • the value range of ⁇ m2 in step S205 is: ⁇ m2 ⁇ 2amu.
  • the radio frequency voltage loaded on the quadrupole system is a radio frequency voltage corresponding to the electric charge q of the corresponding ion m being between 0.1 and 0.908; the q value is calculated according to the following formula:
  • V RF is the RF voltage amplitude
  • ⁇ is the frequency value of the RF voltage
  • r is the shortest distance from the center of the ion trap to the X or Y direction electrode
  • z is the ion trap center point The distance to the end cap in the Z direction.
  • the radio frequency voltage applied to the quadrupole system is a radio frequency voltage corresponding to a charge amount q of the corresponding ion m being between 0.2 and 0.4.
  • the RF voltage loaded on the quadrupole system is a radio frequency voltage corresponding to a charge amount q of the corresponding ion m at 0.25.
  • the ion separation detecting method of the present invention has at least the following advantages:
  • the ion separation detection method based on the quadrupole linear ion trap tandem mass spectrometer first screens the sample ions of interest (monitored ions) with quadrupoles, injects the monitored ions into the linear ion trap, and the monitored ions enter the linearity.
  • the ion trap uses edge collision to induce dissociation of the monitored ions, while segregating and retaining the fragment ions (the characteristic ions of the monitored ions) after being detected by the monitored ions.
  • Such a long-term operation series can efficiently enrich the fragments of the monitored ions. Splitting ions to achieve efficient detection of monitored ions.
  • This test method is especially suitable for qualitative and quantitative analysis of trace substances (targets of interest) in complex matrices.
  • FIG. 1 is a schematic diagram of a mass spectrometer of a quadrupole linear ion trap tandem mass spectrometer
  • FIG. 2 is a schematic flow chart of an ion separation detecting method based on a quadrupole linear ion trap tandem mass spectrometer according to the present invention
  • Fig. 3 is a schematic diagram showing the voltage spectrum applied to the ion trap electrode by simultaneously performing isolation and inducing cracking of the measured ions and enriching characteristic ions.
  • a quadrupole linear ion trap tandem mass spectrometer mass spectrometer device as shown in FIG. 1 includes an ion source 101, an ion guiding system (including an ion introduction line 111 and an ion guiding line 112), a pre-quadrupole 121, and a filter.
  • the multi-stage gradient vacuum system 110 includes a plurality of vacuum sections in which the air pressure is sequentially lowered, each vacuum section is provided with a through hole, and the ion introduction system includes an ion introduction line 111 communicating with the ion source 101 and a multi-stage gradient vacuum system 110.
  • the ion guiding line 112 in each vacuum zone.
  • the port of the ion guiding line 112 is being connected to the through hole in which the vacuum section is connected to the adjacent vacuum section, and the linear ion trap 131 is located in the last stage vacuum section 120 of the multi-stage gradient vacuum system 110,
  • the buffer gas injection system 161 injects a buffer gas (inert gas) into the linear ion trap 131 through the gas conduit 141, and the detector 151 includes two detectors 151 symmetrically disposed on both sides of the ion trap 131.
  • the air pressure of the last stage vacuum section of the multi-stage gradient vacuum system 110 is usually 10 -5 Torr, and a certain small hole (such as the through hole 114) is communicated in each vacuum section, and the multi-stage gradient vacuum system 110 is ion-imported.
  • the line 111 is in communication with the standard atmospheric pressure section 100.
  • the ions from the ion source 101 enter the multi-stage gradient vacuum system 110 through the ion introduction line 111, and the ion guiding line 112 is responsible for the ions being transferred within the multi-stage gradient vacuum system 110.
  • the vacuum zones of the multi-stage gradient vacuum system 110 are responsible for obtaining a vacuum by molecular pumps of different pumping speeds, such as molecular pump 119 and molecular pump 129, or a composite multi-stage vacuum pump.
  • An ion lens 113 is disposed at an end of the ion guiding line 112 disposed in the first-stage vacuum section of the vacuum section where the linear ion trap 131 is located, and the ion lens 113 is responsible for controlling the transport of ions to the rear end, which is called an ion gate.
  • the pre-quadrupole 121 also known as the ion transmission shaping system, is responsible for the ion shaping from the ion transport system, smoothly entering the filter quadrupole 122, and the filter quadrupole 122 only allows (m- ⁇ m ⁇ m+ ⁇ m) The window section ions pass (other ions do not pass) and enter the rear quadrupole 123. Further, the rear quadrupole 123 pairs the (m- ⁇ m ⁇ m+ ⁇ m) window section ion shaping, and smoothly passes through the ion trap front end cover 132 into the linear ion trap 131.
  • Front end cover 132 and the rear end cover 133 have a hole of about 2 mm in the center, the hole of the front end cover 132 is for the introduction of ions, and the hole of the rear end cover 133 is symmetrical with the hole of the front end cover 132.
  • Front end cover 132, ion trap 131 and rear end cover 133 form a complete linear ion trap mass analyzer system that conducts and applies a corresponding DC voltage.
  • a radio frequency voltage (calculated as V RF ) is applied to the pair of electrodes in the X and Y directions of the ion trap 131, and a high frequency alternating current (calculated as AC) is applied in the X direction.
  • the combination of these voltages forms an electric field that enables storage, separation, collision of ions and molecules, and ion eviction.
  • the four symmetric electrodes of the ion trap 131 can appropriately increase the length of the electrode in the Z direction while ensuring that the electric fields in the X and Y directions are constant.
  • a portion of the side of the ion trap 131 corresponding to the detector 151 is provided with an ion detecting slit, and the ion detecting slit is a slit of about 30 mm * 0.25 mm.
  • the flow of the ion separation detecting method based on the quadrupole linear ion trap tandem mass spectrometer shown in FIG. 2 corresponds to the following steps S201-S208.
  • the ion separation detection method based on a quadrupole linear ion trap tandem mass spectrometer includes the following steps:
  • the matrix ions are shaped by the pre-quadrupole and transmitted to the quadrupole mass filter system, and the width of the sampling window is selected to be m- ⁇ m ⁇ m+ ⁇ m by adjusting the RF voltage loaded on the quadrupole system.
  • the ions in the sampling window are transmitted to the rear quadrupole by the filter quadrupole system, and other ions are eliminated; the ions in the sampling window range are shaped by the rear quadrupole and continue to enter the linear ion trap;
  • step S205 the coarse isolation operation of three ions (m, m1, m2) is simultaneously performed, thereby ensuring that the detected ions and the sub ions are not lost, and other non-interest ions (other non-interest ions) are also excluded.
  • the total amount is far more than the measured ions.
  • the ions in the ion trap should not be saturated, which is convenient for normal operation.
  • ⁇ m ⁇ 10 amu ensures that the product ions (m1, m2) are not within (m - ⁇ m - m + ⁇ m). Normally, the product ions that m induces cleavage are not within (m-10 amu ⁇ m + 10 amu).
  • the coarse separation refers to ⁇ m>2amu, and the fine separation refers to ⁇ m ⁇ 1.5amu; m has a variety of product ions, depending on the structure of m, what is the fragmentation, what kind of product ions are, and the product ions m1 and m2 are The fragment ion of m is therefore less than m.
  • step S206 performing step S205 for 100ms to 10s, closing the ion gate, and stopping the transmission of the matrix ions to the quadrupole system;
  • step S206 When the signal of the ion m and its special product ions m1 and m2 in the linear ion trap is inconspicuous with respect to the other ion relative signals, the fine of the ion m and its special product ions m1 and m2 is further included between step S206 and step S207.
  • the sampling window of the ion m and its special product ions m1 and m2 in step S205 is again reduced, and the width of the reduced sampling window is m- ⁇ m2 to m+ ⁇ m2, m1- ⁇ m2 to m1+ ⁇ m2, and m2- ⁇ m2 to m2+ ⁇ m2.
  • a single frequency signal is included in the waveform of the alternating voltage, the single frequency signal being at the same frequency as the ion m in the X direction, thereby resonating with the ion m.
  • the amplitude of the single frequency signal is greater than the amplitude of the motion of the ion m in the X direction, while the amplitude of the single frequency signal is less than the amplitude of the vibration of the waveform of the alternating voltage in the step 205 in the X direction.
  • the value range of ⁇ m in step S204 is: 3amu ⁇ ⁇ m ⁇ 10 amu.
  • step 205 the value range of ⁇ m1 is: 1amu ⁇ ⁇ m1 ⁇ 4amu.
  • the value range of ⁇ m2 in step S205 is: ⁇ m2 ⁇ 2 amu.
  • the RF voltage loaded on the quadrupole system is the RF voltage corresponding to the charge q of the corresponding ion m at 0.25.
  • the characteristic ion (m1, m2) of the measured ion (m) can be stably moved in the ion trap by the quadrupole electric field force (when the RF voltage is V RF , the q value of m1 and m2 is less than 0.908);
  • V RF is the RF voltage amplitude
  • ⁇ is the frequency value of the RF voltage
  • r is the shortest distance from the center of the ion trap to the X or Y direction electrode
  • z is the ion trap center point The distance to the end cap in the Z direction.
  • Fig. 3 is a schematic diagram showing the voltage spectrum applied to the ion trap electrode by simultaneously performing isolation and inducing cracking of the measured ions and enriching characteristic ions.
  • the alternating voltage of a specific waveform (WF) applied to the X-direction electrode of the ion trap 131 is precisely controllable.
  • the frequency component of WF contains a frequency component of 10 kHz to 500 kHz (frequency interval is not more than 500 Hz), but does not include the frequency of movement of ions m, m1, and m2 to be isolated in the X direction, so that other ions, ie, windows, can be Width (m - ⁇ m1 ⁇ m + ⁇ m1) (corresponding to the frequency window F (m + ⁇ m1) ⁇ F (m - ⁇ m1)), (m1 - ⁇ m2 ⁇ m + ⁇ m2) (corresponding to the frequency window F (m1 + ⁇ m2) ⁇ F (m1 - ⁇ m2)), (m2 - ⁇ m2 - m2 + ⁇ m2) (corresponding to ions outside the frequency window F (m2 + ⁇ m2) - F (m - ⁇ m
  • the specific waveform (WF) contains a single-frequency signal for induced fragmentation of the measured ion (m), which is FCD-m.
  • the Fcid-m and the measured ion (m) move at the same frequency in the X direction, thereby forming a resonance.
  • the difference is to evict the resonance for the purpose of isolating the designated ions.
  • the amplitude of the induced fragmentation signal is small (relative to the amplitude of the ejected resonance signal), and only the detected ions (m) collide with the buffer gas molecules in the ion trap to generate heat, thereby
  • the chemical bond cleavage of the ions produces ion fragments (which are daughter ions m1, m2) and neutral molecules.

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Abstract

一种基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，是先用四极杆筛选出感兴趣的样品离子(被监测离子)，将被监测离子注入线性离子阱(131)，等被监测离子进入线性离子阱(131)，采用边碰撞诱导解离被监测离子、边隔离保留被监测离子碎裂后的子离子(被监测离子的特征离子)，如此长时间的操作系列，能够高效富集被监测离子的碎裂子离子，从而实现对被监测离子的高效检测。该方法尤其适用于复杂基质中痕量物质(感兴趣目标物)的定性定量分析。

Description

基于四极杆线性离子阱串联质谱仪器的离子分离检测方法 技术领域
本发明涉及基于四极杆线性离子阱串联质谱仪器对目标物质定性定量操作方法，特别是有关于目标物质高效选择反应监测的操作方法。
背景技术
质谱分析方法是将物质粒子(原子、分子)电离成离子，并通过适当的稳定或变化的电场或磁场将它们按空间位置、时间顺序等实现质荷比分离，并检测其强度来作定性、定量分析的分析方法。由于质谱分析方法直接测量物质粒子，并且具有高灵敏、高分辨、高通量和高适用性的特性，使得质谱技术在现代科学技术中的地位举足轻重。随着生命科学、环境科学、医药科学等学科的发展，以及食品安全、国家安全、国际反恐、新药研发、临床检测的需要，质谱仪已成为需求量增长速度最快的分析仪器之一。尤其是色谱/质谱联用技术和相关仪器的出现，因其对复杂基质的高分离功能和检测的高灵敏度，更是在上述各领域倍受青睐，甚至不可或缺。
质量分析器是质谱仪器中将离子依照质荷比(质量/电荷数)分离出来可以检测的部件。质量分析器可以分为磁场质量分析器、四极杆质量分析器(Quadrupole简称Q)、线性离子阱/轨道阱质量分析器(Ion Trap，简称IT)、飞行时间质量分析器(Time of Fight，简称TOF)等等。
当前，物质分析和检测需求趋势，基质越来越复杂(本底检测干扰越来越严重)，要求目标检测物浓度越来越低、灵敏度越来越高、检测限越来越低、定量检测准确度越来越高。单一质量分析器的质谱仪越来越难以满足趋势的发展需求。
为了实现更好的分析性能，往往将不同或相同的质量分析器串联起来，这样的质谱为串联质谱仪。当前世界上主流的新质谱仪产品主要是串联质谱。例如：用于定量分析的三重四极杆质谱仪(QQQ)，定性分析的双压线性离子阱质谱仪(专利号US8198580B2)、用于生物蛋白分析的四极杆轨道阱质量分析器(Thermo的QE、Fusion)、四极杆飞行时间串联质谱仪(Q-TOF)、离子阱飞行时间串联质谱仪(IT-TOF)、TOF-TOF等等。
对于复杂基质中痕量物质的选择反应监测有着强劲的需求，QQQ是非常好的仪器；然而对于复杂基质中“超痕量”物质(浓度低于10-12g/g)，QQQ 就难以胜任。如是，市场上提出的四极杆线性离子阱串联质谱仪器(Q-LIT，或称为QTrap)，试图通过首先用四极杆(Q)筛选感兴趣的目标离子(被测离子)，大量注入线性离子阱(LIT)，然后在线性离子阱中再隔离出被测离子，再通过碰撞诱导解离操作将被测离子碎裂从而获得其子离子，将其子离子作为被测离子的特征离子(用于准确定性)，然后分析该特征离子的信号强度从而获得被测离子的定量信息。
然后，在具体仪器中存在着一系列难以克服的矛盾使得Q-LIT难以实现对复杂基质中“超痕量”物质的分析。例如：通过四极杆(Q)筛选感兴趣的离子(计为m)，为了准确定性，Q在筛选时允许通过离子的窗口宽度2Δm往往设置为：2Δm＜＝4amu。那么不仅把(m-Δm～m+Δm)外的离子排除在外，也使得只有少量的(m-Δm～m+Δm)的离子能够进入LIT，能够进入的m离子可能是不筛选操作的百分之一。特别是复杂基质中“超痕量”物质m，其在LIT中绝对含量还是很少，以至于难以被监测到。
当然，针对这种难题，增加LIT的离子容量(很难增加20倍以上)，通过多次离子注入等方式都是可能的解决方案，但是实现的复杂度和难度过大而收效甚微。因此，即使时市场上出现了Q-LIT(或QTrap)的仪器，但没有达到预期的成效，其应用难以普及。
如何能够实现QTrap对复杂基质中“超痕量”物质的选择反应高效监测，真正发挥Q加Trap的串联功能，这是QTrap质谱仪器需要解决的重要技术问题。
发明内容
为了解决上述问题，本发明提出一种基于四极杆线性离子阱串联质谱仪器的离子分离检测方法。
本发明的目的是通过以下技术方案实现的：
一种基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，包括如下步骤：
S201，清洁离子源、离子管道和离子阱，调整质谱仪的真空系统和电气系统的参变量至初始状态，然后在离子源内装载好被测试样品基质；
S202，将被测试样品基质离子化，产生包括被测样品离子m在内的多个基质离子；
S203，打开离子门，基质离子被离子传输系统持续传输到四极杆系统；
S204，基质离子被预四极杆整形后传输到四极杆滤质系统，通过调整加载在四极杆系统上的射频电压，选取采样窗口的宽度为m-Δm～m+Δm，使所述采样窗口范围内的离子被滤质四极杆系统传到后四极杆，其他离子排除掉；所述采样窗口范围内的离子被后四极杆整形后，持续进入线性离子阱；
S205，缩小所述采样窗口的宽度为m-Δm1～m+Δm1，在线性离子阱中对离子m进行持续的粗隔离；同时对离子m进行持续粗隔离的同时对其进行诱导裂解，产生包括离子m的特征子离子m1和m2在内的多个产物离子；同时保持施加在线性离子阱X方向电极和Y方向电极上的射频电压与加载到四极杆系统上的射频电压相同，调节施加在X方向电极上的交流电压，所述交流电压的波形的频率成分包含10kHz-500kHz的频率成分；所述频率的间隔不大于500Hz，同时所述频率中不包含离子m及其特征子离子m1和m2在X方向的运动频率，从而使窗口宽度在m-Δm1～m+Δm1范围、m1-Δm1～m+Δm1范围和m2-Δm1～m2+Δm1范围以外的其他离子在X方向上与所述频率发生共振从而排出线性离子阱，达到在线性离子阱内储存离子m及其特征子离子m1和m2的目的；
S206，执行步骤S205持续100ms～10s，关闭离子门，基质离子停止传输到四极杆系统；
S207，在线性离子阱内对离子m及其特殊子离子m1和m2进行离子分离检测，获得离子m及其特殊子离子m1和m2的信号强度信息；
S208，停止扫描，排空离子阱中所有离子。
优选地，当线性离子阱内的离子m及其特殊子离子m1和m2的信号相对其他离子相对信号不明显时，在步骤S206和步骤S207之间还包括对离子m及其特殊子离子m1和m2的精细隔离：相对于步骤S205中离子m及其特殊子离子m1和m2的采样窗口的宽度，再次缩小离子m及其特殊子离子m1和m2的采样窗口，缩小后的采样窗口的宽度分别为m-Δm2～m+Δm2、m1-Δm2～m1+Δm2、m2-Δm2～m2+Δm2。
优选地，在交流电压的波形中包含一个单频率信号，所述单频率信号与离子m在X方向的运动频率相同，从而与离子m形成共振。
优选地，所述单频率信号的幅度大于离子m在X方向的运动的幅度，同时单频率信号的幅度小于步骤205中所述交流电压的波形在X方向的振动幅度。
优选地，步骤S204中Δm的取值范围为：3amu＜Δm＜10amu。
优选地，步骤205中Δm1的取值范围为：1amu＜Δm1＜4amu。
优选地，步骤S205中Δm2的取值范围为：Δm2＜2amu。
优选地，加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.1～0.908时所对应的的射频电压；所述q值按下列公式计算：
Figure PCTCN2016111501-appb-000001
在式(1)中，
Figure PCTCN2016111501-appb-000002
为被测离子的质荷比倒数，VRF为射频电压幅值，Ω为射频电压的频率值，r为离子阱中心点到X方向或Y方向电极的最短距离值，z为离子阱中心点到Z方向端盖的距离值。
优选地，所述加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.2～0.4时所对应的的射频电压。
优选地，所述加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.25时所对应的的射频电压。
与现有技术相比，本发明的离子分离检测方法至少具有以下优点：
本发明基于四极杆线性离子阱串联质谱仪器的离子分离检测方法先用四极杆筛选出感兴趣的样品离子(被监测离子)，将被监测离子注入线性离子阱，等被监测离子进入线性离子阱，采用边碰撞诱导解离被监测离子、边隔离保留被监测离子碎裂后的子离子(被监测离子的特征离子)，如此长时间的操作系列，能够高效富集被监测离子的碎裂子离子，从而实现对被监测离子的高效检测。本检测方法尤其适用于复杂基质中痕量物质(感兴趣目标物)的定性定量分析。
附图说明
图1为一种四极杆线性离子阱串联质谱仪器质谱装置示意图；
图2为本发明基于四极杆线性离子阱串联质谱仪器的离子分离检测方法流程示意图；
图3为同时实现隔离并诱导裂解被测离子、富集特征子离子施加在离子阱电极上电压频谱示意图。
具体实施方式
下面结合附图1-3以及以下具体实施例对本发明的方法进行详细说明。
如图1所示的四极杆线性离子阱串联质谱仪器质谱装置，包括离子源101、离子导引系统(包含离子导入管路111和离子导引管路112)、预四极杆121、滤质四极杆122、后四极杆123、线性离子阱131、多级梯度真空系统110、用于检测离子的检测器151、通过气体导管141向线性离子阱131内注入缓冲气的缓冲气注入系统161。
所述多级梯度真空系统110包括气压依次降低的多个真空区间，各真空区间开有通孔，离子导入系统包括与离子源101连通的离子导入管路111和设置在多级梯度真空系统110各真空区内的离子导引管路112。所述离子导引管路112的端口正对其所在真空区间与相邻真空区间连接的通孔，所述线性离子阱131位于多级梯度真空系统110的最后一级真空区间120内，所述缓冲气注入系统161通过气体导管141向线性离子阱131内注入缓冲气(惰性气体)，所述检测器151包括对称设置在离子阱131两侧的两个检测器151。
所述多级梯度真空系统110的最后一级真空区间的气压通常为10-5托(Torr)，各真空区间存在一定小孔(如通孔114)相通，多级梯度真空系统110通过离子导入管路111与标准大气压区间100相连通，离子源101发出的离子通过离子导入管路111进入到多级梯度真空系统110，离子导引管路112负责离子在多级梯度真空系统110内传递。多级梯度真空系统110的各真空区间由不同抽速的分子泵(如分子泵119和分子泵129，也可以是复合的多级真空泵)负责获得真空。
在线性离子阱131所在真空区间上一级真空区间内设置的离子导引管路112的末端设置有离子透镜113，离子透镜113负责控制离子向后端传输，称为离子门。
预四极杆121，也称为离子传输整形系统，负责将从离子传输系统的离子整形，顺利进入滤质四极杆122，滤质四极杆122仅仅让(m-Δm～m+Δm)窗口区间离子通过(其他离子不通过)，进入后四极杆123。再由后四极杆123对(m-Δm～m+Δm)窗口区间离子整形，顺利通过离子阱前端盖132进入线性离子阱131。
前端盖132和后端盖133中心均有一个约2mm的孔，前端盖132的孔是用于离子的导入，后端盖133的孔与前端盖132的孔对应对称。前端盖132、离子阱131和后端盖133组成完整的线性离子阱质量分析器系统，均导电并施加相应直流电压。在离子阱131的X、Y方向电极对上施加射频电压(计为VRF)，在X 方向上施加高频交流电(计为AC)。这些电压的组合实施形成电场，实现离子的存储、分离、离子与分子的碰撞、离子逐出等操作。为了实现存储更多的离子，可将离子阱131的4个对称电极在保证X、Y方向电场不变的情况下适当增加Z方向的电极长度。
所述离子阱131侧面对应设置有检测器151的部分开有离子检测狭缝，该离子检测狭缝约为30mm*0.25mm的狭缝。
如图2所示，图2中所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法流程对应以下步骤S201-S208。
所述基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，包括如下步骤：
S201，清洁离子源、离子管道和离子阱，调整质谱仪的真空系统和电气系统的参变量至初始状态，然后在离子源内装载好被测试样品基质；
S202，将被测试样品基质离子化，产生包括被测样品离子m在内的多个基质离子；
S203，打开离子门，基质离子被离子传输系统持续传输到四极杆系统；
S204，基质离子被预四极杆整形后传输到四极杆滤质系统，通过调整加载在四极杆系统上的射频电压，选取采样窗口的宽度为m-Δm～m+Δm，使所述采样窗口范围内的离子被滤质四极杆系统传到后四极杆，其他离子排除掉；所述采样窗口范围内的离子被后四极杆整形后，持续进入线性离子阱；
S205，缩小所述采样窗口的宽度为m-Δm1～m+Δm1，在线性离子阱中对离子m进行持续的粗隔离；同时对离子m进行持续粗隔离的同时对其进行诱导裂解，产生包括离子m的特征子离子m1和m2在内的多个产物离子；同时保持施加在线性离子阱X方向电极和Y方向电极上的射频电压与加载到四极杆系统上的射频电压相同，调节施加在X方向电极上的交流电压，所述交流电压的波形的频率成分包含10kHz-500kHz的频率成分；所述频率的间隔不大于500Hz，同时所述频率中不包含离子m及其特征子离子m1和m2在X方向的运动频率，从而使窗口宽度在m-Δm1～m+Δm1范围、m1-Δm1～m+Δm1范围和m2-Δm1～m2+Δm1范围以外的其他离子在X方向上与所述频率发生共振从而排出线性离子阱，达到在线性离子阱内储存离子m及其特征子离子m1和m2的目的；
在步骤S205中同时执行3个离子(m、m1、m2)的粗隔离操作，既确保被检测离子及子离子不损失，也排除了其他非感兴趣离子(其他非感兴趣离子的 总量远多于被测离子，被逐出后离子阱内离子不宜饱和，便于正常工作)；隔离和精确诱导裂解同时发生，通常是先隔离再诱导裂解，也就是把非感兴趣离子全部逐出离子阱后再诱导裂解，保证诱导裂解产生的子离子为兴趣离子(m)的产物，而不是背景里的相同质荷比的离子。本方法之所以可以隔离和精确诱导裂解同时执行，是因为前面的四极杆滤质系统仅仅让(m-Δm～m+Δm)进入离子阱，背景很干净。当然，Δm＜10amu，确保子离子(m1、m2)不在(m-Δm～m+Δm)之内。通常情况下，m诱导裂解的产物离子不在(m-10amu～m+10amu)之内。
粗隔离指Δm＞2amu，精隔离指Δm＜1.5amu；m的产物离子多种多样，取决于m的结构，碎裂成什么样子，就有什么样子的产物离子，产物离子m1和m2由于是m的碎片离子，所以小于m。
S206，执行步骤S205持续100ms～10s，关闭离子门，基质离子停止传输到四极杆系统；
S207，在线性离子阱内对离子m及其特殊子离子m1和m2进行离子分离检测，获得离子m及其特殊子离子m1和m2的信号强度信息；
S208，停止扫描，排空离子阱中所有离子。
当线性离子阱内的离子m及其特殊子离子m1和m2的信号相对其他离子相对信号不明显时，在步骤S206和步骤S207之间还包括对离子m及其特殊子离子m1和m2的精细隔离：相对于步骤S205中离子m及其特殊子离子m1和m2的采样窗口的宽度，再次缩小离子m及其特殊子离子m1和m2的采样窗口，缩小后的采样窗口的宽度分别为m-Δm2～m+Δm2、m1-Δm2～m1+Δm2、m2-Δm2～m2+Δm2。
在交流电压的波形中包含一个单频率信号，所述单频率信号与离子m在X方向的运动频率相同，从而与离子m形成共振。
所述单频率信号的幅度大于离子m在X方向的运动的幅度，同时单频率信号的幅度小于步骤205中所述交流电压的波形在X方向的振动幅度。
步骤S204中Δm的取值范围为：3amu＜Δm＜10amu。
步骤205中Δm1的取值范围为：1amu＜Δm1＜4amu。
步骤S205中Δm2的取值范围为：Δm2＜2amu。
加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.25时所对应的的射频电压。
q值的选择要兼顾3个方面的因素：
1)被测离子(m)的诱导碎裂点(首先要求能够诱导碎裂，再看诱导碎裂效果)q取值范围往往：0.2-0.4(VRF保持不变，即对于某离子m的q值保持不变，将离子阱X方向电极的选择共振交流电压设置到频率与m离子在X方向的频率相同，从而形成小幅共振，让m/z与缓冲惰性分子发生碰撞产生热量从而使m离子的化学键断裂产生离子碎片，即诱导碎裂)；
2)被测离子(m)的特征子离子(m1、m2)能够在被四极电场力束缚在离子阱中稳定运动(在射频电压为VRF时，m1、m2的q值小于0.908)；
3)被测离子(m)注入离子阱被捕获的效率，单位时间内捕获被测离子(m)数量越多越好。
其中，所述q值按下列公式计算：
Figure PCTCN2016111501-appb-000003
在式(1)中，
Figure PCTCN2016111501-appb-000004
为被测离子的质荷比倒数，VRF为射频电压幅值，Ω为射频电压的频率值，r为离子阱中心点到X方向或Y方向电极的最短距离值，z为离子阱中心点到Z方向端盖的距离值。
图3为同时实现隔离并诱导裂解被测离子、富集特征子离子施加在离子阱电极上电压频谱示意图。
如图3所示，施加在离子阱131的X方向电极上特定波形(WF)的交流电压，其频率成分精确可控。通常情况下，WF的频率成分包含10kHz～500kHz的频率成分(频率间隔不大于500Hz)，但是不包含要隔离的离子m、m1和m2在X方向的运动频率，这样才能将其他离子，即窗口宽度(m-Δm1～m+Δm1)(对应频率窗口F(m+Δm1)～F(m-Δm1))、(m1-Δm2～m+Δm2)(对应频率窗口F(m1+Δm2)～F(m1-Δm2))、(m2-Δm2～m2+Δm2)(对应频率窗口F(m2+Δm2)～F(m2-Δm2))外的离子在X方向发生共振，从而逐出离子阱131。
同时特定波形(WF)包含一个单频率的信号，用于对被测离子(m)进行诱导碎裂，该单频率计为Fcid-m。Fcid-m与被测离子(m)在X方向运动频率相同，从而形成共振。区别以隔离指定离子为目的逐出共振，该诱导碎裂信号幅度很小(相对于逐出共振信号幅度)，仅仅让被测离子(m)与离子阱内缓冲气分子发生碰撞产生热量从而使离子的化学键断裂产生离子碎片(为子离子m1、m2)和中性分子。
以上所述，仅为本发明较佳的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应该以权利要求书的保护范围为准。

Claims (10)

  1. 一种基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，包括如下步骤：
    S201，清洁离子源、离子管道和离子阱，调整质谱仪的真空系统和电气系统的参变量至初始状态，然后在离子源内装载好被测试样品基质；
    S202，将被测试样品基质离子化，产生包括被测样品离子m在内的多个基质离子；
    S203，打开离子门，基质离子被离子传输系统持续传输到四极杆系统；
    S204，基质离子被预四极杆整形后传输到四极杆滤质系统，通过调整加载在四极杆系统上的射频电压，选取采样窗口的宽度为m-Δm～m+Δm，使所述采样窗口范围内的离子被滤质四极杆系统传到后四极杆，其他离子排除掉；所述采样窗口范围内的离子被后四极杆整形后，持续进入线性离子阱；
    S205，缩小所述采样窗口的宽度为m-Δm1～m+Δm1，在线性离子阱中对离子m进行持续的粗隔离；同时对离子m进行持续粗隔离的同时对其进行诱导裂解，产生包括离子m的特征子离子m1和m2在内的多个产物离子；同时保持施加在线性离子阱X方向电极和Y方向电极上的射频电压与加载到四极杆系统上的射频电压相同，调节施加在X方向电极上的交流电压，所述交流电压的波形的频率成分包含10kHz～500kHz的频率成分；所述频率的间隔不大于500HZ，同时所述频率中不包含离子m及其特征子离子m1和m2在X方向的运动频率，从而使窗口宽度在m-Δm1～m+Δm1范围、m1-Δm1～m+Δm1范围和m2-Δm1～m2+Δm1范围以外的其他离子在X方向上与所述频率发生共振从而排出线性离子阱，达到在线性离子阱内储存离子m及其特征子离子m1和m2的目的；
    S206，执行步骤S205持续100ms～10s，关闭离子门，基质离子停止传输到四极杆系统；
    S207，在线性离子阱内对离子m及其特殊子离子m1和m2进行离子分离检测，获得离子m及其特殊子离子m1和m2的信号强度信息；
    S208，停止扫描，排空离子阱中所有离子。
  2. 根据权利要求1所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，当线性离子阱内的离子m及其特殊子离子m1和m2的信号相对其他离子相对信号不明显时，在步骤S206和步骤S207之间还包括对离子m及其特殊子离子m1和m2的精细隔离：相对于步骤S205中离子m及其特殊子离子m1和m2的采样窗口的宽度，再次缩小离子m及其特殊子离 子m1和m2的采样窗口，缩小后的采样窗口的宽度分别为m-Δm2～m+Δm2、m1-Δm2～m1+Δm2、m2-Δm2～m2+Δm2。
  3. 根据权利要求1所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，在交流电压的波形中包含一个单频率信号，所述单频率信号与离子m在X方向的运动频率相同，从而与离子m形成共振。
  4. 根据权利要求3所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，所述单频率信号的幅度大于离子m在X方向的运动的幅度，同时单频率信号的幅度小于步骤205中所述交流电压的波形在X方向的振动幅度。
  5. 根据权利要求1所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，步骤S204中Δm的取值范围为：3amu＜Δm＜10amu。
  6. 根据权利要求1所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，步骤205中Δm1的取值范围为：1amu＜Δm1＜4amu。
  7. 根据权利要求1所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，步骤S205中Δm2的取值范围为：Δm2＜2amu。
  8. 根据权利要求1所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.1～0.908时所对应的的射频电压；所述q值按下列公式计算：
    Figure PCTCN2016111501-appb-100001
    在式(1)中，
    Figure PCTCN2016111501-appb-100002
    为被测离子的质荷比倒数，VRF为射频电压幅值，Ω为射频电压的频率值，r为离子阱中心点到X方向或Y方向电极的最短距离值，z为离子阱中心点到Z方向端盖的距离值。
  9. 根据权利要求8所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，所述加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.2～0.4时所对应的的射频电压。
  10. 根据权利要求9所述的基于四极杆线性离子阱串联质谱仪器的离子分离检测方法，其特征在于，所述加载在四级杆系统上的射频电压为对应离子m的电荷量q处于0.25时所对应的的射频电压。
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