CN114527187A - Ion analysis apparatus and method - Google Patents
Ion analysis apparatus and method Download PDFInfo
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- CN114527187A CN114527187A CN202011202646.XA CN202011202646A CN114527187A CN 114527187 A CN114527187 A CN 114527187A CN 202011202646 A CN202011202646 A CN 202011202646A CN 114527187 A CN114527187 A CN 114527187A
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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
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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
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- 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
- H01J49/426—Methods for controlling ions
Abstract
The present invention provides an ion analysis apparatus, including: a first ion source for providing analyte ions; a second ion source for providing auxiliary ions; the auxiliary ions have a polarity opposite to the analyte ions, the ion cloud of the auxiliary ions and the ion cloud of the analyte ions are spatially coincident, and at least a portion of the analyte ions do not chemically react with the auxiliary ions; an ion analyzer for analyzing analyte ions; ion transport means located between the first ion source and the ion analyser for transporting analyte ions into the ion analyser and rejecting auxiliary ions into the ion analyser. The present invention can reduce or eliminate space charge effects between a large number of analyte ions, thereby improving ion analysis performance, such as sensitivity, resolution, etc., subject to such conditions.
Description
Technical Field
The present invention relates to the field of ion analysis technology, and in particular, to an ion analysis apparatus and method.
Background
Space charge effect, refers to the spatial distribution due to charge force interactions between charged particles. Space charge effects play an important role in mass spectrometry instruments. Since mass spectrometers are mostly used to analyze ions of a single polarity, space charge effects manifest as a broad ion cloud distribution due to coulombic repulsion between like-charged ions when the number of ions is considerable.
Ion cloud broadening due to space charge effects often degrades the performance of mass spectrometers. For example, for the electrospray ionization source widely used in mass spectrometers at present, the size of the spray beam is greatly expanded due to the space charge effect, and the sampling efficiency is reduced accordingly, that is, the number of ions entering the mass spectrometer through a sampling port or a vacuum port (such as a capillary tube, a conical hole, etc.) with a certain fixed size is greatly reduced. This effect is more pronounced for higher charge density applications, such as nanoliter spray ion sources. Furthermore, in the internal space of the vacuum interface, for example, in the capillary tube that is used for desorbing the solvent and serves as the vacuum interface, ions are easily expanded outward due to the space charge effect and neutralized by charges on the wall surface of the capillary tube, and the ion state cannot be maintained for mass spectrometry. Ion beam broadening due to charge repulsion after the vacuum interface can cause difficulties in ion trapping and focusing.
For a mass spectrometer or ion mobility spectrometer operating in a pulsed mode, broadening of the ion cloud due to space charge effects can not only affect sensitivity, but also reduce the resolution of the analysis. Since the resolution of such pulsed analyzers is directly related to the initial broadening of the ion beam. Although in some devices the effect of initial broadening can be reduced by some compensation measures, spatial broadening still leaves analytical performance beyond the physical limits under these conditions.
In US6359286, an ion beam of opposite polarity is introduced to reduce the space charge effect in the original ion beam, and the method can be applied in the field of high energy ion implantation (ionization). Jon Willams also introduced both positive and negative ions into the Paul ion trap to reduce space charge effects in the ion trap and thus observed an increase in Mass spectrum peak shape and resolution (Rapid Communications in Mass Spectrometry, Vol.7,380-382 (1993)). However, no one has used a similar concept for improving the sensitivity of the mass spectrometer, and the species, operation, and the like of the ions of two polarities are not specifically defined and explained.
Disclosure of Invention
The detector arrangement of the mass spectrometer, which is usually set and optimized for positive/negative ions respectively, is difficult to analyze for positive/negative ions simultaneously; and, the simultaneous existence of positive and negative ions is easy to generate neutralization reaction, so that the ions are not electrified any more, and the mass spectrometry cannot be carried out continuously. Therefore, to increase the sensitivity of the mass spectrometer, the skilled person would not normally think of this being achieved by introducing positive/negative ions into the mass spectrometry process.
In view of the above problems, it is an object of the present invention to provide an ion analysis apparatus and an ion analysis method, which are mainly used for a mass spectrometer, and can reduce or eliminate space charge effects between a large number of analyte ions, thereby improving ion analysis performance (such as sensitivity, resolution, etc.) under the limitation of the conditions.
To achieve the above and other related objects, the present invention provides an ion analysis apparatus comprising:
a first ion source for providing analyte ions;
a second ion source for providing auxiliary ions;
the auxiliary ions have a polarity opposite to the analyte ions, the ion cloud of the auxiliary ions and the ion cloud of the analyte ions are spatially coincident, and at least a portion of the analyte ions do not chemically react with the auxiliary ions;
an ion analyzer for analyzing analyte ions;
ion transport means for transporting analyte ions into the ion analyser and rejecting auxiliary ions into the ion analyser; an ion transport device is located between the first ion source and the ion analyzer.
According to the embodiment, the space charge effect among the analyte ions can be obviously reduced, the ion cloud broadening of the analyte ions can be reduced, and the analysis performance of an ion analysis instrument (such as a mass spectrometer, an ion mobility spectrometer and the like) can be obviously improved.
Preferably, the charge center of the auxiliary ion is located inside the auxiliary ion structure.
According to the above embodiment, by locating the charge center of the auxiliary ion within the auxiliary ion structure, the auxiliary ion can effectively attract the analyte ions to the surroundings to reduce the space charge effect without neutralizing the analyte ions and without reacting with the analyte ions into other substances.
Preferably, the analyte ions react with the auxiliary ions to neutralize no more than 1%, 5%, 10%, 20%, 30%, 40% or 50% of the total analyte ions.
According to the above embodiment, the number of ions that are neutralized by the reaction between the analyte ions and the auxiliary ions is further limited to the range of the ratio of the total analyte ions, and the range and degree of the chemical reactions that are not likely to occur are specified, so that the effect of the auxiliary ions on the reduction of the space charge effect is significant, but the analyte ions are not neutralized, and no other interference is introduced.
Preferably, the method further comprises the following steps: and at least one vacuum interface is arranged on the vacuum interface and is positioned behind the first ion source and in front of the ion transmission system.
According to the embodiment, the vacuum interface is arranged, so that the ion cloud can enter, and ions can be effectively analyzed.
Preferably, the ion transport device comprises: ion optics driven by a radio frequency voltage that generates an electric field that simultaneously confines both analyte ions and auxiliary ions.
According to the above embodiment, by providing the ion optical device, the electric field generated by the radio frequency voltage can simultaneously confine the analyte ions and the auxiliary ions, thereby effectively guiding the ions, and the broadening of the analyte ions can be suppressed to a certain extent in the presence of the auxiliary ions of opposite polarity, thereby facilitating efficient ion capture, guidance and focusing.
Preferably, a dc voltage is applied to the ion transport means, and the electric field formed by the dc voltage is capable of driving analyte ions into the ion analysis means and rejecting auxiliary ions into the ion analysis means.
According to the above embodiments, analyte ions can be smoothly transferred from the first stage vacuum to the second stage vacuum, but auxiliary ions of opposite polarity are rejected from the second stage vacuum, thereby improving the sensitivity of the analysis.
Preferably, the vacuum interface is a capillary structure, and two ends of the capillary are respectively close to the atmospheric pressure environment and the vacuum.
Preferably, the first and second ion sources are electrospray ionization sources, laser ionization sources, chemical ionization sources, electron bombardment ionization sources, inductively coupled plasma ionization sources, or ion optics modules that can provide ions and are located upstream of the ion analyzer.
Preferably, the first ion source and the second ion source are capable of time-sharing alternating operation and are capable of causing ion clouds of analyte ions and ion clouds of auxiliary ions generated at different times to coincide in spatial distribution at the same time.
According to the above embodiment, the positive ion cloud of the analyte ions and the negative ion cloud of the auxiliary ions are alternately generated, and sampling analysis is performed in the overlapped region, thereby further improving the accuracy of analysis.
Preferably, the ion analyser is a mass analyser.
Preferably, the mass analyser comprises one or more of a quadrupole rod type, an ion trap type, a time-of-flight type, a magnetic mass spectrum type or a fourier transform type.
Preferably, the mass analyser is of the time-of-flight type, the region where the ion cloud of the auxiliary ions and the ion cloud of the analyte ions coincide in spatial distribution being located in front of the repulsion region of the time-of-flight mass spectrum.
According to the above embodiment, the broadening due to the space charge effect of the analyte ion cloud can be reduced due to the presence of the auxiliary ion cloud, thereby further compressing the ion beam and effectively improving the mass spectral resolution.
Preferably, the ion analyser is an ion mobility spectrometry analyser.
Preferably, the method further comprises the following steps: an ion mobility analyzer, the number of which is one, the ion mobility analyzer being located upstream of the ion analyzer, the region of coincidence of the ion cloud of the auxiliary ions and the ion cloud of the analyte ions being located inside the ion mobility analyzer, the ion analyzer being a mass analyzer.
The invention also provides an ion analysis method, which is characterized by comprising the following steps:
providing a first ion source to provide analyte ions;
providing a second ion source to provide auxiliary ions; the auxiliary ions have a polarity opposite to the analyte ions, the ion cloud of the auxiliary ions and the ion cloud of the analyte ions are spatially coincident, and at least a portion of the analyte ions do not chemically react with the auxiliary ions;
providing an ion analyzer for analyzing analyte ions;
providing ion transport means for transporting analyte ions into the ion analyser and rejecting auxiliary ions into the ion analyser; an ion transport device is located between the first ion source and the ion analyzer.
Preferably, the charge center of the auxiliary ion is located inside the auxiliary ion structure.
Preferably, the analyte ions react with the auxiliary ions to neutralize no more than 1%, 5%, 10%, 20%, 30%, 40% or 50% of the total analyte ions.
Preferably, the method further comprises the following steps:
a vacuum interface is provided, the vacuum interface having one located after the first ion source and before the ion transport system.
Preferably, the ion transport device comprises:
ion optics driven by a radio frequency voltage that generates an electric field that simultaneously confines both analyte ions and auxiliary ions.
Preferably, the method further comprises the following steps:
a dc voltage is applied to the ion transport device and an electric field formed by the dc voltage is capable of driving the analyte ions into the ion analysis device and rejecting the auxiliary ions into the ion analysis device.
As described above, the ion analysis apparatus and method of the present invention can significantly reduce the space charge effect between analyte ions, reduce the ion cloud broadening of the analyte ions, and significantly improve the analysis performance of an ion analysis instrument (e.g., a mass spectrometer, an ion mobility spectrometer, etc.) by providing a large number of auxiliary ions having a polarity opposite to that of the analyte ions and not easily reacting with the analyte ions. For example, on one hand, the ion spatial density is improved, so that the ion transmission efficiency, namely the sensitivity, in the mass spectrometer is improved; on the other hand, because the initial ion cloud broadening is reduced, the resolution in the ion mobility spectrometer is improved.
Drawings
Fig. 1 is a schematic structural view of an ion analyzer according to embodiment 1 of the present invention;
fig. 2 is a schematic structural view of an ion analyzer according to embodiment 2 of the present invention;
fig. 3 is a schematic structural view of another ion analysis apparatus according to embodiment 2 of the present invention;
fig. 4 is a schematic structural view of an ion analyzer according to embodiment 3 of the present invention;
FIG. 5 is a schematic diagram of the positive and negative AC high voltage of FIG. 4;
fig. 6 is a schematic structural view of an ion analyzer according to embodiment 4 of the present invention;
fig. 7 is a schematic structural view of an ion analyzer according to embodiment 5 of the present invention;
fig. 8 is a schematic configuration diagram of an ion analyzer according to embodiment 6 of the present invention.
Description of reference numerals:
1-a first ion source; 2-a second ion source; 3-a first ion cloud; 4-a second ion cloud; 3' -first forming an ion cloud; 4' -second forming an ion cloud; 5-a capillary tube; 6-an ion transport device; 7-an ion analyzer; 8-a first ion guide device; 9-a first vacuum interface; 10-a second ion guide device; 11-a second vacuum interface; 12-a first mass analyser; 13-a first detector; 14-a flight chamber; 15-a preceding stage region; 16-an operating device; 17-a repulsion zone; an 18-ion gate; 19-an ion transfer tube; 20-a second detector; 21-a ground electrode; 22-a first electrolance; 23-a first coaxial tube; 24-a second coaxial tube; 25-positive and negative alternating-current high voltage; 26-a second electrojet needle; 27-a first position; 28-a second position; 29-ion clusters; 30-an ion-diverting means; 31-a second mass analyser; 32-third detector.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
It should be understood that the structures, ratios, sizes, etc. shown in the drawings and attached to the description are only for understanding and reading the disclosure of the present invention, and are not intended to limit the practical conditions of the present invention, so that the present invention has no technical significance, and any modifications of the structures, changes of the ratio relationships, or adjustments of the sizes, should still fall within the scope of the technical contents of the present invention without affecting the efficacy and the achievable purpose of the present invention. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.
Example 1
Fig. 1 is a schematic structural diagram of an ion analysis apparatus provided in this embodiment, and as shown in fig. 1, the ion analysis apparatus includes: a first ion source 1 for providing analyte ions; a second ion source 2 for providing auxiliary ions; the positive and negative polarities of the auxiliary ions are opposite to those of the analyte ions, and the ion clouds of the auxiliary ions and the ion clouds of the analyte ions are superposed in spatial distribution; an ion analyser 7 for analysing analyte ions; ion transport means 6 for transporting analyte ions into the ion analyser 7 and rejecting auxiliary ions into the ion analyser 7; an ion transport device 6 is located between the first ion source 1 and the ion analyser 7.
According to the embodiment provided in this example, the first ion source 1 is used to provide analyte ions, and preferably, the first ion source 1 is an electrospray ionization source in an atmospheric environment, the polarity is positive (i.e., a positive high voltage is applied to the electrospray needle), and the spray generates a first ion cloud 3, and the first ion cloud 3 contains not only a large number of positive ions but also a large number of positively charged droplets. The second ion source 2 is used to provide auxiliary ions, preferably an electrospray ionization source, with negative polarity (i.e., a negative high voltage is applied to the electrospray needle), and the second ion cloud 4 is generated after spraying, and the second ion cloud 4 contains not only a large amount of negative ions but also a large amount of negatively charged droplets. The second ion cloud 4 of auxiliary ions is spatially coincident with the first ion cloud 3 of analyte ions, preferably at the distal end of the spray ion cloud, i.e. where charged droplets are sufficiently desolvated, or at the proximal end of the spray ion cloud, i.e. where the ion cloud density is high, depending on the flow rate, temperature, etc. of the first and second ion sources 1, 2.
Since a large number of negative ions (i.e. auxiliary ions) are provided in the first ion cloud 3 of the positive ion cloud of analyte ions, the charge repulsion between the positive ions is largely cancelled and the space charge effect is reduced. Starting from a simple model, with the distribution of spherical ion clouds with radius R, the total charge of positive charges is Q +, the total charge of negative charges is Q-, then the electric field strength of charge repulsion for a certain positive ion on the spherical surface can be calculated by using gaussian theorem as:
it can be seen that the introduction of negative charges reduces the repulsion between positive charges. In an ideal case, the space charge effect can even be completely eliminated if the total amount of positive and negative charges is equal and uniformly distributed. In practice, the type, concentration, etc. of the auxiliary ions may be adjusted to controllably reduce the space charge effects of the analyte ions. In this embodiment, the spatial distribution of the analyte ion cloud first ion cloud 3 is limited, and the spatial density of ions is greatly increased, which is equivalent to the ion cloud being compressed. It should be noted that the spatial density of the negative ion cloud second ion cloud 4 is also higher than in the absence of the ion source 1. The analyte ions in the compressed first ion cloud 3 pass through the ion transport device 6 and enter the ion analyser 7 to be analysed.
The ion transport device 6 comprises a capillary 5 for interface between atmospheric pressure and vacuum, the capillary 5 has one or more parallel, the capillary 5 is located in the first stage vacuum of the first ion guide device 8, located in the second stage vacuum of the second ion guide device 10, and located in the first, second vacuum between the vacuum, and the second vacuum interface between the second, third vacuum 11. Since the space charge effect of the first ion cloud 3 is suppressed and the ion density is increased, the rate of entering the capillary 5 is also significantly increased, thereby improving the sensitivity of the analysis. The first ion guiding means 8 may be an rf driven ion optical device such as an electrode array applying an rf quadrupole field, which is well known in the art, which binds both analyte ions and auxiliary ions of opposite polarity. The ion analyser 7, preferably a mass analyser, comprises a first mass analyser 12, and a first detector 13.
In the above embodiment, the reduction of the space charge effect of the analyte ions occurs not only in the region where the first ion cloud 3 and the second ion cloud 4 coincide, but also in any region where auxiliary ions are present during the subsequent transport of the analyte ions. For example, in the capillary 5, the analyte ion space charge effect is typically very severe if there are no auxiliary ions, which can result in ion losses of up to 90% from wall collisions, but can be significantly reduced in the presence of auxiliary ions. For another example, at the end of the capillary 5, the supersonic gas flow due to vacuum expansion causes the ion beam to widen sharply, and the widening is further aggravated by the presence of space charge effects, which causes difficulties in ion trapping, guiding and focusing using the ion guide 8, but in the case of the presence of auxiliary ions of opposite polarity in this embodiment, widening of analyte ions is suppressed to some extent, which is more advantageous for efficient ion trapping, guiding and focusing.
In the above embodiment, in order to avoid interference with the mass spectrometry analysis by the auxiliary ions entering the first mass analyser 12, a dc voltage difference may be applied across part of the ion transport means, for example a dc potential lower than that of the ion guide means 8, across the first vacuum port 9, to allow analyte ions to pass smoothly from the first stage vacuum to the second stage vacuum, but to reject auxiliary ions of the opposite polarity from entering the second stage vacuum. The dc voltage difference may also be applied to other parts of the ion transport device, or between the ion transport device 6 and the ion analyser 7.
In the above embodiments, the type, concentration, etc. of the auxiliary ions can be selected and optimized manually. For example, in order to achieve significant reduction in the effect of the auxiliary ions on the space charge, but not to neutralize the analyte ions and to introduce other interference, the auxiliary ions are selected to be ions that do not readily react with the analyte ions. The extent and degree of so-called "chemical reaction" is well known in the art and the invention may be further defined as the amount of ions neutralized by the reaction of analyte ions with auxiliary ions being no more than 1%, 5%, 10%, 20%, 30%, 40% or 50%, preferably no more than 10%, of the total analyte ions. The auxiliary ion in the present invention may preferably be an ion having a charge center located inside the ionic structure thereof, i.e., a so-called "cage ion" (caged ion). Therefore, the auxiliary ions can still effectively attract the analyte ions to the periphery of the auxiliary ions to reduce the space charge effect, but the auxiliary ions can not neutralize the analyte ions and can not react with the analyte ions into other substances, and under the blocking action of the direct current voltage difference of the later stage, the auxiliary ions can be smoothly separated from the analyte ions with opposite polarities, so that the mass spectrometry is not influenced.
In the above embodiments, the first ion source 1 and the second ion source 2 may be electrospray ionization sources, or may be other types of ionization sources, such as chemical ionization sources (CI), photo ionization sources (PI), electron impact ionization sources (EI), laser ionization sources (MALDI), inductively coupled plasma ionization sources (ICP), and the like. In addition to ionization sources, ion sources in the broad sense (ion sources), i.e., ion optics that provide ions and are located upstream of the ion analyzer, are also possible. As long as it is ensured that ions of opposite polarity are generated. The analyte ions may be made positive ions, the auxiliary ions negative ions, or vice versa. The ion generating region may be an atmospheric pressure environment or a vacuum environment. The region where the two ions are mixed, i.e., the region where the ion clouds overlap, is not a limitation of the present invention, as long as it is before entering the ion analyzer.
In the above embodiments, the first mass analyzer 12 may be of the quadrupole rod type, the ion trap type, the time-of-flight type, the magnetic mass spectrum type, the fourier transform type, or a combination of the above types.
Example 2
Fig. 2 and fig. 3 are schematic diagrams of two structures of the ion analysis apparatus provided in this embodiment, and the ion analysis apparatus provided in this embodiment is based on the embodiment of embodiment 1, and is not specifically described, but is the same as the embodiment of embodiment 1, and is not described again here.
As shown in fig. 2, the present embodiment provides an ion analysis apparatus, based on the embodiment of example 1, wherein the first ion source 1 and the second ion source 2 are both electrospray ionization sources, and the first ion source 1 and the second ion source 2 are disposed in parallel with each other. A ground electrode 21 is provided between the two ion sources, and stable spraying can be achieved. The ground electrode 21 prevents interference between the positive and negative sprays, and allows the positive and negative ion clouds to approach each other to a greater extent and spatially coincide. The capillary 5 is arranged in this overlapping area and placed perpendicular to the paper. In this embodiment, a certain dc potential may be applied to the ground electrode 21, so that the direction and spread of the electrospray ion cloud can be adjusted as needed.
As shown in fig. 3, in the ion analysis apparatus provided in this embodiment, based on the implementation manner of embodiment 1, the first ion source 1 and the second ion source 2 are coaxially disposed electrospray ionization sources. The first ion source 1, which consists of a first electrical needle 22 applying a positive high voltage and a grounded first coaxial tube 23 into which an atomizing or heating gas can be introduced to help form a spray, or to help desolventize, forms an analyte ion cloud first ion cloud 3; the second ion source 2, which consists of a grounded first coaxial tube 23 and an outer second coaxial tube 24 applying a negative high voltage, forms an auxiliary ion cloud second ion cloud 4 surrounding the outer side of the first ion cloud 3; the two ion clouds form a coaxial coincidence region, which can achieve the purpose of reducing the space charge effect in the first ion cloud 3 of the analyte ion cloud. It should be noted that, in this example, the second ion source 2 may not adopt the electrospray method, but a large amount of negative ions generated by any ionization method may be introduced between the first coaxial tube 23 and the outer second coaxial tube 24 to form the auxiliary ion cloud second ion cloud 4.
Example 3
Fig. 4 is a schematic structural diagram of the ion analysis apparatus provided in this embodiment. The ion analysis apparatus provided in this embodiment is based on the embodiment of embodiment 1, and is not specifically described, but is the same as the embodiment of embodiment 1, and is not repeated herein.
As shown in fig. 4, in this embodiment, the positions of the first ion source 1 and the second ion source 2 for generating ions may be the same, and it should be noted that the first ion source 1 and the second ion source 2 are operated alternately in time division. Still taking the example of an electrospray ionization source, the first ion source 1 enters the flow of analyte from a first location 27, the second ion source 2 enters the flow of auxiliary ions from a second location 28, and both ion sources use the same second electrospray needle 26 to produce electrospray. However, by applying a positive and a negative ac high voltage 25 to the electrospray needle that varies with time as shown in fig. 5, a first ion cloud 3 of positive ions of analyte ions and a second ion cloud 4 of negative ions of auxiliary ions can be alternately generated. The two ion clouds are not overlapped in space position when just generated, but a certain mechanism can be applied, so that the two ion clouds are overlapped in the downward movement transmission process, and sampling is carried out by using a capillary 5 in the overlapped area; preferably, a direct current electric field is applied in the space, so that the positive ion cloud is accelerated and the negative ion cloud is decelerated, and then the generated positive ion cloud can catch up with the negative ion cloud; preferably, negative ions with low mobility are selected as auxiliary ions, so that positive ions can catch up with the negative ions more quickly; preferably, the ion clouds of both polarities are trapped using radio frequency voltages, standing air waves or other forms, causing mixing. In this example, for some analytes that can generate ions of both positive and negative charges under different conditions, the streams at the first location 27 and the second location 28 can be combined into the same path, i.e., the auxiliary ions are of the same type as the analyte ions, but have different positive and negative polarities.
Example 4
Fig. 6 is a schematic structural diagram of an ion analysis apparatus provided in this embodiment, which is based on the embodiment of example 1, and is not specifically described, but is the same as the embodiment of example 1, and thus is not repeated herein.
As shown in fig. 6, this embodiment is selected as an orthogonal time-of-flight mass spectrometer as the mass analyzer. In particular, in this embodiment, electrospray ionization sources of positive and negative polarity can still be used to generate a first ion cloud 3 and a second ion cloud 4 using the first ion source 1 and the second ion source 2; after being transported, the first ion cloud 3 and the second ion cloud 4 form a first formed ion cloud 3 'and a second formed ion cloud 4', respectively, and enter a foreline region 15 (i.e., the foreline region of the repulsion region 17) before the flight chamber 14, where they are mixed. The foreline region 15 typically requires a manipulator 16, and the manipulator 16 may be capable of cooling, compressing, collimating, etc. the first formed ion cloud 3' of the analyte ion cloud to improve the resolution of the time-of-flight mass spectrum. It should be noted that the presence of the auxiliary ion cloud second forming ion cloud 4 'reduces the broadening due to the space charge effect of the analyte ion cloud first forming ion cloud 3', thereby further compressing the ion beam to achieve higher mass spectral resolution. Mixing of the positive and negative ion clouds can also occur within the repulsion region 17 of the time-of-flight mass spectrometry to perform time-of-flight mass spectrometry immediately after compression.
Example 5
Fig. 7 is a schematic structural diagram of an ion analysis apparatus provided in this embodiment, which is based on the embodiment of example 1, and is not specifically described, but is the same as the embodiment of example 1, and thus is not repeated herein.
As shown in fig. 7, in the present embodiment, the ion analyzer 7 is not a mass spectrometer, but an ion mobility spectrometer, which includes an ion gate 18, an ion mobility tube 19 for mobility analysis, and a second detector 20. The ion transport device 6 may be used not only for transport of analyte ions generated by the first ion source 1, but may also assist the charged droplets in desorbing solvent, generating ions. Second ion cloud 4 of auxiliary ions generated by second ion source 2 may be mixed with first ion cloud 3 of the analyte ion cloud before ion gate 18 to reduce the spatial distribution of the analyte ion cloud and produce a finer ion beam to improve the throughput and sensitivity of the analyzer. This mixing may also occur after ion gate 18 and before mobility analysis to reduce initial beam broadening and to improve mobility spectrum resolution. If the ion gate is a multi-layered electrode structure, such mixing can occur within the ion gate, which can also improve the resolution of the mobility spectrum.
Example 6
Fig. 8 is a schematic structural diagram of an ion analysis apparatus provided in this embodiment, which is based on the embodiment of example 1, and is not specifically described, but is the same as the embodiment of example 1, and thus is not repeated herein.
As shown in fig. 8, the ion analyzer provided in this embodiment is a mobility spectrometry-mass spectrometry analyzer, ions generated by the first ion source 1 of the analyte ion source pass through the ion transport device 6 and the ion gate 18, and enter the ion mobility tube 19 for mobility analysis, and in the ion mobility tube, ions with different mobilities are separated to form different ion clouds or ion clusters 29. The ions separated by the mobility spectrometry pass through an ion diversion arrangement 30 and enter the ion analyser 7 for mass analysis, where the ion analyser 7 may comprise a second mass analyser 31 and a third detector 32. The mobility spectrum resolution of the ion mobility tube 19 is inversely related to the space charge effect of the ion cluster 29, for example, if the space charge effect is strong in the case of a large analyte ion concentration, the mobility spectrum peak is significantly widened and the resolution is reduced. At this time, when auxiliary ions of opposite polarities are introduced by the second ion source 2 and the ion cloud 4 of the auxiliary ions spatially overlaps the ion cluster 29, the spatial spread of the ion cluster 29 can be reduced and the mobility spectrum resolution can be improved. The ion mobility tube 19 in this embodiment may be replaced by another type of mobility spectrometer, for example, a traveling wave (traveling wave) mobility analyzer, a trapped ion mobility analyzer (TIMS), a differential ion mobility spectrometer (DMA), a high field asymmetric waveform ion mobility spectrometer (FAIMS), or the like. In particular, for a mobility analyzer of the TIMS type, the apparatus and method of the present invention can not only improve the resolution of the mobility analysis, but also avoid saturation of the ion trapping capacity, thereby improving the dynamic range.
The invention also provides an ion analysis method, which comprises the following steps: providing a first ion source to provide analyte ions; providing a second ion source to provide auxiliary ions; the positive and negative polarity of the auxiliary ion is opposite to that of the analyte ion, and the ion cloud of the auxiliary ion and the ion cloud of the analyte ion are coincident in spatial distribution; providing an ion analyzer for analyzing the analyte ions; providing ion transport means for transporting said analyte ions into said ion analyzer and rejecting said auxiliary ions into said ion analyzer; the ion transport device is located between the first ion source and the ion analyzer.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (20)
1. An ion analysis apparatus, comprising:
a first ion source for providing analyte ions;
a second ion source for providing auxiliary ions;
the auxiliary ion is of opposite positive or negative polarity to the analyte ion; the ion cloud of the auxiliary ions and the ion cloud of the analyte ions are spatially coincident, and at least a portion of the analyte ions do not chemically react with the auxiliary ions;
an ion analyzer for analyzing the analyte ions;
ion transport means for transporting said analyte ions into said ion analyser and rejecting said auxiliary ions into said ion analyser, said ion transport means being located between said first ion source and said ion analyser.
2. The ion analysis apparatus of claim 1, wherein:
the charge center of the auxiliary ion is located inside the auxiliary ion structure.
3. The ion analysis apparatus of claim 1, wherein:
the analyte ions react with the auxiliary ions to neutralize the analyte ions in an amount not exceeding any one of 1%, 5%, 10%, 20%, 30%, 40% or 50% of the total amount of the analyte ions.
4. The ion analysis apparatus of claim 1, further comprising:
the vacuum interface is provided with at least one, and the vacuum interface is positioned behind the first ion source and in front of the ion transmission device.
5. The ion analysis apparatus of claim 1, wherein the ion transport apparatus comprises:
ion optics driven by a radio frequency voltage that generates an electric field capable of simultaneously binding the analyte ions and the auxiliary ions.
6. The ion analysis apparatus of claim 1, wherein:
a dc voltage is applied to the ion transport device, and an electric field formed by the dc voltage is capable of driving the analyte ions into the ion analyzer and rejecting the auxiliary ions into the ion analyzer.
7. The ion analysis apparatus according to claim 4, wherein:
the vacuum interface is a capillary tube, and the two ends of the capillary tube are respectively in an environment close to atmospheric pressure and a vacuum environment.
8. The ion analysis apparatus of claim 1, wherein:
the first ion source or the second ion source is one of an electrospray ionization source, a laser ionization source, a chemical ionization source, an electron bombardment ionization source, an inductively coupled plasma ionization source, or an ion optical device that can provide ions and is located upstream of the ion analyzer.
9. The ion analysis apparatus of claim 1, wherein:
the first ion source and the second ion source operate alternately in time division and are capable of overlapping ion clouds of the analyte ions and the auxiliary ions generated at different times in the spatial distribution at the same time.
10. The ion analysis apparatus according to claim 1, wherein:
the ion analyser is a mass analyser.
11. The ion analysis apparatus of claim 10, wherein:
the mass analyser is one or more of quadrupole rod type, ion trap type, time of flight type, magnetic mass spectrum type or fourier transform type.
12. The ion analysis apparatus of claim 11, wherein:
the mass analyser is of the time-of-flight type, and the region where the ion cloud of the auxiliary ions and the ion cloud of the analyte ions coincide in spatial distribution is located in a preceding stage of a repulsion region of the time-of-flight type mass analyser.
13. The ion analysis apparatus of claim 1, wherein:
the ion analyzer is an ion mobility spectrometry analyzer.
14. The ion analysis apparatus of claim 1, further comprising:
an ion mobility analyzer upstream of the ion analyzer, a region of coincidence of the ion cloud of the auxiliary ions with the ion cloud of the analyte ions being located inside the ion mobility analyzer, the ion analyzer being a mass analyzer.
15. A method of ion analysis, characterized by: comprises that
Providing a first ion source to provide analyte ions;
providing a second ion source to provide auxiliary ions of opposite polarity to the analyte ions, the ion cloud of the auxiliary ions being spatially coincident with the ion cloud of the analyte ions and at least some of the analyte ions being chemically non-reactive with the auxiliary ions;
providing an ion analyzer for analyzing the analyte ions;
ion transport means is provided between the first ion source and the ion analyser for transporting the analyte ions into the ion analyser and rejecting the auxiliary ions into the ion analyser.
16. The ion analysis method of claim 15, wherein:
the charge center of the auxiliary ion is located inside the auxiliary ion structure.
17. The ion analysis method of claim 15, wherein:
the analyte ions react with the auxiliary ions to neutralize ions in an amount that does not exceed any of 1%, 5%, 10%, 20%, 30%, 40% or 50% of the total analyte ions.
18. The ion analysis method of claim 15, further comprising the steps of:
a vacuum interface is provided after the first ion source and before the ion transport system.
19. The ion analysis method of claim 15, wherein:
the ion transport device includes ion optics driven by a radio frequency voltage that creates an electric field that simultaneously confines the analyte ions and the auxiliary ions.
20. The ion analysis method of claim 15, further comprising the steps of:
applying a dc voltage across said ion transport device, said dc voltage forming an electric field capable of driving said analyte ions into said ion analyser and rejecting said auxiliary ions into said ion analyser.
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