CN113466318A - Control method, system and equipment of super-resolution ion mobility spectrometer - Google Patents
Control method, system and equipment of super-resolution ion mobility spectrometer Download PDFInfo
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Abstract
The invention belongs to the technical field of analytical chemistry and analytical instruments, and discloses a control method, a system and equipment of a super-resolution ion mobility spectrometer, wherein the control method of the super-resolution ion mobility spectrometer comprises the following steps: the ion gate is normally closed and is opened temporarily to obtain an ion spectrogram with a spectral peak higher than a base line; the ion gate is normally opened and is closed temporarily to obtain an ion spectrogram with a spectral peak lower than a baseline; and (4) performing difference between the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram. The invention provides a control method of a super-resolution ion mobility spectrometer by changing a sample introduction mode and data processing by using a super-resolution implementation method in optical imaging, which can reduce or even eliminate the influence of a diffusion phenomenon and coulomb repulsion among ions on the resolution of the ion mobility spectrometer instrument and break through the resolution limit of the ion mobility spectrometer when the distance of a migration tube is fixed.
Description
Technical Field
The invention belongs to the technical field of analytical chemistry and analytical instruments, and particularly relates to a control method, a system and equipment of a super-resolution ion mobility spectrometer.
Background
At present, ion mobility spectrometry is an analytical instrument for separating different sample components by using ion mobility, has the technical advantages of low cost, miniaturization, high detection speed, high sensitivity and the like compared with the traditional mass spectrometry and other large-scale analytical instruments, and is widely applied to various fields of security inspection, analysis, medical treatment and the like.
The detection process of the ion mobility spectrometry can be divided into three stages of ionization, migration and detection, wherein the migration stage is a main stage for separating ions with different components and is completed by an ion gate and a migration tube. When the migration phase begins, the ion gate puts a section of ion sheet into the starting end of the migration tube; then under the action of an electric field force in the migration tube, the ion sheets move along the migration tube, and because the migration rates of different ions in the migration tube are different, the time when the sheets of different ions reach the tail end of the migration tube is different; the detector at the end can convert the arriving ions into a current spectrogram in sequence, and each ion sheet is presented on the current spectrogram in the form of a spectral peak. Through the appearance time of the spectrum peak, the mobility of the corresponding ions in the migration tube can be calculated, and therefore the resolution of the sample species is achieved.
The resolution is an index for evaluating the resolving power of the ion mobility spectrometer on different samples and is defined as the migration time t when the ion mobility spectrometer reaches a Faraday discDSum spectrum half-peak width w0.5The ratio of (a) is developed according to the corresponding influence factors to obtain the formula:
migration time tDThe length of a migration tube is L, the ionic mobility is K, and the voltage on the migration tube is UDDetermining, wherein E is the electric field intensity of the transition region, and E is UD/L。w0.5The time scale width of the ion cluster when the ion cluster arrives at the Faraday disk is composed of two parts, wherein one part is the initial ion cluster time width winjThe other part is the transition time tDBroadening of ion clusters by medium diffusion, where kBBoltzmann constant, e is the unit charge amount. In order to maintain the weak electric field condition, E is usually set to 50V/mm or 100V/mm. Keeping the other parameters unchanged, increasing L is beneficial to improving the resolution, but after E is determined, increasing L means that a direct current power supply with larger output is needed to provide UD. To achieve higher resolution, the method generally adopted is to reduce winj。
The detection limit is an index for determining the response capability of the instrument to the object to be detected, and is defined as the ratio of the corresponding signal peak intensity to the noise intensity. Noise is external interference of a system in the measuring and transmitting processes, the numerical value of the noise is relatively fixed and is generally in the range of 1pA to 10pA, the sensitivity is the ratio of the corresponding signal peak intensity to the sample concentration, the ionization efficiency of the sample is determined by an ionization source and is difficult to change, and therefore the detection limit and the sensitivity are both determined by the final signal peak intensity. Ideally, the ion cluster is a cylinder with flat front and back edges, and the expression of the signal peak value is as follows:
where ρ isvIs the spatial ion density. Under the condition that the shapes of the front edge and the rear edge of the ion cluster are not changed, the door opening time w is increasedinjLonger ion current can enter a migration zone to offset diffusion influence, ion clusters can reach a Faraday disc in a state closer to the initial ion density, and the signal intensity I is improved. But increasing winjThe time resolution R may decrease. Resolution and sensitivity can be considered as both integral and not discussed separately. Resolution and signal strength, among other factors, because of UDThe isoparametric adjustable range is limited, and the spatial ion density rho must be increased when the sensitivity is required to be increased under the condition of not reducing the resolution of the instrumentvSimilarly at increasing ρvThen can shorten winjThereby achieving higher resolution when the signal strengths are the same.
It can be seen from the above formula that the resolution is equal to the ratio of the peak migration time to the half-peak width, and the longer the migration time, the narrower the half-peak width, the higher the resolution. The migration time is the time length required for the ion sheet to reach the tail end of the migration tube from the initial end of the migration tube and is mainly determined by the migration distance; the half-peak width is the width of the current spectrum peak formed by the ion sheet and is mainly determined by the thickness of the ion sheet along the migration direction. It follows that mobility enhancement is mainly achieved by two improvements, namely, increasing ion transit time, or reducing the thickness of the ion sheet.
Increasing the migration distance is an effective method for increasing the migration time, but there is a limit to the resolution improvement effect because the diffusion phenomenon and coulomb repulsion between ions cause the thickness of the ion sheet to increase as the migration time increases, thereby offsetting the increase of the migration time to the resolution. Even if the migration distance is increased further on the basis of the resolution limit, the resolution of the instrument cannot be further improved. Therefore, a new super-resolution ion mobility spectrometer and a control method thereof are needed.
Through the above analysis, the problems and defects of the prior art are as follows:
the low resolution of ion mobility spectrometers and the consequent low selectivity and high false alarm rates. The problem of how to improve the separation capacity while maintaining its low detection limit and high sensitivity has been of great interest to IMS researchers.
The difficulty in solving the above problems and defects is: from the calculation formula of the resolution, it can be seen that it is desirable to increase the resolution without affecting the detection limit, either by increasing the migration time or by decreasing the half-peak width:
(1) by reducing the half-peak width, the resolution improvement effect inevitably affects the detection limit. Since decreasing the half-peak width means that the total number of ions entering the migration tube at a time is decreased, and the diffusion phenomenon and the existence of coulomb repulsion between ions cause the ion density in the space to have an upper limit, that is, the maximum value of the peak height of the ion mobility spectrum generated at a time is decreased with the decrease of the total number of ions, affecting the detection limit.
(2) By increasing the increase of the migration time, there is a limit to the improvement effect of the resolution, since the increase of the resolution due to the increase of the migration time is offset by the increase of the thickness of the ion sheet caused by the diffusion phenomenon and the coulomb repulsion between the ions. The resolution of the instrument cannot be further improved even if the migration time is increased on the basis of the resolution limit in the prior art.
The significance of solving the problems and the defects is as follows: in the classical method of breaking through the optical diffraction limit of optical super-resolution imaging, stimulated emission depletion fluorescence microscopy, two beams of illumination light are used, one beam is exciting light, and the other beam is depletion light. When the fluorescence molecules in the range of the diffraction spot of the fluorescence molecule are excited by the irradiation of the exciting light, after electrons in the fluorescence molecule are transited to an excited state, the lost light enables part of the electrons at the periphery of the excitation spot to return to a ground state in a stimulated emission mode, and the rest of the excited electrons at the center of the excitation spot are not affected by the lost light and continue to return to the ground state in an autofluorescence mode. Because the wavelength and the propagation direction of the fluorescence and the autofluorescence emitted in the stimulated emission process are different, the photons really received by the detector are all generated by the fluorescence sample positioned in the central part of the excitation light spot in an autofluorescence mode. Thereby, the light emitting area of the effective fluorescence is reduced, thereby improving the resolution of the system.
By adopting the concept, the traditional pulse forward sample injection method (door opening sample injection) can be adopted to create an ion spectrogram with a spectral peak higher than a base line, and the ion spectrogram simulates exciting light; creating an ion spectrogram with a spectral peak lower than a baseline by a traditional pulse negative-direction sample injection method (closed-gate sample injection) to simulate the loss light; and then obtaining an ion spectrogram with reduced effective ion spectrogram width by subtracting the two spectrograms so as to improve the resolution of the instrument under the condition of not influencing the detection limit.
In conclusion, solving the influence of diffusion phenomenon and coulomb repulsion among ions on space ion clusters is the key to improve the resolution while keeping low detection limit and high sensitivity. The influence of diffusion phenomenon and coulomb repulsion among ions on the distribution of the space ion clusters is eliminated, so that the limit of the resolution of the ion mobility spectrometer can be improved, and the application range and the application scene of the ion mobility spectrometer are further expanded. And a more effective technical guarantee is provided for on-site quick detection.
Disclosure of Invention
The invention provides a control method, a system and equipment of a super-resolution ion mobility spectrometer, and particularly relates to a control method, a system and equipment of a super-resolution ion mobility spectrometer by changing a sample introduction mode and processing data.
The invention is realized in such a way that the control method of the super-resolution ion mobility spectrometer comprises the following steps:
step one, normally closing an ion gate and opening the ion gate for a short time to obtain an ion spectrogram with a spectral peak higher than a base line; to obtain temporally separated ion spectra in a short time; the negative effects of the method are that the sample introduction time is short, the utilization rate of ions is low, and the ions can dispersedly move to the periphery of an ion cluster in the sample introduction process.
Step two, the ion gate is normally opened and is closed temporarily, and an ion spectrogram with a spectral peak lower than a baseline is obtained; the generated ion blank interval has no ions, so the generated ion blank area cannot expand to the periphery of the blank area in the sample injection process, and the width of an ion spectrogram with a spectral peak lower than a baseline cannot be increased;
and step three, performing difference on the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram. The method can eliminate the influence of diffusion phenomenon and coulomb repulsion among ions on the width of the spectral peak under the condition of not influencing the height of the spectral peak, and improve the resolution of the ion mobility spectrometer under the condition of not influencing the detection limit.
Further, in step one, the ion gate is a functional unit of the ion mobility spectrometer for controlling the ions to enter the mobility tube, and the ion gate includes a conventional BN type ion gate, a TP type ion gate and a high field ion gate, which are devices capable of allowing or preventing the ions from entering the mobility tube at a certain time.
Furthermore, the migration tube is a linear electric field migration tube, namely, the whole migration tube presents a tubular cavity, two ends of the migration tube are respectively a starting end and a tail end, and an electric field for driving ions to move from the starting end to the tail end exists in the migration tube; wherein the tubular cross-sectional area of the tubular cavity is of any shape.
Further, in the step one, the opening of the ion gate means that ions can enter the migration tube by controlling the ion gate; the detection baseline is the average value of the current generated by the detector when no ion touches the detector; the short duration is less than the time required for the ions to pass through the transfer tube.
Furthermore, in the second step, the closing of the ion gate means that ions cannot enter the migration tube by controlling the ion gate; the detection base line is the average value of current generated after ions continuously arrive at the detector from the starting end under the door opening state; the short duration is less than the time required for the ions to pass through the transfer tube.
Further, the control method of the super-resolution ion mobility spectrometer further comprises an improved ion negative pulse sampling mode, wherein the improved ion negative pulse sampling mode comprises the following steps:
the ion gate is in an open state for a long time, is immediately returned to the open state after being closed for a short time only during sample introduction, and is continuously kept in the open state until the detection is finished;
when the ion gate is opened, the ion current generated by sample ionization can continuously enter the migration tube and is converted into a stable ion current baseline by the detector at the tail end of the migration tube; during the closing time of the ion gate, a small section of blank space without ions is generated at the starting end of the migration tube, the ion blank space divides the stable ion flow in the migration tube into a front part and a rear part, and the front part and the rear part of the ion flow move towards the tail end of the migration tube under the action of an electric field in the migration tube;
because the moving speeds of different types of ions in the migration tube are different, ion blank areas of different ion flows can reach a detector at the tail end of the migration tube at different moments, and an ion spectrogram with an ion current absolute value lower than a detection baseline is formed.
Further, the control method of the super-resolution ion mobility spectrometer further comprises a sub positive and negative pulse cancellation operation, wherein the sub positive and negative pulse cancellation operation comprises:
due to the diffusion phenomenon and the existence of coulomb repulsion among ions, the ions in the ion sheet in the step one move to two sides of the sheet in the migration process, so that the thickness of the ion sheet is increased, and the detection result shows that the width of a spectrum peak is increased and the resolution is reduced; ions before and after the ion blank area in the step two move towards the ion blank area to influence the ion purity of the blank area, and the detection result shows that the height of a spectrum peak is reduced and the signal intensity is reduced;
subtracting the ion positive pulse spectrogram formed in the first step from the ion negative pulse spectrogram formed in the second step, and offsetting the influence of the diffusion phenomenon and the coulomb repulsion; for the ion sheet in the positive pulse sampling mode, the subtracted part is just the ions of the part of the ion cluster which diffuses outwards in the migration process, namely the subtracted part is the part of the ions of which the thickness of the ion sheet is widened due to the diffusion phenomenon and the coulomb repulsion, and the ion concentration of the central part of the ion sheet is not influenced, so that the resolution of the detection result is increased under the condition of not influencing the signal intensity.
Another object of the present invention is to provide a control system of a super-resolution ion mobility spectrometer, which applies the control method of the super-resolution ion mobility spectrometer, the control system of the super-resolution ion mobility spectrometer including:
the first ion spectrogram acquisition module is used for normally closing and momentarily opening the ion gate to obtain an ion spectrogram with a spectral peak higher than a base line;
the second ion spectrogram acquisition module is used for normally opening and temporarily closing the ion gate to obtain an ion spectrogram with a spectral peak lower than a baseline;
and the super-resolution ion spectrogram acquisition module is used for subtracting the ion spectrogram with the spectral peak higher than the baseline from the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
It is a further object of the invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of:
(1) the ion gate is normally closed and is opened temporarily to obtain an ion spectrogram with a spectral peak higher than a base line;
(2) the ion gate is normally opened and is closed temporarily to obtain an ion spectrogram with a spectral peak lower than a baseline;
(3) and (4) performing difference between the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
Another object of the present invention is to provide an information data processing terminal for implementing the control system of the super-resolution ion mobility spectrometer.
By combining all the technical schemes, the invention has the advantages and positive effects that: the invention provides a super-resolution ion mobility spectrometer implementation method by changing a sample introduction mode and data processing by using a super-resolution implementation method in optical imaging, which can reduce or even eliminate the influence of a diffusion phenomenon and coulomb repulsion among ions on the resolution of an ion mobility spectrometer instrument and break through the resolution limit of the ion mobility spectrometer when the distance of a migration tube is fixed.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a control method of a super-resolution ion mobility spectrometer according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a control method of a super-resolution ion mobility spectrometer according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of an ion mobility spectrometry system built by simulation software according to an embodiment of the present invention.
Fig. 4 is a schematic diagram illustrating a control timing of a passing ion gate according to an embodiment of the present invention.
FIG. 5 is a schematic diagram of the distribution state of the space ions after 2.5[ ms ], 5.1[ ms ] and 7.5[ ms ] according to the embodiment of the present invention.
Fig. 6 is a schematic diagram of an ion sheet passing through a space and converted into a corresponding ion spectrum by a detector according to an embodiment of the present invention.
Fig. 7 is a schematic diagram of a control timing sequence through an ion gate according to an embodiment of the present invention.
FIG. 8 is a schematic diagram of the distribution state of the space ions at 2.5[ ms ], 5.1[ ms ], and 7.5[ ms ] according to the embodiment of the present invention.
Fig. 9 is a schematic diagram of an ion sheet passing through a space and converted into a corresponding ion spectrum by a detector according to an embodiment of the present invention.
Fig. 10 is an ion spectrum with a peak above the baseline and an ion spectrum with a peak below the baseline, respectively, obtained in accordance with an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In view of the problems in the prior art, the present invention provides a method, a system and a device for controlling a super-resolution ion mobility spectrometer, which are described in detail below with reference to the accompanying drawings.
As shown in fig. 1, a control method of a super-resolution ion mobility spectrometer provided by an embodiment of the present invention includes the following steps:
s101, normally closing an ion gate and opening the ion gate for a short time to obtain an ion spectrogram with a spectral peak higher than a base line;
s102, normally opening and closing an ion gate for a short time to obtain an ion spectrogram with a spectral peak lower than a baseline;
and S103, performing subtraction on the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
A schematic diagram of a control method of a super-resolution ion mobility spectrometer provided by the embodiment of the invention is shown in fig. 2.
The technical solution of the present invention is further described below with reference to specific examples.
The invention provides a super-resolution ion mobility spectrometer implementation method by changing a sample injection mode and data processing by using a super-resolution implementation method in optical imaging, namely stimulated emission depletion fluorescence microscopy, and aims to reduce or even eliminate the influence of diffusion phenomenon and coulomb repulsion among ions on the resolution of an ion mobility spectrometer instrument and break through the resolution limit of the ion mobility spectrometer when the distance of a migration tube is fixed. The invention can be realized by the following 3 steps:
(1) the ion gate is normally closed and is opened temporarily to obtain an ion spectrogram with a spectral peak higher than a base line;
(2) the ion gate is normally opened and is closed temporarily to obtain an ion spectrogram with a spectral peak lower than a baseline;
(3) and (4) performing difference between the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
The method comprises the following steps: traditional positive pulse of ion advances kind mode specifically includes:
the ion gate is in a closed state for a long time, is opened for a short time only during sample introduction, then immediately returns to the closed state and continuously keeps the closed state until the detection is finished, and a small section of ion sheet of a sample to be detected is placed at the starting end of the migration tube during the opening time of the ion gate.
Then, the ion sheet moves to the end of the migration tube under the action of the electric field in the migration tube. Because the movement speeds of different types of ions in the sample ion sheet are different, the ion sheets of different ions can reach the detector at the tail end of the migration tube at different moments, and an ion spectrogram with an ion current absolute value higher than a detection baseline is formed.
Step two: improved ion negative pulse sampling mode specifically includes:
the ion gate is in an open state for a long time, and is immediately returned to the open state after being closed for a short time only during sample injection and is continuously kept in the open state until the detection is finished. When the ion gate is opened, the ion current generated by sample ionization continuously enters the migration tube and is converted into a stable ion current baseline by the detector at the tail end of the migration tube. During the closing time of the ion gate, a small blank area without ions is generated at the initial end of the migration tube, the ion blank area divides the stable ion flow in the migration tube into a front part and a rear part, and the front part and the rear part of the ion flow move towards the tail end of the migration tube under the action of an electric field in the migration tube. Because the different ion motion speeds in the migration tube are different, ion blank areas of different ion flows can reach a detector at the tail end of the migration tube at different moments, and an ion spectrogram with an ion current absolute value lower than a detection baseline is formed.
Step three: the ion positive and negative pulse cancellation operation specifically comprises the following steps:
due to the diffusion phenomenon and the existence of coulomb repulsion among ions, the ions in the ion sheet in the step one move to two sides of the sheet in the migration process, so that the thickness of the ion sheet is increased, and the detection result shows that the width of a spectrum peak is increased and the resolution is reduced; and (5) the ions before and after the ion blank area in the step (II) move towards the ion blank area, the ion purity of the blank area is influenced, and the detection result shows that the height of a spectrum peak is reduced and the signal intensity is reduced. The method provides that the ion positive pulse spectrogram formed in the first step is subtracted from the ion negative pulse spectrogram formed in the second step, so that the influence of diffusion phenomenon and coulomb repulsion is eliminated, and the resolution of the detection result is improved. Because the subtracted part is just the ions of the part of the ion cluster diffusing outwards in the migration process for the ion sheet in the positive pulse sampling mode, namely the subtracted part is the ions of the part of the ion sheet with widened thickness caused by the diffusion phenomenon and the coulomb repulsion force, and the ion concentration of the central part of the ion sheet is not influenced, thereby increasing the resolution ratio of the detection result without influencing the signal intensity.
In the above steps, the ion gate is a functional unit in the ion mobility spectrometer that controls ions to enter the mobility tube, and the ion gate described in this patent includes conventional BN type ion gate, TP type ion gate, high field ion gate, and other devices that can allow or prevent ions from entering the mobility tube at a certain time.
In the above steps, the migration tube refers to a linear electric field migration tube, that is, the entire migration tube presents a tubular cavity, two ends of the migration tube are respectively a start end and a tail end, and an electric field for driving ions to move from the start end to the tail end exists in the migration tube.
Wherein the tubular cross-sectional area of the tubular cavity can be any shape.
In the above step, the opening of the ion gate means that ions can enter the transfer tube by controlling the ion gate.
In the above steps, the closing of the ion gate means that ions cannot enter the migration tube by controlling the ion gate.
In the above steps, the duration of the short-term is less than the time required for the ions to pass through the migration tube.
In the first step, the one-time detection process is from the beginning of the ion entering the migration tube to the end of the ion receiving by the detector.
The detection end means that the detection is finished after all ion sheet groups in the migration tube space are converted into current intensities corresponding to different moments by the detector.
In the second step, the primary detection process means that the ions from the ion blank area entering the migration tube to the ion blank area are received by the detector and then are finished.
Wherein, the detection end means that all ion blank areas in the migration tube space are converted into low-current ion blank area spectrograms corresponding to different moments by the detector, namely the detection end is obtained.
In the first step, the detection baseline is an average value of current generated by the detector when no ion touches the detector.
In the second step, the detection baseline is the average value of current generated after ions reach the detector from the starting end continuously under the door opening state.
In the third step, the subtraction of the ion positive pulse spectrogram formed in the first step and the ion negative pulse spectrogram formed in the second step refers to subtraction after various types of operations, and the higher resolution than that obtained by singly using a positive pulse mode or a negative pulse mode is obtained by subtracting a diffusion part, so that the protection range is regarded as the protection range of the invention.
The technical effects of the present invention will be described in detail with reference to simulation experiments.
As shown in fig. 3, a general ion mobility spectrometry system is built through simulation software, the whole figure shows a migration tube, wherein a uniform electric field for driving ions to move from left to right exists, ions are continuously generated in an ion generation area, and an ion gate separates the ion generation area from the ion migration area.
In the simulation, the electric field intensity in the ion mobility region was set to 50[ V/mm ]]The total length is 90[ mm ]]The approximate mobility of the ion is 0.59[ cm ]2/V·s]At a temperature of 293.15[ K ]]The number of ionic charges is set to 2, and the entire environment is air.
After the first step, the control sequence of the ion gate is as shown in fig. 4, the ion gate is in a closed state for a long time, and is opened at 5[ ms ], and is closed again at 5.1[ ms ], and the opening time is 100[ mu ] s ].
Then at 2.5[ ms ], 5.1[ ms ], 7.5[ ms ], the distribution of the spatial ions is as shown in fig. 5. At 2.5[ ms ], no ions enter the mobility zone; at time 5.1[ ms ], the ion gate is opened for 0.1[ ms ] to insert ions of corresponding width, such as the ion sheet in the red portion of FIG. 5 (b); at the 7.5[ ms ], the ion sheet moves for 2.5[ ms ], the ion sheet moves along the migration tube to the tail end of the migration tube at the position, and the space width of the ion sheet is widened due to the diffusion phenomenon and the coulomb repulsion force at the thickness.
Finally, the ion sheet in the space is converted into a corresponding ion spectrogram by a detector, as shown in fig. 6, the ion baseline is 0, the spectral peak is higher than the ion baseline, the migration time of the simulated spectrogram obtained through calculation is 22.4[ ms ], the half-peak width is 0.82[ ms ], and the obtained resolution is 27.4[ dimensionless ].
After the second step, the control sequence of the ion gate is as shown in fig. 7, the ion gate is in an open state for a long time, the ion gate is closed at 5[ ms ], and is opened again at 5.1[ ms ], and the opening time is 100[ mus ].
Then at 2.5[ ms ], 5.1[ ms ], 7.5[ ms ], the distribution of the space ions is as shown in fig. 8. At 2.5[ ms ], ions enter the migration zone uniformly; at 5.1[ ms ], the ion gate is closed for 0.1[ ms ], and an ion blank region with a corresponding width is generated, as shown in fig. 8(b), the red part is an ion region, and the region between the two red parts is an ion blank region; at the 7.5[ ms ], the ion blank area moves for 2.5[ ms ], the ions of the front part and the ions of the rear part move to the tail end of the migration tube along the migration tube at the positions, and the width of the ion blank area is narrowed in the thickness of the ion blank area due to the diffusion phenomenon and the coulomb repulsion of the ions at the front part and the rear part of the ion blank area.
Finally, the ion blank detector in the space is converted into a corresponding ion spectrogram as shown in fig. 9, the ion baseline is 1, the spectral peak is lower than the ion baseline, the migration time of the simulated spectrogram obtained through calculation is 22.4[ ms ], the half-peak width is 0.82[ ms ], and the obtained resolution is 27.4[ dimensionless ].
As shown in fig. 10, through the first step and the second step, the present invention obtains an ion spectrum with a peak higher than the baseline and an ion spectrum with a peak lower than the baseline, respectively, and for the ion spectrum with a peak higher than the baseline, the widths of the left and right sides of the peak of the ion spectrum are caused by diffusion phenomenon and coulomb repulsion in the ion sheet, so as to widen the half-peak width of the spectra; for the ion spectrogram with the peak lower than the baseline, the height change of the left side and the right side of the ion spectrogram is caused by the diffusion phenomenon and coulomb repulsion in the ions before and after the ion blank area, and the height of the spectrogram peak is reduced. Through the third step, only the spectrum part above the baseline generated in the first step is taken as the final target spectrum after the second spectrum is subtracted from the first spectrum in the first step. It can be seen that the migration time of the obtained result was not changed and was still 22.4[ ms ], the half-width of the half-peak was changed to 0.41[ ms ], and the resolution was 54.8[ dimensionless ]. The temperature is doubled.
In the practical use process, all methods for canceling the influence caused by the ion diffusion phenomenon and the coulomb repulsion between ions through a series of methods such as the difference or weighting between an ion spectrogram with a spectral peak higher than a base line and an ion spectrogram with a spectral peak lower than the base line belong to the protection content of the scheme.
In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When used in whole or in part, can be implemented in a computer program product that includes one or more computer instructions. When loaded or executed on a computer, cause the flow or functions according to embodiments of the invention to occur, in whole or in part.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A control method of a super-resolution ion mobility spectrometer is characterized by comprising the following steps:
the ion gate is normally closed and is opened temporarily to obtain an ion spectrogram with a spectral peak higher than a base line;
the ion gate is normally opened and is closed temporarily to obtain an ion spectrogram with a spectral peak lower than a baseline;
and (4) performing difference between the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
2. The method for controlling a super resolution ion mobility spectrometer of claim 1, wherein the ion gate is a functional unit of the ion mobility spectrometer that controls the entrance of ions into the mobility tube, and the ion gate includes devices that can allow or prevent ions from entering the mobility tube at a certain time, such as a conventional BN type ion gate, a TP type ion gate, and a high field ion gate.
3. The control method of the super-resolution ion mobility spectrometer of claim 2, wherein the migration tube is a linear electric field migration tube, i.e. the entire migration tube presents a tubular cavity, two ends of the migration tube are respectively a starting end and a tail end, and an electric field for driving ions to move from the starting end to the tail end exists in the migration tube; wherein the tubular cross-sectional area of the tubular cavity is of any shape.
4. The control method of the super resolution ion mobility spectrometer of claim 1, wherein the opening of the ion gate means that ions can enter the mobility tube by controlling the ion gate; the detection baseline is the average value of the current generated by the detector when no ion touches the detector; the short duration is less than the time required for the ions to pass through the transfer tube.
5. The method for controlling a super-resolution ion mobility spectrometer according to claim 1, wherein the closing of the ion gate means that ions cannot enter the mobility tube by controlling the ion gate; the detection base line is the average value of current generated after ions continuously arrive at the detector from the starting end under the door opening state; the short duration is less than the time required for the ions to pass through the transfer tube.
6. The method for controlling a super resolution ion mobility spectrometer according to claim 1, further comprising an improved ion negative pulse sampling mode, wherein the improved ion negative pulse sampling mode comprises:
the ion gate is in an open state for a long time, is immediately returned to the open state after being closed for a short time only during sample introduction, and is continuously kept in the open state until the detection is finished;
when the ion gate is opened, the ion current generated by sample ionization can continuously enter the migration tube and is converted into a stable ion current baseline by the detector at the tail end of the migration tube; during the closing time of the ion gate, a small section of blank space without ions is generated at the starting end of the migration tube, the ion blank space divides the stable ion flow in the migration tube into a front part and a rear part, and the front part and the rear part of the ion flow move towards the tail end of the migration tube under the action of an electric field in the migration tube;
because the moving speeds of different types of ions in the migration tube are different, ion blank areas of different ion flows can reach a detector at the tail end of the migration tube at different moments, and an ion spectrogram with an ion current absolute value lower than a detection baseline is formed.
7. The method for controlling a super resolution ion mobility spectrometer according to claim 1, further comprising a sub positive and negative pulse cancellation operation, wherein the sub positive and negative pulse cancellation operation comprises:
due to the diffusion phenomenon and the existence of coulomb repulsion among ions, the ions in the ion sheet in the step one move to two sides of the sheet in the migration process, so that the thickness of the ion sheet is increased, and the detection result shows that the width of a spectrum peak is increased and the resolution is reduced; ions before and after the ion blank area in the step two move towards the ion blank area to influence the ion purity of the blank area, and the detection result shows that the height of a spectrum peak is reduced and the signal intensity is reduced;
subtracting the ion positive pulse spectrogram formed in the first step from the ion negative pulse spectrogram formed in the second step, and offsetting the influence of the diffusion phenomenon and the coulomb repulsion; for the ion sheet in the positive pulse sampling mode, the subtracted part is just the ions of the part of the ion cluster which diffuses outwards in the migration process, namely the subtracted part is the part of the ions of which the thickness of the ion sheet is widened due to the diffusion phenomenon and the coulomb repulsion, and the ion concentration of the central part of the ion sheet is not influenced, so that the resolution of the detection result is increased under the condition of not influencing the signal intensity.
8. A control system of a super resolution ion mobility spectrometer applying the control method of the super resolution ion mobility spectrometer according to any one of claims 1 to 7, the control system of the super resolution ion mobility spectrometer comprising:
the first ion spectrogram acquisition module is used for normally closing and momentarily opening the ion gate to obtain an ion spectrogram with a spectral peak higher than a base line;
the second ion spectrogram acquisition module is used for normally opening and temporarily closing the ion gate to obtain an ion spectrogram with a spectral peak lower than a baseline;
and the super-resolution ion spectrogram acquisition module is used for subtracting the ion spectrogram with the spectral peak higher than the baseline from the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
9. A computer device, characterized in that the computer device comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to carry out the steps of:
(1) the ion gate is normally closed and is opened temporarily to obtain an ion spectrogram with a spectral peak higher than a base line;
(2) the ion gate is normally opened and is closed temporarily to obtain an ion spectrogram with a spectral peak lower than a baseline;
(3) and (4) performing difference between the ion spectrogram with the spectral peak higher than the baseline and the ion spectrogram with the spectral peak lower than the baseline to obtain the super-resolution ion spectrogram.
10. An information data processing terminal characterized by being used for implementing the control system of the super-resolution ion mobility spectrometer according to claim 8.
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