CN104483378B - Reverse expansion HADAMARD transform ion mobility spectrometer - Google Patents

Abstract

The invention relates to an ion mobility spectrometer with reverse expansion HADAMARD transformation, comprising an ionization region, a curtain gas region, a reaction region, a reverse expansion HADAMARD transformation ion gating module, a migration region, a charge detection region, and an inverse HADAMARD transformation signal processing module. The ionization area has an ionization source, the curtain gas area is used to block the sample from entering the ionization area, and an ion gate is set between the reaction area and the migration area, and the ion gate is connected with the reverse expansion HADAMARD conversion gating module connected, the reverse expansion HADAMARD conversion gating module is used to periodically control the high-speed switch of the ion gate to realize the multiplexing of ion currents, and the charge detection area is connected with an inverse HADAMARD conversion signal processing module, the signal processing The module mainly completes the collection of multi-channel superimposed spectrum signals, A/D conversion, inverse HADAMARD transformation processing, and display of restored spectrum.

Description

A Reverse Extended HADAMARD Transformation Ion Mobility Spectrometer

technical field

The invention relates to an ion mobility spectrometer, in particular to a reverse expansion HADAMARD transformation ion mobility spectrometer.

Background technique

In recent years, various terrorist activities have been intensifying, both abroad and at home. In order to more effectively protect citizens' property and life safety, people have increased investment in research and development of rapid detection instruments for explosives, chemical warfare agents, and drugs. Mobility spectrometer, as a rapid trace chemical warfare agent detection equipment, is also in full swing.

Compared with other anti-riot and anti-terrorism detectors, the ion mobility spectrometer has the main advantage of being able to quickly detect some trace toxic gases, and distinguish the measured objects by using the different migration speeds of different ions under uniform and weak electric field conditions. Fast and high sensitivity. The ion mobility spectrometry detection device first appeared in the 1960s, and was mainly used in the military in the early days, mainly for the detection of trace chemical warfare agents. A large number of ion mobility spectrometers have also been invested in the security inspection departments of customs ports and other places to assist security inspection personnel to complete the rapid detection of trace explosives, drugs and chemical warfare agents.

The working mechanism of the corona discharge ion mobility spectrometer: in the discharge area, the high-purity _N2 or air is firstly discharged by the high-voltage module to generate reactant ions, and then the reactant ions enter the reaction area; in the reaction area, the reactant ions and The sample molecules entering the reaction zone through the carrier gas undergo a series of ion-molecule reactions, thereby ionizing the neutral sample molecules to form product ions. The ion gate connecting the reaction zone and the migration zone is periodically opened and closed. When the ion gate is opened, the product ions enter the migration zone. The migration zone has a uniform and stable weak electric field, which acts on the product ions to make them drift laterally. During the drift process, it collides with the oncoming neutral molecules of the migrating gas. Since different product ions have different masses, charges, and collision cross-section structures, they form different migration rates under the action of migration and collision, which is also It determines that different product ions arrive at the detector at different times, and finally realizes the effective separation of different ions.

With the continuous improvement of detection performance requirements, high resolution and high signal-to-noise ratio have become important technical indicators to measure the detection performance of ion mobility spectrometry. In order to improve the detection performance of ion mobility spectrometry, predecessors have done a lot of research. At the beginning of the 21st century, people tried to introduce HADAMARD multiplexing technology into ion mobility spectrometry, and successfully built a HADAMARD transform ion mobility spectrometer. The signal utilization rate of the ion mobility spectrum is improved, that is, the duty cycle, and the signal-to-noise ratio of the ion mobility spectrum is improved. Chinese patent CN200910051783.5 discloses an ion mobility spectrometer using the HADAMARD transformation method. Its ionization source uses a ⁶³ Ni radioactive ionization source, and uses a conventional pseudo-random sequence to control the ion gate, which improves the ion flux and signal-to-noise ratio. There are many false peaks in the HADAMARD transformed ion mobility spectrum generated by this method, and the ion mobility spectrum generated by this method cannot effectively improve the resolution of the ion mobility spectrum.

Therefore, it has become an inevitable trend in the research and development of ion mobility spectrometers to improve the signal-to-noise ratio and effectively improve the resolution of ion mobility spectrometers without large-scale changes in the hardware structure of ion mobility spectrometers. At present, there are few related literature reports.

Contents of the invention

The technical solution of the present invention: In view of the low resolution and signal-to-noise ratio of the traditional signal averaging method ion mobility spectrum, and the conventional HADAMARD transformation ion mobility spectrum can only improve the signal-to-noise ratio but not the resolution, a reverse expansion HADAMARD is proposed By changing the ion mobility spectrometer, the invention simultaneously improves the signal-to-noise ratio and resolution of the ion mobility spectrometer, and improves the comprehensive detection performance of the ion mobility spectrometer.

The technical solution of the present invention: a reverse expansion HADAMARD transformation ion mobility spectrometer, which includes an ionization zone, a curtain gas zone, a reaction zone, a reverse expansion HADAMARD transformation ion gating module, a migration zone, a charge detection zone, and an inverse HADAMARD transformation Signal processing module, there is an ionization source in the ionization zone, a curtain gas zone is set between the ionization zone and the reaction zone, and the curtain gas passed into the curtain gas zone can prevent sample gas from entering the ionization zone , the reaction zone and the migration interval are provided with an ion gate, characterized in that the ion gate is connected to the reverse expansion HADAMARD transformation ion gate control module, and the high-speed switch control of the ion gate is completed by the ion gate control module , the charge detection area is connected to the inverse HADAMARD transform signal processing module, and the signal processing module mainly completes the acquisition of superimposed spectra, A/D conversion, inverse HADAMARD transform processing, and display of restored spectra.

In one embodiment of the present invention, the ionization region adopts a negative high-voltage target plate discharge mode, and the ionization source is a negative high-voltage module whose output negative high voltage is -10000V.

In one embodiment of the present invention, the reaction zone and the migration zone are isolated by a BN-type ion gate, and the ion gate is connected to the reverse expansion HADAMARD gating module; in one embodiment of the present invention, the The reverse extension HADAMARD transformation ion gating module is composed of a pseudo-random sequence generator, an extension encoder, a reverse encoder and a boost module. First, a 255-bit pseudo-random binary sequence is generated by an 8-order pseudo-random sequence generator, which contains 128 1, 127 0s; the extended coder converts the 255-bit pseudo-random sequence into an extended pseudo-random sequence code of 255*4 (1020) bits; the reverse encoder converts the extended pseudo-random code Converted into a reverse-expanded pseudo-random sequence code, thereby obtaining an ion-gated digital sequence; the booster module converts the digital sequence (TTL level) into an ion-gated voltage signal of 0-220V, and the signal is directly connected to the ion gate ends. The modulation resolution (pulse width) of the ion gate is 200 μs.

In one embodiment of the present invention, the migration region is composed of a group of resistors with equal resistances connected in series evenly to provide a uniform weak electric field for ion movement, and the electric field in the migration region obtains a uniform weak electric field of 400V/cm by voltage division.

In one embodiment of the present invention, the charge detection area is composed of a charge detection board and a signal preprocessing unit, the charge detection board mainly converts the ion signal into a current signal, and the signal preprocessing unit uses an amplifier to convert the characterization The current signal of ionic strength is amplified and converted into a voltage signal.

Further, the inverse HADAMARD transform signal processing module completes the acquisition of HADAMARD transform superposition spectrum data, high-speed A/D conversion and inverse HADAMARD transform processing of migration spectrum. The data acquisition is controlled by a periodic pulse synchronization signal, which is consistent with the period of the reverse expansion pseudo-random sequence, and is controlled by the output of the reverse expansion HADAMARD ion gating module. The sampling frequency of the signal processing module is 20KHz, and the data The acquisition adopts the continuous acquisition mode, and the collected data is received in separate channels.

In one embodiment of the present invention, the ion mobility spectrometer works at normal temperature and pressure without adjusting the temperature and humidity of the ion mobility region.

Compared with the prior art, the present invention has the advantages that: a reverse expansion HADAMARD transformation ion mobility spectrometer of the present invention can not only effectively improve the ion flux, improve the signal-to-noise ratio, but also fully utilize the diffusion repulsion between ions to compress The full width at half maximum of the ion peak, thus effectively improving the resolution of the ion mobility spectrum. The present invention does not need to make major hardware changes to the existing ion mobility spectrometer; in terms of detection performance, compared with the traditional signal averaging method ion mobility spectrometry, the device of the present invention improves the detection signal-to-noise ratio by about 6.5 times, and improves the resolution The conventional HADAMARD transformation method can not improve the resolution of the ion mobility spectrum, which shows that the present invention is superior to the traditional signal averaging method and the conventional HADAMARD transformation method ion mobility spectrum in terms of comprehensive detection performance. In addition, the technical achievements of the present invention can also be used in other similar analysis techniques, and the application prospect is broad.

Description of drawings

Fig. 1 is a kind of reverse expansion HADAMARD transformation ion mobility spectrometer structure of the present invention;

Fig. 2 is the control schematic diagram of reverse expansion HADAMARD transformation ion gating module of the present invention;

Fig. 3 is the ion mobility spectrometry detection result of signal averaging method;

Figure 4 is a comparison chart of detection performance between conventional HADAMARD transformed ion mobility spectrometry and inverse extended HADAMARD transformed ion mobility spectrometer).

Among them, 1-ionization area, 2-curtain gas area, 3-reaction area, 4-reverse expansion HADAMARD transformation ion gating module, 5-migration area, 6-charge detection area, 7-inverse HADAMARD transformation signal processing module, 8-Negative high voltage module, 9-First gas outlet, 10-Curtain gas, 11-Second gas outlet, 12-Carrier gas inlet, 13-Ion gate, 14-Uniform transfer electric field, 15-Transfer gas inlet, 16- Faraday board, 17-signal preprocessing unit, 18-longest linear feedback shift register, 19-extended encoder, 20-reverse encoder, 21-boost module.

detailed description

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, a reverse expansion HADAMARD transformation ion mobility spectrometer, it includes ionization zone 1, curtain gas zone 2, reaction zone 3, reverse expansion HADAMARD transformation ion gating module 4, migration zone 5, charge detection Area 6. Inverse HADAMARD transform signal processing module 7. The ionization area adopts the negative corona discharge mode, and the negative high voltage module 8 of 10000V is used to output to the high voltage discharge needle, and through the plate type discharge mode, the incoming gas is ionized to generate reactant ions, and the first gas outlet is provided in the ionization area 9; the curtain gas zone utilizes the blown curtain gas 10 to prevent the sample gas from entering the ionization zone; the reaction zone is provided with a second gas outlet 11 and a carrier gas inlet 12; a BN is provided between the reaction zone and the migration zone Type ion gate 13, the ion gate is connected with the reverse expansion HADAMARD transformation ion gate control module 4 to realize the high-speed switch control of the ion gate; the migration area is alternately placed by a series of metal rings and polytetrafluoroethylene rings Each metal ring is connected through a uniform resistance to form a uniform migration electric field 14, and there is a migration gas inlet 15 at the end of the migration region for blowing back the neutral molecular gas to prevent it from reaching the Faraday plate; the charge detection region passes through the Faraday plate 16 detects the charge signal, and connects the signal to the signal preprocessing unit 17, completes the signal amplification and converts it into a 0-10V voltage signal; the inverse HADAMARD transformation signal processing module is connected to the charge detection area to realize the collection of superposition spectrum, A/D conversion, inverse HADAMARD conversion processing, display of restored spectrum.

Reversely extending the HADAMARD transformation gating module is the main innovation of the present invention. As early as 2006, foreign scholars have begun to explore multiplexed ion mobility spectrometry (IMS), and HADAMARD multiplexing technology has been introduced into IMS. Compared with the signal averaging method, the HADAMARD transformation using multiplexing technology IMS significantly improves the signal-to-noise ratio of the analytical instrument, but the disadvantage is that it cannot improve the resolution of the ion mobility spectrum at the same time, and there are false peaks in the inverse transform spectrum. For this reason, the present invention has done two aspects of processing, on the one hand is to isolate the pseudo-random sequence code, promptly carry out extension process, form the pseudo-random sequence code of extension (by adding extension code after each pseudo-random sequence code to realize), On the other hand, the extended pseudo-random sequence is reverse-coded, which is mainly for improving the resolution of the ion mobility spectrum.

The complete structure of the reverse extended HADAMARD transform ion gating module of the present invention is shown in FIG. 2 . In the embodiment, the 8th-order longest linear feedback shift register 18 is first constructed by FPGA, and its linear feedback logic expression is x ⁸ =x ⁴ +x ³ +x ² +1, and the length of the generated pseudo-random sequence is 255 bits ( 128 1s, 127 0s), and the duty cycle is about 50%. The pseudo-random sequence is converted into an extended pseudo-random sequence by the extension encoder 19, and three 0s are added after each pseudo-random sequence code. The duty cycle then drops to about 12.5%, and then the extended pseudo-random sequence is transformed into a reverse-extended pseudo-random sequence by the reverse encoder 20, and the duty cycle is raised to about 87.5%, and finally the boost module 21 converts the The reverse expansion pseudo-random sequence is converted into an ion gating pulse signal with a gate opening voltage of 0V and a gate closing voltage of 180V, which finally drives the switch of the ion gate (connected to both ends of the ion gate 13).

In the present invention, the pulse width (modulation resolution) of the ion gate 13 is selected as 200 μs.

In the present invention, the charge detection area uses the signal preprocessing unit to amplify the ion current detected by the Faraday plate and convert the current and voltage to obtain a voltage signal of 0-10V; the inverse HADAMARD transformation signal processing module first passes its own A/ The D conversion channel completes the acquisition, conversion, and storage of the superimposed spectrum data, and then performs inverse HADAMARD transformation processing, and displays the restored spectrum. Finally, the detection results of signal average method ion mobility spectrometry, conventional HADAMARD transform ion mobility spectrometry and reverse expansion HADAMARD transform ion mobility spectrometry were compared and analyzed. The spectrum of signal average method is shown in Figure 3. The spectra and the reverse extended HADAMARD transformed ion mobility spectra are shown in Fig. 4. The experimental results show that, taking the 255-bit pseudo-random sequence as an example, the conventional HADAMARD transforms the ion mobility spectrum, and its signal-to-noise ratio is about 1.58 times higher than that of the signal-averaged ion mobility spectrum, but its resolution is slightly smaller than that of the signal-averaged ion mobility spectrum. Spectrum; The present invention-reverse expansion HADAMARD transformation ion mobility spectrum is compared with the signal average method, and its signal-to-noise ratio is about 6.5 times of the signal average method, and the resolution has improved about 33% than the signal average method, and the comparison can be obtained, The comprehensive performance of the ion mobility spectrum of the reverse expansion HADAMARD transformation method proposed by the present invention is obviously better than the comprehensive detection performance of the conventional HADAMARD transformation ion mobility spectrum.

The above embodiments are provided only for the purpose of describing the present invention, not to limit the scope of the present invention. The scope of the invention is defined by the appended claims. Various equivalent replacements and modifications made without departing from the spirit and principle of the present invention shall fall within the scope of the present invention.

Claims (8)

1. A reverse expansion HADAMARD transformation ion mobility spectrometer, it comprises ionization zone (1), curtain gas zone (2), reaction zone (3), reverse expansion HADAMARD transformation ion gating module (4), migration zone (5), charge detection area (6), inverse HADAMARD transformation signal processing module (7); ionization source is arranged in described ionization area, and curtain gas area is arranged between described ionization area and described reaction area, and described curtain The gas zone can block the sample gas from entering the ionization zone, and the reaction zone and the migration zone are provided with a BN type ion gate (13), which is characterized in that: the ion gate is connected with the reverse expansion HADAMARD transformation ion gate Control module, the ion gate control module is used to periodically control the ion gate switch, complete the multiplexing of ion current signals, the charge detection area is connected with the inverse HADAMARD transformation signal processing module, the signal processing The module mainly completes the inverse HADAMARD transformation processing of the superimposed spectrum to obtain the restored spectrum; The reverse expansion HADAMARD transformation ion gating module (4) is made up of pseudo-random sequence generator (18), extension coder (19), reverse coder (20) and step-up module (21), at first consists of pseudo The random sequence generator constructs an n-order linear feedback shift register to obtain a 2 ⁿ -1-bit pseudo-random sequence; use the extended encoder to convert the pseudo-random sequence into an extended pseudo-random sequence code; then use the reverse encoder to extend the The pseudo-random code is converted into a reverse-expanded pseudo-random sequence code, thereby obtaining a periodic ion-gated digital sequence; the boost module is used to convert the ion-gated digital sequence into a voltage signal suitable for ion-gated control and connected to the Both ends of the ion gate to control the ion gate switch. 2. a kind of reverse expansion HADAMARD transformation ion mobility spectrometer according to claim 1, is characterized in that: described ionization region (1) adopts negative corona discharge mode, and ionization source is output by a negative high voltage module (8) The high voltage of 8700V～14000V reaches the corona discharge needle, and the reactant ions are obtained by aiming at the plate discharge mode. The ionization source can also be a photoionization source, a radioactive ionization source, or an electrospray ionization source. 3. A reverse expansion HADAMARD transformation ion mobility spectrometer according to claim 2, characterized in that: said radioactive ionization source is ⁶³ Ni. 4. a kind of reverse expansion HADAMARD transformation ion mobility spectrometer according to claim 1, is characterized in that: described ionization zone (1) and described reaction zone (3) are blocked by described curtain gas zone (2) , the curtain gas region is used to isolate the sample molecules from entering the ionization region. 5 . A reverse expansion HADAMARD transform ion mobility spectrometer according to claim 1 , characterized in that: the opening time of the ion gate is 50 μs to 600 μs, and the electric field strength of the migration is 260 to 500 V/cm. 6. A kind of reverse expansion HADAMARD transformation ion mobility spectrometer according to claim 1, it is characterized in that: described migration region (5) is made up of a series of metal rings and polytetrafluoroethylene rings alternately placed, by equivalent value The uniform resistance connects each metal ring to form a uniform migration electric field (14). 7. a kind of reverse expansion HADAMARD transformation ion mobility spectrometer according to claim 1, is characterized in that: described charge detection area comprises Faraday plate (16) and signal preprocessing unit (17), detects ion by Faraday plate The charge signal is connected to the signal preprocessing unit to complete ion current amplification and current/voltage signal conversion. 8. A kind of inverse extension HADAMARD transformation ion mobility spectrometer according to claim 1, is characterized in that: described inverse HADAMARD transformation signal processing module (7) carries out inverse HADAMARD to the stacked spectrum signal after the preprocessing of detection area Convert and process to obtain the restored migration spectrum data, and complete the display and comparison of the data.