CN113838738A

CN113838738A - Mass spectrum combined multi-channel electrospray micro-fluidic chip ion source

Info

Publication number: CN113838738A
Application number: CN202111074416.4A
Authority: CN
Inventors: 钱翔; 刘继琳; 余泉; 倪凯; 王晓浩
Original assignee: Shenzhen International Graduate School of Tsinghua University
Current assignee: Shenzhen International Graduate School of Tsinghua University
Priority date: 2021-09-14
Filing date: 2021-09-14
Publication date: 2021-12-24

Abstract

A mass spectrum combined multi-channel electrospray micro-fluidic chip ion source comprises a chip, a first liquid channel flow channel, a second liquid channel flow channel and a gas channel flow channel, wherein the first liquid channel flow channel and the second liquid channel flow channel are arranged in the chip, the gas channel flow channel is respectively matched with the first liquid channel flow channel and the second liquid channel flow channel, a first nozzle is formed at the junction of an outlet of the first liquid channel flow channel and an outlet of the corresponding gas channel flow channel, a second nozzle is formed at the junction of an outlet of the second liquid channel flow channel and an outlet of the corresponding gas channel flow channel, and an included angle between the first nozzle and the second nozzle is 45-55 degrees. The microfluidic chip ion source can effectively improve the signal intensity of mass spectra and improve the ionization efficiency, and is particularly suitable for desorbing samples by implementing a parallel ionization and spraying function.

Description

Mass spectrum combined multi-channel electrospray micro-fluidic chip ion source

Technical Field

The invention relates to an electrospray ion source, in particular to a mass spectrum combined multi-channel electrospray microfluidic chip ion source.

Background

With the widespread use of combinatorial chemistry in drug development, and the rapid development of clinical screening and proteomics research, a series of multi-channel ionization techniques aimed at achieving high-throughput analysis have emerged in succession. The multichannel simultaneous sample injection analysis mode is developed on the basis of electrospray ionization, electrospray is generated by a plurality of channels simultaneously, a larger spray volume is obtained, more ions are transmitted to enter a mass spectrum for detection, and the multichannel simultaneous sample injection analysis mode is commonly used for improving ionization efficiency and accurate mass analysis. The multichannel spraying can enhance the signal intensity, improve the sensitivity and realize the high-efficiency and high-throughput analysis of macromolecular samples. Mao et al designed a multi-nozzle circular array microfluidic chip, which processed multiple parallel nozzle groups on a circular silicon wafer, each nozzle group also containing a group of nozzle arrays.

Microfluidic chips with one-way channels such as the three-dimensional focusing microfluidic chip disclosed in CN 105498871A.

The mass spectrum adopts a mode of simultaneously sampling and analyzing by a multi-channel spray chip, a plurality of channels simultaneously generate electrospray to obtain larger spray volume, the multi-channel simultaneous sampling mode can be a multi-channel parallel mode, but the simple number superposition of the multi-channels does not mean that the signal sensitivity is enhanced.

It is to be noted that the information disclosed in the above background section is only for understanding the background of the present application and thus may include information that does not constitute prior art known to a person of ordinary skill in the art.

Disclosure of Invention

The invention mainly aims to overcome the defects of the background technology and provide a mass spectrum combined multi-channel electrospray microfluidic chip ion source.

In order to achieve the purpose, the invention adopts the following technical scheme:

a mass spectrum combined multi-channel electrospray micro-fluidic chip ion source comprises a chip, a first liquid channel flow channel, a second liquid channel flow channel and a gas channel flow channel, wherein the first liquid channel flow channel and the second liquid channel flow channel are arranged in the chip, the gas channel flow channel is respectively matched with the first liquid channel flow channel and the second liquid channel flow channel, a first nozzle is formed at the junction of an outlet of the first liquid channel flow channel and an outlet of the corresponding gas channel flow channel, a second nozzle is formed at the junction of an outlet of the second liquid channel flow channel and an outlet of the corresponding gas channel flow channel, and an included angle between the first nozzle and the second nozzle is 45-55 degrees.

Further:

the included angle between the spraying directions of the first nozzle and the second nozzle is 50 degrees.

The linear distance between the first nozzle and the second nozzle is 20-30 mm.

The linear distance between the first nozzle and the second nozzle is 25 mm.

Still include third liquid way runner, fourth liquid way runner and respectively with third liquid way runner with the gas circuit runner that the cooperation of fourth liquid way runner set up, the export of third liquid way runner and the export of corresponding gas circuit runner meet the department and form the third nozzle, the export of fourth liquid way runner and the export of corresponding gas circuit runner meet the department and form the fourth nozzle, the third nozzle with the fourth nozzle sets up first nozzle with between the second nozzle, just the third nozzle with the blowout direction of fourth nozzle with the central line of contained angle is parallel.

The third nozzle and the fourth nozzle are symmetrically distributed on two sides of the center line of the included angle.

A mass spectrometry system comprises a mass spectrometer and the mass spectrometry combined multi-channel electrospray micro-fluidic chip ion source.

Further:

the mass spectrum sample inlet is arranged below the chip, the first nozzle and the second nozzle of the chip are downwards inclined to align with a sample point in front of the mass spectrum sample inlet, and the inclination angle between the chip and the horizontal plane is 15-25 degrees.

The inclination angle between the chip and the horizontal plane is 20 degrees.

The position of the sample point is lower than the mass spectrum injection port, the horizontal distance between the sample point and the mass spectrum injection port is 10 +/-2 mm, and the vertical distance is 3 +/-1 mm.

The invention has the beneficial effects that:

the inventor researches and discovers that the microfluidic chip multi-channel ion source is influenced by a space structure, wherein the position structure between nozzles inside the chip is the key of the system space structure. Taking a dual-channel electrospray microfluidic chip desorption ion source as an example, the position between two nozzles in the chip, the space distance between a sample point and a mass spectrum sample inlet and the like are all factors influencing the efficiency of the sample entering mass spectrum analysis.

The invention provides a multi-channel electrospray micro-fluidic chip as a mass spectrometry ion source, which optimizes space structure parameters between two nozzles and a sample spot of the multi-channel chip, wherein an included angle between the spraying directions of a first nozzle and a second nozzle is 45-55 degrees, spray generated between the two nozzles can extract or desorb a sample under the optimal spraying condition, and the influence of an airflow field and an electric field between the nozzles on electrospray is reduced as much as possible. In a further preferred embodiment, the angle between the two nozzles, the inclination angle between the chip and the horizontal plane, and the horizontal distance and the vertical distance between the sample point and the mass spectrum sample inlet are jointly optimized, so that the spatial parameters reach a good synergistic relationship in the mass spectrum process, and the optimal mass spectrum detection effect can be obtained. The chip of the invention is particularly suitable for carrying out parallel ionization and spraying functions to desorb samples.

The multiple channels of the microfluidic chip multi-channel ion source simultaneously generate electrospray and mass spectrum combined sample injection, the ionization efficiency is high, and the microfluidic chip multi-channel ion source can be used as an open type ion source such as an electrospray ion source (ESI), a desorption electrospray ion source (DESI) and an extraction electrospray ion source (EESI). The microfluidic chip ion source can be used for simultaneously manufacturing a plurality of microchannels to realize a parallel ionization spraying function in the process, can also finish the pretreatment work of complex samples, such as sample purification, separation, desalination and the like, and is beneficial to the development and extension of high-throughput analysis.

Drawings

Fig. 1A is a schematic plan view of a multi-channel electrospray microfluidic chip according to an embodiment of the invention.

Fig. 1B is a schematic plan view of a multi-channel electrospray microfluidic chip according to another embodiment of the invention.

FIG. 2 is a schematic diagram of a serpentine channel and a trumpet-shaped opening of a multi-channel microfluidic chip according to an embodiment of the present invention;

FIG. 3 is a schematic view of a microfluidic chip processing flow according to an embodiment of the present invention;

FIG. 4 is a diagram of a multi-channel electrospray microfluidic chip according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a simulation structure and a grid of a dual-channel microfluidic chip desorption ion source according to an embodiment of the present invention, wherein: (a) abstracting a simulation area; (b) simulating a structure; (c) grid division;

fig. 6 is a simulation flow chart of a dual-channel microfluidic chip desorption ion source according to an embodiment of the present invention, wherein: (a) is a flow chart when the pathlines is 500 steps, and (b) is a flow chart when the pathlines is 4000 steps;

fig. 7 is a mass spectrogram of 4.8mg/L urine matrix rhodamine B according to an embodiment of the present invention, (a) a total ion flow graph with a peak of 443.4 m/z, which includes three stages of (i) - (iii), i.e., single-path spraying + single-path pressurized high-speed airflow, and two-path spraying; (b) stage two, mass spectrogram; (c) stage III mass spectrogram.

Detailed Description

The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for either a fixed or coupled or communicating function.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the embodiments of the present invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be in any way limiting of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to fig. 1A, fig. 1B and fig. 5, an embodiment of the present invention provides a mass spectrum combined multi-channel electrospray microfluidic chip ion source, including a chip 1, a first liquid channel 11 and a second liquid channel 12 disposed in the chip, and

gas channel channels

21 and 22 respectively disposed in cooperation with the first liquid channel 11 and the second liquid channel 12, where a junction between an outlet of the first liquid channel 11 and an outlet of the corresponding gas channel 21 forms a first nozzle 31, a junction between an outlet of the second liquid channel 12 and an outlet of the corresponding gas channel 22 forms a second nozzle 32, and an included angle β between ejection directions of the first nozzle 31 and the second nozzle 32 is 45 ° to 55 °. In a particularly preferred embodiment, the angle β between the ejection directions of the first nozzle 31 and the second nozzle 32 is 50 °.

In a further preferred embodiment, the linear distance d between the first nozzle 31 and the second nozzle 32 is 20 to 30 mm. In a particularly preferred embodiment, the linear distance d between the first nozzle 31 and the second nozzle 32 is 25 mm.

Referring to fig. 1B, in a preferred embodiment, the liquid supply device further includes a third liquid path flow passage 13, a fourth liquid path flow passage 14, and air

path flow passages

23 and 24 respectively matched with the third liquid path flow passage 13 and the fourth liquid path flow passage 14, a third nozzle 33 is formed at a junction of an outlet of the third liquid path flow passage 13 and an outlet of the corresponding air path flow passage 23, a fourth nozzle 34 is formed at a junction of an outlet of the fourth liquid path flow passage 14 and an outlet of the corresponding air path flow passage 24, the third nozzle 33 and the fourth nozzle 34 are disposed between the first nozzle 31 and the second nozzle 32, and an ejection direction of the third nozzle 33 and the fourth nozzle 34 is parallel to a center line of the included angle.

In a more preferred embodiment, the third nozzle 33 and the fourth nozzle 34 are symmetrically distributed on both sides of the center line of the included angle.

The embodiment of the invention also provides a mass spectrum system which comprises a mass spectrometer and the mass spectrum combined multi-channel electrospray micro-fluidic chip ion source.

Referring to fig. 5, in a preferred embodiment, the mass spectrometer inlet is disposed below the chip, the first nozzle 31 and the second nozzle 32 of the chip are inclined downward to be aligned with a sample point in front of the mass spectrometer inlet, and an inclination angle α between the chip and a horizontal plane is 15 ° to 25 °.

In a preferred embodiment, the chip is inclined at an angle of 20 ° to the horizontal.

In a preferred embodiment, the sample point is located below the mass spectrometry injection port, the horizontal distance l between the sample point and the mass spectrometry injection port is 10 +/-2 mm, and the vertical distance h is 3 +/-1 mm. The sample point is the central point of the sample spot, the spray sprayed by the nozzle falls on the sample spot, and enters the mass spectrum sample inlet after rebounding.

The multi-channel electrospray micro-fluidic chip provided by the invention is used as a mass spectrum ion source, the space structure parameters between two nozzles and a sample spot of the multi-channel chip are optimized, the spray generated between the two nozzles can extract or desorb the sample under the optimal spraying condition, and the influence of an airflow field and an electric field between the nozzles on electrospray is reduced as much as possible. The chip of the invention is particularly suitable for carrying out parallel ionization and spraying functions to desorb samples.

Specific embodiments of the present invention are further described below.

According to the research of the microfluidic chip, the microfluidic network is analogized to an analog circuit network, the series-parallel connection, the partial pressure, the node current and the loop voltage rule of impedance in the circuit are also applicable to a microfluidic channel, the liquid resistance of each gas channel in the multichannel chip is ensured to be the same based on the NaviStokes equation in fluid mechanics, the liquid resistance is symmetrically distributed on two sides of the chip, the effect of the chip is not influenced after gas channels are combined, and the problem of the quantity requirement of an external fluid driving system can be reduced.

In the design of the multi-channel chip liquid path flow channel, as shown in fig. 2, the linear flow channel can be designed as a snake-shaped flow channel, so that the resistance of the liquid path flow channel is improved, and the liquid path retraction caused by the extrusion of the gas path is prevented; the horn-shaped opening is designed at the outlet of the chip, so that the nozzle is formed in the chip, the damage to the nozzle caused by cutting can be avoided, the liquid drop suspension can be prevented to a certain extent, and the quality of spray forming is improved.

Processing technology of micro-fluidic chip

The microfluidic chip is of a three-dimensional focusing type, is provided with a shallow liquid path and a deep gas path, and is made of an upper PDMS chip key and a lower PDMS chip key, wherein the liquid path only exists in the upper chip, the gas path is symmetrically distributed in the upper chip and the lower chip, and the key and the gas path symmetrically wrap the liquid path in the middle to form the three-dimensional focusing type microfluidic chip.

Selecting SU-8 photoresist as a mold material, and processing the SU-8 photoresist by using a soft lithography process to form a chip mold with a runner structure; PDMS is used as a chip material, and a chip is manufactured by bonding and other processes, and the processing flow is shown in FIG. 3. The micro-fluidic chip processing comprises three main steps of chip die manufacturing (1-2), chip manufacturing (3-4) and chip key and (5), namely, dies of an upper chip and a lower chip are manufactured respectively, then the upper chip and the lower chip are manufactured by die reversing of the dies, and finally the upper chip and the lower chip are aligned to the key and formed, and the die and the chip manufacturing process taking the upper chip as an example are shown in fig. 3.

The equipment used for processing mainly comprises a mask plate, a spin coater, a photoetching machine, an oxygen plasma processor and the like, and the reagents used in the process mainly comprise SU-8 photoresist, developing solution, PDMS and the like.

Soft photoetching process of micro-fluidic chip

The photoetching process flow comprises whirl coating, prebaking, exposure, postbaking, development and hardening in detail, if the multilayer structure is prepared, the whirl coating, prebaking, exposure, postbaking and development procedures can be repeatedly carried out, or only the whirl coating, prebaking, exposure and postbaking procedures can be repeatedly carried out, and finally the mold is hardened by one-time development. From the operation and experimental effect, the last one-time development mode has the advantages of simpler operation, time saving and difficulty in causing the photoresist to fall off. The specific flow of the two-layer structure lithography process of the gas circuit layer and the liquid circuit layer is described in detail below.

1) Spin coating: firstly, a 3-inch silicon wafer is stably fixed on a vacuum chuck of a spin coater, a dropper is used for taking a proper amount of SU-82025 photoresist at the center of the silicon wafer, the photoresist is coated for 10 seconds at a rotating speed of 1000 rpm, and then the photoresist is coated for 30 seconds at a rotating speed of 3000 rpm, so that the photoresist can be prevented from being thrown out in sudden rapid rotation in a layered rotation manner, and the photoresist is not uniformly distributed on the silicon wafer. If the prepared micro-channel is deep, oxygen plasma can be applied to the silicon chip substrate for 30 seconds before photoresist throwing, so that the photoresist is prevented from falling off from the silicon chip after developing;

2) pre-baking: and transferring the silicon wafer containing the photoresist to a hot plate, firstly drying at 65 ℃ for 5 minutes, then drying at 95 ℃ for 10 minutes, completing prebaking, and air-cooling to room temperature. The solvent in the photoresist can be evaporated by prebaking to make the photoresist hard, so that the phenomenon that the photoresist is adhered to the mask plate in the contact exposure process, the thickness and the uniformity of the photoresist layer are damaged, and the mask plate is polluted is avoided;

3) exposure: placing the silicon wafer subjected to pre-baking air cooling on a moving platform of an ultraviolet photoetching machine, then lightly pasting a liquid path layer mask plate on the photoresist (the mask plate is not placed reversely), keeping the appearance coincidence of the silicon wafer and the mask plate, clamping and fixing, setting the exposure time to be 18 seconds, and starting exposure; the exposure is mainly aimed at irradiating SU-8 photoresist by ultraviolet light to generate photoacid, and after a post-baking process, the irradiated photoresist undergoes a crosslinking reaction to generate a substance insoluble in a developing solution, thereby forming a flow channel structure. The exposure time determines the forming effect of the photoresist under the condition of fixed power of the photoresist. The thicker the photoresist is, the longer the relatively required exposure time is;

4) post-baking: after the exposure, the silicon wafer was placed on a hot plate, baked at 65 ℃ for 5 minutes, then baked at 95 ℃ for 10 minutes, and then post-baked, and then cooled to room temperature. The post-baking mainly makes the exposed photoresist generate cross-linking reaction inside so as to solidify and form the micro-channel structure. In order to reduce the internal stress of the photoresist, the post-baking time can be properly increased or decreased, and the post-baking temperature can be reduced. Thus, completing the photoetching process of the liquid path layer;

5) spin coating: and fixing the silicon wafer after the first exposure on a vacuum chuck of a spin coater again, taking a proper amount of SU-82100 photoresist at the center of the silicon wafer by using a dropper, and spin-coating the photoresist at the rotating speed of 1000 revolutions per minute for 10 seconds, and then spin-coating the photoresist at the rotating speed of 1500 revolutions per minute for 30 seconds. The rotation speed is mainly determined by the thickness of the spin coating, i.e. the depth of the processing flow channel. The second layer of the upper piece of the three-position focusing chip is an air path layer, and an air path flow channel is required to be deeper, so that the spin glue is thicker and the rotating speed is lower;

6) pre-baking: the silicon wafer containing the photoresist was transferred to a hot plate and baked at 65 ℃ for 5 minutes and then at 95 ℃ for 60 minutes. Because the photoresist is thicker, the prebaking time of the photoresist must be increased to further cure the photoresist, so that the adhesion of the photoresist and the mask is prevented;

7) exposure: placing the silicon wafer subjected to pre-baking air cooling on a moving table of an ultraviolet photoetching machine, then lightly pasting a gas circuit layer mask plate on the photoresist, aligning a mark on the gas circuit layer mask plate with a liquid circuit layer mark formed on the photoresist by means of a microscope on the photoetching machine, clamping and fixing, setting the exposure time to be 30 seconds, and starting exposure, wherein the exposure time is increased due to the fact that the photoresist is thick;

8) post-baking: after exposure, the silicon wafer is placed on a hot plate, is dried for 5 minutes at 65 ℃, is dried for 10 minutes at 95 ℃, is dried after completion, and is cooled to room temperature; completing the photoetching process of the gas circuit layer;

9) and (3) developing: placing the silicon wafer subjected to twice exposure in a culture dish filled with a developing solution to ensure that the developing solution can completely immerse the silicon wafer, shaking the culture dish in a fume hood, taking out the silicon wafer after the micro-channel structure is completely shown and part of photoresist which does not undergo a crosslinking reaction is completely removed, washing the silicon wafer with ethanol, and finally drying the solvent on the silicon wafer by using nitrogen. The developed silicon chip has formed the needed micro-channel structure composed of SU-8;

10) hardening the film: and (3) placing the developed silicon wafer in an oven, and baking for 30 minutes at 120 ℃, or reducing the temperature and increasing the baking time, so that the hardness of the photoresist is increased, and the bonding strength between the photoresist and the silicon wafer is enhanced.

The above is a detailed photolithography process for processing the double-layer micro-channel structure, if three-layer photolithography is required, the above steps 1) -4) are repeated again, and finally, development hardening is performed to complete the fabrication of one-piece structure. In most biological applications, PDMS is bonded to glass, silicon wafers, etc. to form a complete chip, and the micro-channel structure of the whole chip is on the PDMS material. If the bonded upper and lower PDMS materials need different runner structures, a lower template structure needs to be processed again according to the above steps.

PDMS material micro-fluidic chip processing technology

And photoetching a finished chip mold with a micro-channel structure on a silicon chip substrate, performing reverse molding by using a PDMS material, and finally bonding to finish the manufacturing of the chip. And the two PDMS sheets which are bonded up and down on the three-dimensional focusing microfluidic chip are both provided with a micro-channel structure, so that the bonding form of the PDMS and the PDMS sheets is mainly adopted. The specific processing steps of the microfluidic chip made of PDMS are as follows.

1) Preparing glue: a certain proportion of curing agent needs to be mixed in PDMS to adjust the hardness of the chip. The upper and lower chips of the chip are generally fabricated by selecting the ratio of PDMS prepolymer to curing agent as 1:10 and 1:5, respectively. The upper sheet needs to be perforated, so that the rigidity is low. The two ratio chips can withstand large gas flow impacts on the order of megapascals. After blending, stirring the mixture, and placing the mixture in a vacuum drying oven to remove bubbles;

2) entering a mold: and respectively pouring the PDMS without the bubbles into the molds of the upper and lower pieces, wherein the pouring thickness is not too thick and the holes are easy to punch, and the thickness of the upper and lower pieces of the designed chip is about 1 cm. Putting the PDMS into the mold again into a vacuum drying box for air suction, and then taking out and slightly blowing off bubbles on the surface of the PDMS by using an ear washing ball;

3) and (3) hot baking and curing: placing the gas-removed PDMS mixture together with the culture dish in an oven at 80 ℃ for baking for 30 minutes to finish the curing of PDMS;

4) demolding: taking out the cured mold containing the PDMS, and cutting the mold along an outer frame formed on the PDMS by using a blade, namely demolding the PDMS;

5) cutting and punching: cutting the demolded PDMS along the edge of the chip structure, particularly paying attention to avoid damaging a chip spray nozzle during cutting, and punching and opening holes at gas and liquid path inlets reserved on an upper chip core after cutting;

6) cleaning and bonding and: cleaning the upper PDMS piece and the lower PDMS piece with ethanol, and then placing the cleaned PDMS pieces into an oxygen plasma cleaning machine for surface plasma treatment to enhance bonding strength. Finally, aligning the upper PDMS sheet and the lower PDMS sheet with keys by using a microscope to form a complete micro-fluidic chip;

7) and (3) baking: and placing the bonded microfluidic chip in a constant-temperature drying oven at 80-120 ℃ for over 24 hours, reinforcing the upper and lower chip keys and strength, and eliminating the background noise of the PDMS material.

The above steps are the whole process for manufacturing the microfluidic chip, and if a plurality of microfluidic chips need to be repeatedly manufactured, the microstructure template finished by photoetching is only required to be repeatedly used, and the seven steps of microfluidic chip processing technological processes are repeatedly carried out. The mode of repeatedly using the same template to process the microfluidic chip greatly improves the working efficiency and reduces the material cost. The schematic plan view of the structure of the multi-channel three-dimensional focusing microfluidic chip is shown in fig. 1A and 1B, and the actual view is shown in fig. 4.

Dual-channel electrospray chip desorption ion source and mass spectrum combined simulation analysis

The FLUENT simulation software is adopted to simulate and analyze the area flow fields of two nozzles inside the chip and the sample spots, space parameters between the chip and the sample spots are optimized, experiments prove that the structure can realize efficient parallel ionization spray function desorption of samples, the mass spectrum signal intensity is optimal when the included angle between the nozzles is about 50 degrees, and the ionization efficiency is improved.

FLUENT simulation condition setting

The single-channel chip is simplified into a speed inlet model with zero liquid channel flow velocity and only a gas channel, a mass spectrum sample inlet can open certain sheath gas flow velocity in a mass spectrum experiment, and the sheath gas flow is about 0.8L/min when the mass spectrum sample inlet is set to be 1arb, so that the mass spectrum sample inlet is simplified into a speed inlet with negative speed in simulation. In summary, the flow field simulation region is abstracted into a structure body with a plurality of chip velocity input ports and a mass spectrum negative velocity input port.

The space structure parameters mainly comprise an inclination angle alpha between the chip and the horizontal plane, an included angle beta between the two spray nozzles, a horizontal distance l between a sample point and a mass spectrum sample inlet, a vertical distance h and a linear distance d between the two spray nozzles, and the structure bodies with different space structures are built by adjusting the five parameters. The space structure body is drawn by AutoCAD software, then gridding is carried out by using Gambit software, and finally simulation is carried out by using Fluent software. The structure and grid are shown in figure 5.

Through the optimization of multiple experiments, the optimized spatial structure parameters are obtained, as shown in the table 3.

TABLE 3 Dual-channel electrospray microfluidic chip desorption ion source space structure parameter table

After the structure is drawn, gridding is carried out by utilizing Gambit software, and the setting parameters of the grid are as follows: the grid element Elements are Hex, type is Submap, grid size is 0.5. After the grid drawing is finished, flow field simulation is carried out by using FLUENT software, two nozzles of an inlet1 and an inlet2 of a chip are set as a velocity entrance boundary velocity-inlet of a simulation structure, and the velocity is set to be about 20 m/s; and setting the mass spectrum sample inlet as a velocity inlet velocity-inlet with the velocity of-2 m/s. Considering the high flow rate of the gas stream, the calculation is carried out by using a k-epsilon (2-eqn) model.

FLUENT simulation results

The flow velocity profile of the simulation result is shown in fig. 6. Fig. 6(a) is a flow chart when the pathlines is 500 steps, and fig. 6(b) is a flow chart when the pathlines is 4000 steps. As can be seen from fig. 6(a), the flow field in the region above the sample point of the sample spot filter paper is in a vortex form, and the flow velocity is highest at the sample point. As seen in fig. 6(b), the fluid enters the mass spectrometer inlet.

The mass spectrum experiment result is introduced later, and the multichannel structure space configuration is verified to have good detection performance, so that the mass spectrum signal intensity is effectively improved, and the ionization efficiency is improved.

Double-channel electrospray chip desorption ion source and mass spectrum combined experimental test

By adopting the two-channel electrospray chip with the spatial structure, high-concentration graphene oxide GO membrane filter paper with the concentration of 6.2g/L is used as a dry sample spot paper substrate in an experiment; the effect of the dual-channel chip desorption ion source was tested by using 4.8mg/L urine matrix rhodamine B (mass-to-charge ratio 443.4) as a sample solution and a solution of 80% methanol-water mixed with 0.1% formic acid as a solvent.

In the experiment, one path of gas and liquid paths is firstly opened, the flow rate of the liquid path is 8 mu L/min, then the additional 5kV high voltage is opened to generate single-path electrospray, the generated electrospray is sprayed and aligned to a sample point of filter paper, mass spectrum signals of desorption ionization are recorded, and then the second path is opened to record mass spectrum signals of double-channel ionization. As shown in fig. 7, the detected total ion flow graph includes three stages of (r) - (c): stage I is the situation that only the nozzle 1 generates the electrospray; the gas path and voltage of the nozzle 2 are opened at about 0.5 minute to form a corresponding mass spectrum signal diagram as shown in (b) of FIG. 7, and the signal intensity is increased to 8 × 10³(ii) a At about 1.2 minutes of recording, the liquid path of the nozzle 2 is opened to make two paths of electric sprays work simultaneously to form a third stage, at which the corresponding mass spectrum signal diagram is shown in (c) of figure 7,the signal intensity is increased to 3 x 10⁴The sample is more fully ionized. Two-path spraying enables more charged ions to impact on a sample point, the desorption probability is increased, the ionization efficiency is improved, the detection signal intensity is improved by more than 1 magnitude order, and the improvement on the mass spectrum detection performance is obvious.

The background of the present invention may contain background information related to the problem or environment of the present invention and does not necessarily describe the prior art. Accordingly, the inclusion in the background section is not an admission of prior art by the applicant.

The foregoing is a more detailed description of the invention in connection with specific/preferred embodiments and is not intended to limit the practice of the invention to those descriptions. It will be apparent to those skilled in the art that various substitutions and modifications can be made to the described embodiments without departing from the spirit of the invention, and these substitutions and modifications should be considered to fall within the scope of the invention. In the description herein, references to the description of the term "one embodiment," "some embodiments," "preferred embodiments," "an example," "a specific example," or "some examples" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the claims.

Claims

1. The multi-channel electrospray micro-fluidic chip ion source for mass spectrum combination is characterized by comprising a chip, a first liquid channel flow channel, a second liquid channel flow channel and a gas channel flow channel, wherein the first liquid channel flow channel and the second liquid channel flow channel are arranged in the chip, the gas channel flow channel is respectively matched with the first liquid channel flow channel and the second liquid channel flow channel, a first nozzle is formed at the junction of an outlet of the first liquid channel flow channel and an outlet of the corresponding gas channel flow channel, a second nozzle is formed at the junction of an outlet of the second liquid channel flow channel and an outlet of the corresponding gas channel flow channel, and an included angle between the first nozzle and the second nozzle is 45-55 degrees.

2. The mass spectrometry multi-channel electrospray microfluidic chip ion source of claim 1, wherein the angle between the ejection directions of the first nozzle and the second nozzle is 50 °.

3. The mass spectrometry multi-channel electrospray microfluidic chip ion source according to claim 1 or 2, wherein the linear distance between the first nozzle and the second nozzle is 20-30 mm.

4. The mass spectrometry multi-channel electrospray microfluidic chip ion source of claim 3, wherein the linear distance between the first nozzle and the second nozzle is 25 mm.

5. The ion source of any one of claims 1 to 4, further comprising a third liquid channel flow channel, a fourth liquid channel flow channel, and a gas channel flow channel respectively matched with the third liquid channel flow channel and the fourth liquid channel flow channel, wherein a junction of an outlet of the third liquid channel flow channel and an outlet of the corresponding gas channel flow channel forms a third nozzle, a junction of an outlet of the fourth liquid channel flow channel and an outlet of the corresponding gas channel flow channel forms a fourth nozzle, the third nozzle and the fourth nozzle are disposed between the first nozzle and the second nozzle, and an ejection direction of the third nozzle and the fourth nozzle is parallel to a center line of the included angle.

6. The mass spectrometry multi-channel electrospray microfluidic chip ion source of claim 5, wherein the third nozzle and the fourth nozzle are symmetrically distributed on both sides of the centerline of the included angle.

7. A mass spectrometry system comprising a mass spectrometer and a mass spectrometry coupled multi-channel electrospray microfluidic chip ion source as claimed in any of claims 1 to 6.

8. The mass spectrometry system of claim 7, wherein the mass spectrometer inlet is disposed below the chip, the first nozzle and the second nozzle of the chip are tilted downward to align with a sample point in front of the mass spectrometer inlet, and the tilt angle between the chip and a horizontal plane is 15 ° to 25 °.

9. The mass spectrometry system of claim 8, wherein the chip is tilted at an angle of 20 ° to the horizontal.

10. The mass spectrometry system of claim 8 or claim 9, wherein the sample point is located below the mass spectrometry inlet port at a horizontal distance of 10 ± 2mm and a vertical distance of 3 ± 1 mm.