A multi-channel electrospray microfluidic chip and its application

Abstract

The present invention discloses a multi-channel electrospray microfluidic chip and its application, which includes two first gas phase flow channels and at least two liquid phase flow channels, wherein the liquid phase flow channels are arranged between the two first gas phase flow channels; the nozzle of the first gas phase flow channel is arranged at an interval with the nozzle of the liquid phase flow channel. In the process of electrospraying, the relative position of the liquid phase nozzle and the first gas phase nozzle is fixed, and the spraying conditions are stable and consistent. On the one hand, the extraction function of macroscopic electrospraying can be realized, and the extraction efficiency and extraction effect of the extracting liquid on the test liquid can be improved, which is conducive to the rapid detection of complex samples; on the other hand, it solves the problem that it is difficult to electrospray two or more liquid paths at the same time, and finally creates more application forms for the combination of microfluidic chips and mass spectrometers, which can be widely used in many aspects such as rapid mixing reaction of substances, protein folding and stretching analysis, and internal standard testing.

Description

Technical Field

[0001] The invention relates to the field of microfluidic chips for electrospray, and in particular to a multi-channel electrospray microfluidic chip and applications thereof. Background Art

[0002] For mass spectrometry analysis, single-channel sample ionization can no longer meet the needs of related tests, and dual-channel or even multi-channel ionization has become a research hotspot. Dual-channel or multi-channel spray ion sources can be used in many aspects, such as accurate mass determination through dual-channel internal standards, extraction and detection of complex samples through dual-channel spray, and multi-channel spray to enhance signal strength and improve sensitivity, which are all functions that cannot be achieved by single-channel spray.

[0003] In the application research of dual-path spray, the extractive electrospray ion source (EESI) plays an important role in mass spectrometry analysis. Because when complex samples such as urine, serum, lake water and milk are directly sprayed into the mass spectrometer for signal detection using an electrospray ion source, it will quickly lead to the formation of adducts, sample residues and accumulation of non-volatile substances, which will eventually cause the sensitivity of the mass spectrometer to decrease rapidly and be difficult to recover. EESI can achieve rapid online detection of complex samples such as urine, milk and other substances without any sample pretreatment process.

[0004] However, when EESI is used for dual-path extraction spray, the placement and angle of the two nozzles will affect the stability and sensitivity of the test, usually resulting in low extraction efficiency and poor ionization effect of the liquid to be tested, thus resulting in weak test signals and poor experimental operability and reproducibility.

[0005] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a multi-channel electrospray microfluidic chip and its application, aiming to improve the extraction efficiency and effect of mass spectrometry test liquid, thereby enhancing the test signal of the mass spectrometer for the liquid to be tested.

[0007] The technical solution of the present invention is as follows:

[0008] A multi-channel electrospray microfluidic chip, comprising: two first gas phase flow channels and at least two liquid phase flow channels; the liquid phase flow channels are arranged between the two first gas phase flow channels; the nozzles of the first gas phase flow channels are spaced apart from the nozzles of the liquid phase flow channels.

[0009] The multi-channel electrospray microfluidic chip further comprises at least one second gas phase flow channel located between the at least two liquid phase flow channels, and the nozzle of the second gas phase flow channel is spaced apart from the nozzle of the liquid phase flow channel.

[0010] The multi-channel electrospray microfluidic chip, wherein the other end of each of the liquid phase flow channels is provided with a liquid phase inlet.

[0011] The multi-channel electrospray microfluidic chip, wherein the two first gas phase flow channels and the other end of the second gas phase flow channel converge to form a gas phase dry flow channel, and a gas phase inlet is provided at the end of the gas phase dry flow channel.

[0012] The multi-channel electrospray microfluidic chip, wherein the nozzles of two adjacent liquid phase flow channels are arranged at intervals.

[0013] In the multi-channel electrospray microfluidic chip, the interval between the nozzle of the first gas phase flow channel and the nozzle of the liquid phase flow channel and the interval between the nozzle of the second gas phase flow channel and the nozzle of the liquid phase flow channel are both 10-100 μm.

[0014] In the multi-channel electrospray microfluidic chip, central axes of the nozzles of the liquid phase flow channel, the first gas phase flow channel and the second gas phase flow channel are parallel, and the nozzles are all on the same plane.

[0015] The multi-channel electrospray microfluidic chip, wherein the depths of the first gas phase flow channel and the second gas phase flow channel are greater than the depth of the liquid phase flow channel.

[0016] The multi-channel electrospray ionization microfluidic chip is made of PDMS or PMMA.

[0017] An application of the multi-channel electrospray microfluidic chip as described above, wherein the multi-channel electrospray extraction microfluidic chip is used for liquid extraction electrospray or for simultaneous electrospray of multiple liquid paths.

[0018] Beneficial effects: The present invention provides a multi-channel electrospray microfluidic chip, which includes two first gas phase flow channels and at least two liquid phase flow channels, wherein the liquid phase flow channels are arranged between the two first gas phase flow channels; the nozzle of the first gas phase flow channel is arranged at an interval with the nozzle of the liquid phase flow channel. In the process of electrospraying, the relative position of the liquid phase nozzle and the first gas phase nozzle is fixed, and the spraying conditions are stable and consistent. On the one hand, the extraction function of macroscopic electrospraying can be realized, and the extraction efficiency and extraction effect of the extracting liquid on the test liquid can be improved, which is conducive to the rapid detection of complex samples; on the other hand, it solves the problem that it is difficult to electrospray two or more liquid paths at the same time, and finally creates more application forms for the combination of microfluidic chips and mass spectrometers, which can be widely used in many aspects such as rapid mixing reaction of substances, protein folding and stretching analysis, and internal standard testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of a first embodiment of a multi-channel electrospray microfluidic chip of the present invention.

[0020] Figure 2 This is a schematic structural diagram of a second embodiment of a multi-channel electrospray microfluidic chip of the present invention.

[0021] Figure 3 This is a schematic structural diagram of a third embodiment of a multi-channel electrospray microfluidic chip of the present invention.

[0022] Figure 4 This is a schematic structural diagram of a fourth embodiment of a multi-channel electrospray microfluidic chip of the present invention.

[0023] Figure 5 Schematic diagram of mixed Taylor cone spray formation.

[0024] Figure 6 Schematic diagram of the formation of separated Taylor cone spray.

[0025] Figure 7a The mass spectrum of rhodamine B in urine solution tested using the EESI ion source.

[0026] Figure 7b The mass spectrum of the urine solution of Rhodamine B tested using the first embodiment of the present invention.

[0027] Figure 8 FIG. 4 is a graph showing the stability of the total ion current using the spray of the third embodiment of the present invention.

[0028] Figure 9a This is the mass spectrum of Rhodamine B solution by single-liquid electrospray.

[0029] Figure 9b This is the mass spectrum of reserpine solution by single-pass electrospray.

[0030] Fig.9c This is a mass spectrum of the rhodamine B and reserpine solutions simultaneously electrosprayed by dual liquid paths according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a multi-channel electrospray microfluidic chip and its application. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] During mass spectrometry analysis, the extraction and ionization effects of the liquid to be tested have a great influence on the test results of the mass spectrometry. However, since the relative positions of the two independent nozzles of the macroscopic electrospray extraction ionization (EESI) device are not fixed, the relative positions of the two independent nozzles need to be adjusted before the experiment. Such operations often reduce the operability and reproducibility of the experiment. In addition, the extraction efficiency of liquid electrospray extraction using the EESI device is not high, which can easily lead to low mass spectrometry test signals and affect the test results.

[0033] A preferred embodiment of a multi-channel electrospray microfluidic chip provided by the present invention is shown in 1 and Figure 2 The multi-channel electrospray microfluidic chip comprises: two first gas phase flow channels 10 and at least two liquid phase flow channels 20; the liquid phase flow channels 20 are arranged between the two first gas phase flow channels 10; the nozzles of the first gas phase flow channels 10 and the nozzles of the liquid phase flow channels 20 are arranged at intervals.

[0034] The present invention can be used for the extraction electrospray ionization of complex test liquids, which refer to complex liquids with multiple components that have not been extracted, such as urine containing test substances. Figure 5 In the process of using the microfluidic chip, the liquid phase flow channel 20 is used to guide the liquid, wherein at least one liquid phase flow channel 20 is used to guide the liquid to be tested, and the remaining liquid phase flow channels 20 are used to guide the extract, and only a high voltage needs to be applied to the extract. Since the intervals of the liquid phase flow channels 20 are small, during the extraction electrospray process, the liquid to be tested and the extract can be mixed at the nozzle of the liquid phase flow channel 20, so that the extract can extract and ionize the liquid to be tested, and form a mixed Taylor cone spray, and atomize at the same time. Due to the high integration of the microfluidic chip, the relative position of the test liquid flow channel and the extract liquid flow channel is fixed and the nozzle interval is small, so that the spray conditions of the two liquids are stable and consistent, and the atomization effect is good. Preferably, the liquid phase flow channel 20 located in the middle is used to guide the liquid to be tested, so that a Taylor cone spray form in which the extract and the liquid to be tested are mixed can be formed at the nozzle of the liquid phase flow channel 20, so that the two liquids are evenly mixed, and the extraction efficiency and extraction effect of the extract on the liquid to be tested are further improved, and the subsequent test signal is enhanced. The first gas phase flow channel 10 is used to guide the gas. The first gas phase flow channel 10 is distributed on both sides of the liquid phase flow channel 20, which can prevent the mixed liquid from spreading to both sides at the nozzle of the liquid phase flow channel 20 and affecting the spray effect. At the same time, the mixed liquid can be further atomized to improve the ionization efficiency. The setting of the first interval can obtain a mixed Taylor cone of appropriate size, thereby further improving the spray effect of the microfluidic chip. The present invention effectively realizes the detection of complex test liquids, reduces the pre-treatment process of the test liquids, improves the extraction efficiency of complex test liquids, and enhances the ionization ability of the test liquids.

[0035] In one embodiment, the nozzles of two adjacent liquid phase flow channels 20 are spaced apart. Preferably, the width of the nozzle spacing of the liquid phase flow channel 20 is 20 μm. A smaller spacing is helpful for mixing the test liquid and the extraction liquid.

[0036] In another embodiment, at least one second gas-phase flow channel 30 is further included, which is located between the at least two liquid-phase flow channels 20, that is, the second gas-phase flow channel 30 is used to separate the liquid-phase flow channels 20, and the nozzle of the second gas-phase flow channel 30 is spaced apart from the nozzle of the liquid-phase flow channel 20, so that a structure in which multiple independent nozzles are arranged side by side can be formed. An independent nozzle refers to a nozzle composed of at least one liquid-phase flow channel 20 arranged between two gas-phase flow channels (including the first gas-phase flow channel 10 and / or the second gas-phase flow channel 30). For example, two first gas-phase flow channels 10, three liquid-phase flow channels 20 and one second gas-phase flow channel 30 can be used, wherein the second gas-phase flow channel 30 is arranged between any pair of adjacent liquid-phase flow channels 20, thereby forming two independent nozzles, wherein one independent nozzle has nozzles of two liquid-phase flow channels 20, and the other independent nozzle has only one nozzle of a liquid-phase flow channel 20; it can also be arranged as follows Figure 4 The structure adopts two first gas phase flow channels 10, three liquid phase flow channels 20 and two second gas phase flow channels 30, wherein the two second gas phase flow channels 30 are arranged between adjacent liquid phase flow channels 20 to form three independent nozzles each having only one liquid phase flow channel 20 as the nozzle.

[0037] In a preferred embodiment, see Figure 3 and Figure 4 The second gas phase flow channel 30 separates the adjacent liquid phase flow channels 20, forming a structure in which the second gas phase flow channel 30 and the liquid phase flow channel 20 are arranged alternately, that is, the liquid phase flow 20 in the independent nozzle formed has only one nozzle. In this way, during the extraction electrospray process, multiple independent nozzles form multiple smaller separated Taylor cone sprays, such as Figure 6As shown. In the process of electrospray extraction of complex liquid to be tested, voltage is also applied only to the extract, and the test liquid and the extract form separate Taylor cone sprays at the nozzles of the liquid phase flow channel 20 where they are located, and are atomized separately. In the atomized state, the extract droplets and the test liquid droplets collide with each other, thereby realizing the extraction and ionization of the test liquid by the extract. It should be noted that the flow channels of the extract and the test liquid can be selected according to needs and spray effects. Such a setting can also be used for dual-liquid path or multi-liquid path electrospray ionization. Generally speaking, dual-path or multi-path electrospray ionization can reduce the ion suppression effect, thereby accurately determining the mass number through the internal standard, enhancing the mass spectrometry signal intensity, improving the sensitivity, and realizing high-efficiency and high-throughput analysis of macromolecular samples. However, when two nozzles are electrosprayed at the same time, due to the strong electric field interference between the nozzle tips, it is usually difficult to achieve simultaneous electrospray of dual-path or multi-path nozzles. Since the present invention sets a gas phase flow channel between adjacent liquid phase flow channels 20, the liquid phase flow channels 20 are all independent of each other, and there is almost no general nozzle tip shape, so the electric field interference between each other is very small, and the simultaneous electrospraying of dual-channel or multi-channel nozzles can be realized, and the spraying stability is relatively high. It should be noted that when performing dual liquid path or multi-liquid path electrospraying, since the test liquid is not extracted during the spraying process, it is necessary to extract or purify the test liquid in advance and then perform electrospraying. When performing dual liquid path or multi-liquid path electrospraying, the liquid phase flow channels 20 are all used to guide the test liquid, and high voltage is applied to the test liquid for electrospraying, wherein the test liquids may be the same or different, and simultaneous electrospraying of different test liquids can simultaneously obtain mass spectra of different test objects, thereby improving the detection efficiency.

[0038] The multi-channel electrospray ionization microfluidic chip of the present invention further expands the scope of the combination of microfluidic chips and mass spectrometers, and can be widely used in many aspects such as rapid mixing reactions of substances, protein folding and stretching analysis, and internal standard testing. It is truly beneficial to achieve rapid detection of complex samples, get rid of the cumbersome sample pretreatment process in the laboratory, and make a certain contribution to the development of miniaturization and portability of mass spectrometers.

[0039] See also Figures 1 to 4 , each liquid phase flow channel 20 is provided with a liquid phase inlet 21 at the other end, and the liquid phase inlets 21 of different liquid phase flow channels 20 are different, and the liquid enters the liquid phase flow channel 20 from the liquid phase inlet 21, and forms a Taylor cone spray at the nozzle of the liquid phase flow channel 20. The other end of the two first gas phase flow channels 10 and the other end of the second gas phase flow channel 30 converge to form a gas phase dry flow channel 40, and the end of the gas phase dry flow channel 40 is provided with a gas phase inlet 41, that is, the two first gas phase flow channels 10 and all the second gas phase flow channels 30 share a gas phase inlet 41, and the gas enters the gas dry flow channel 40 from the gas phase inlet 41 and passes through each first gas phase flow channel 10 and the second gas phase flow channel 30 separately at the setting position.

[0040] In one embodiment, the interval between the nozzle of the first gas phase flow channel 10 and the nozzle of the liquid phase flow channel 20 and the interval between the nozzle of the second gas phase flow channel 30 and the nozzle of the liquid phase flow channel 20 are both 10-100 μm, preferably, the interval is 15-25 μm. There needs to be a certain interval between the outlet of the liquid phase flow channel 20 and the nozzle of the gas phase flow channel (including the first gas phase flow channel 10 or the second gas phase flow channel 30) to form a Taylor cone spray of suitable size. A larger interval results in a larger Taylor cone, unstable spray, and affects the spray effect; a smaller interval is easy to cause the gas phase flow channel and the liquid phase flow channel to mix during the preparation of the chip due to the loose bonding of the upper and lower halves.

[0041] In one embodiment, the central axes of the nozzles of the liquid phase flow channel 20, the first gas phase flow channel 10 and the second gas phase flow channel 30 are parallel, and the nozzles are all on the same plane. In other words, a section of all flow channels close to the nozzles are distributed in parallel with each other, and the gas phase and the liquid phase are ejected simultaneously. The parallel distribution can make the first gas phase flow channel 10 and the second gas phase flow channel 30 on both sides of each liquid phase flow channel 20 or all liquid phase flow channels 20 completely symmetrically distributed, so that the liquid can be ejected completely in parallel and at the same time. When the liquid phase nozzle is facing the mass spectrometer inlet, the parallel ejected liquid can enter the mass spectrometer as much as possible and more accurately, ensuring that the signal will not be reduced due to the detection signal caused by inaccurate spray direction.

[0042] In one embodiment, the depth of the first gas phase flow channel 10 and the second gas phase flow channel 30 is greater than the depth of the liquid phase flow channel 20. The first gas phase flow channel 10 and the second gas phase flow channel 30 are deeper, which helps to atomize the liquid and prevent the liquid at the nozzle of the liquid phase flow channel 20 from spreading.

[0043] In one embodiment, the multi-channel electrospray microfluidic chip is made of PDMS or PMMA. The present invention uses a multi-layer overlay soft lithography method to process the microfluidic chip, and polydimethylsiloxane (PDMS) or polymethylmethacrylate (PMMA) is used as the processing material. The soft lithography process of the multi-channel electrospray microfluidic chip mainly includes the processes of glue throwing, exposure, development, mold entering, curing, mold removal, cutting, punching, bonding, etc. The process is very mature and the present invention does not repeat it. Specifically, the upper and lower halves of the microfluidic chip can be formed separately, and the upper and lower halves both have a microchannel structure. Therefore, the upper and lower halves are combined and processed into a complete chip by bonding PDMS to PDMS. According to the different application requirements of the microfluidic chip, the processing technology will vary. This method has the advantages of simple processing technology, easy bonding, low cost, and convenience for large-scale preparation.

[0044] The present invention also provides an application of a multi-channel electrospray microfluidic chip, wherein the multi-channel electrospray extraction microfluidic chip is mainly used for liquid extraction electrospray or for simultaneous electrospray of multiple liquid paths to generate tiny atomized droplets for detection by a mass spectrometer.

[0045] like Figure 7a and Figure 7b As shown in the figure, the signal intensity and signal-to-noise ratio of rhodamine obtained by using the EESI ion source are much lower than the signal intensity and signal-to-noise ratio tested by the microfluidic chip ion source. The total ion current (mass-to-charge ratio 443-444) signal intensity of the rhodamine solution (3 μM) tested using the EESI ion source. Figure 8 As shown in the figure, it can be seen that the relative standard deviation (RSD) of the total ion current intensity of the two samples in the dual-path electrospray process is only 1.6%, which fully proves the stability of this dual-path simultaneous electrospray. Figure 9a , Figure 9b and Fig.9c As shown in the figure, when two single-channel sprays were performed respectively, the average signal intensities of rhodamine and reserpine were 1.1×10 5 and 4.8×10 5 However, keeping the conditions unchanged, adding two samples to the two channels of the microfluidic chip at the same time and applying high voltage, and spraying them independently at the same time, the signal intensity of rhodamine was almost unaffected, while the signal intensity of reserpine was slightly reduced. This shows that when spraying at the same time, the simultaneous electrospray of the two channels will have a certain impact, including electric field intensity interference and ion suppression, but the overall impact is small and basically will not affect the mass spectrometry signal test.

[0046] In summary, the present invention provides a multi-channel electrospray microfluidic chip, which includes two first gas phase flow channels and at least two liquid phase flow channels, wherein the liquid phase flow channels are arranged between the two first gas phase flow channels; the nozzle of the first gas phase flow channel is arranged at intervals from the nozzle of the liquid phase flow channel. In the process of electrospraying, the present invention can realize the extraction function of macroscopic electrospraying because the relative position of the liquid phase nozzle and the first gas phase nozzle is fixed, and the spraying conditions are stable and consistent. On the one hand, it can improve the extraction efficiency and extraction effect of the extracting liquid on the test liquid, which is conducive to the rapid detection of complex samples; on the other hand, it solves the problem that it is difficult to electrospray two or more liquid paths at the same time, and finally creates more application forms for the combination of microfluidic chips and mass spectrometers, which can be widely used in many aspects such as rapid mixing reaction of substances, protein folding and stretching analysis, and internal standard testing.

[0047] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A multi-channel electrospray microfluidic chip, characterized in that: include: Two first gas phase flow channels, at least two liquid phase flow channels and at least one second gas phase flow channel; the liquid phase flow channels are arranged between the two first gas phase flow channels; the second gas phase flow channel is arranged between the at least two liquid phase flow channels, and the interval between the nozzle of the first gas phase flow channel and the nozzle of the liquid phase flow channel and the interval between the nozzle of the second gas phase flow channel and the nozzle of the liquid phase flow channel are both 10-100 μm; Central axes of the nozzle of the liquid phase flow channel, the nozzle of the first gas phase flow channel, and the nozzle of the second gas phase flow channel are parallel and on the same plane.

2. The multi-channel electrospray microfluidic chip according to claim 1, characterized in that: The other end of each of the liquid phase flow channels is provided with a liquid phase inlet.

3. The multi-channel electrospray microfluidic chip according to claim 1, characterized in that: The two first gas phase flow channels and the other end of the second gas phase flow channel converge to form a gas phase dry flow channel, and a gas phase inlet is arranged at the end of the gas phase dry flow channel.

4. The multi-channel electrospray microfluidic chip according to claim 1, characterized in that: The depths of the first gas-phase flow channel and the second gas-phase flow channel are greater than the depth of the liquid-phase flow channel.

5. The multi-channel electrospray microfluidic chip according to any one of claims 1 to 4, characterized in that: The multi-channel electrospray microfluidic chip is made of PDMS or PMMA.

6. An application of the multi-channel electrospray microfluidic chip as claimed in claim 5, characterized in that: The multi-channel electrospray extraction microfluidic chip is used for liquid extraction electrospray or for simultaneous electrospray of multiple liquid channels.

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