COMBINED DEVICE FOR LIQUID-PHASE MASS SPECTROMETRY SAMPLING AND ELECTROSPRAY

Abstract

The present disclosure is applicable to the field of analytical instruments, and provides a multifunctional probe for sample pickup, delivery and electrospray ionization used for direct sample analysis with a liquid-phase mass spectrometer. The multifunctional probe comprises a needle body and a tip part, wherein said tip part is continuously contracted from the needle body in whole or in part, and said tip part is provided with a solution carrying structure. The present disclosure further provides a combined sample introduction and electrospray device for liquid-phase mass spectrometry comprising said multifunctional probe, further comprising a mechanical arm and an ion source with a sealed chamber and a needle port on the sealed chamber.

Claims

1. A multifunctional probe for sample pickup, delivery and electrospray ionization for liquid-phase mass spectrometric analysis, comprising a needle body and a tip part, wherein said tip part is continuously contracted from the needle body in whole or in part, said tip part is provided with a solution carrying structure which comprises one or more liquid-retaining grooves, and an end of the one or more grooves coincides with an end of said tip part.

2. The multifunctional probe of claim 1, wherein each of the one or more grooves has a cross section of substantially V-shaped, U-shaped or Ω-shaped.

3. The multifunctional probe of claim 1, wherein an outer surface of said tip part and an inner surface of the one or more grooves are simultaneously provided with a non-stick layer of no more than 50 μm in thickness.

4. The multifunctional probe of claim 1, wherein a part or all of said tip part is made of conductive material, and when a part of said tip part is made of conductive material, a device for connecting spray voltage is provided outside in connection with said tip part.

5. The multifunctional probe of claim 1, wherein said multifunctional probe is configured for mass spectrometric analysis of blood samples, said tip part has an oblique cut edge with a polar adsorption material filled therein.

6. The multifunctional probe of claim 5, wherein the polar adsorption material is a plant fiber with enhanced polarity by chemical modification, silica gel particles with polar groups bonded on surface, a nanomaterial with incompletely carbonization and bonded polar groups, or a combination thereof.

7. A combined sample introduction and electrospray device for liquid-phase mass spectrometry, comprising the multifunctional probe of claim 1, and further comprising an ion source sealed chamber, wherein the ion source sealed chamber is hermetically coupled with and relatively fixed on a mass spectrometer inlet, the ion source sealed chamber comprises a needle port, and the needle port has a needle inlet for inserting said multifunctional probe.

8. The device of claim 7, wherein the combined device further comprises a sample-injecting mechanical arm to perform automatic operation.

9. The device of claim 7, wherein the position of the needle port on the ion source sealed chamber is set in such a way that after said multifunctional probe penetrates the needle port, the tip of said multifunctional probe is aligned with the mass spectrometer inlet and is 2-20 mm away from the mass spectrometer inlet.

10. A sample introduction method for liquid-phase mass spectrometric analysis, comprising: S1, sampling with the multifunctional probe of claim 1; S2, inserting the multifunctional probe into the ion source sealed chamber, wherein a tip of said multifunctional probe is aligned with the mass spectrometer inlet, and is sprayed under high voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is an overall schematic diagram of a combined device for direct sample introduction and ionization of liquid-phase mass spectrometry according to an embodiment of the present disclosure.

[0029] FIG. 2a, FIG. 2b and FIG. 2c are schematic diagrams of a multifunctional probe according to an embodiment of the present disclosure, wherein said tip part has a channel.

[0030] FIG. 3 is a schematic diagram of a multifunctional probe with a plurality of parallel grooves engraved on the surface of the needle according to an embodiment of the present disclosure.

[0031] FIG. 4 is a schematic diagram of a multifunctional probe with a threaded channel engraved on the surface of the needle according to an embodiment of the present disclosure.

[0032] FIG. 5 is a schematic diagram of a multifunctional probe with capillary according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make clearly elaborate the technical problems to be solved, the technical schemes, and the beneficial effects by the present disclosure, the present disclosure will be further explained in detail in reference to the drawings and embodiments. It should be appreciated that the specific embodiments described herein are only for elucidating rather than limiting the present disclosure.

[0034] As shown in FIG. 1, the present disclosure provides a combined device of direct sample-introduction and ionization for liquid-phase mass spectrometric analysis. Said combined device comprises a mechanical arm 1, a sample holder 2, an injecting needle port 3, a high-voltage connector 4, a multifunctional probe for sample pickup and delivery 5, an ion source sealed chamber 6 and a mass spectrometer inlet 7, wherein the sample tray is configured for storing unknown or standard samples to be tested. The needle port 3 is located at the end (moving end) of the sample-injecting mechanical arm 1. The relative location of said needle port near the farthest end of motion of said mechanical arm 1. The high-voltage connector 4 and said multifunctional probe 5 are connected with the needle port 3. The ion source sealed chamber 6 and the mass spectrometer inlet 7 are provided on the mass spectrometer (not shown in the figure). Said multifunctional probe 5 can be inserted into the ion source sealed chamber 6 to perform electrospray ionization on the sample for mass spectrometric detection. In the specific operation process, the needle port 3 and the ion source sealed chamber 6 are fixed with respect to the mass spectrometer, and the mechanical arm 1 drives said multifunctional probe 5 to complete the motion cycle of sample pickup, and delivery.

[0035] The proportion shown in the drawings in the present disclosure is only for schematic purposes, and is not used for limiting the dimensions of the related components.

[0036] The present disclosure provides a device for direct sample introduction and ionization in liquid-phase mass spectrometry. Said device comprises a multifunctional probe that picks up the sample, delivers it to the ion source of the mass spectrometer, and sprays the sample under high voltage to ionize the analytes in the sample. Said multifunctional probe operates in acupuncture style. Sample analysis with said multifunctional probe is quick and simple resulting in significant efficiency enhancement for liquid-phase mass spectrometry.

[0037] Specifically, as shown in FIGS. 2a-2c and FIGS. 3-5, said multifunctional probe 5 comprises a needle body 51 and a tip part 52, wherein said tip part is continuously and smoothly contracted from the needle body in whole or in part. There is only one tip for each multifunctional probe. Said multifunctional probe 5 can be used as a disposable item to be discarded or recycled after use. In this case, carry-over or needle washing would be completely avoided. In other embodiments, said multifunctional probe 5 can be repeatedly used by a quick plasma washing.

[0038] Specifically, said multifunctional probe 5 may be made of metal, ceramic, quartz and glass with high strength, good chemical stability, good rigidity, low brittleness, and high-strength alloy. Materials such as stainless steel, tungsten steel and high-carbon steel are preferred. If said multifunctional probe 5 is made of an insulating material, a conductive means needs to be arranged in the channel on the needle, and the conductive structure converges into a conductive point or a conductive ring on the surface of the needle above the channel, so as to provide high voltage connection to the tip of said multifunctional probe or the sample solution on the probe to ensure electrospray. The needle body can be a solid structure, preferably a columnar structure. A columnar structure makes installation of said multifunctional probe 5 easier than many other structures. Said tip part is provided with a solution carrying structure, which can carry the sample solution by capillary effect without dripping or quickly evaporating during sample delivery. The volume of the liquid sample carried by said tip part is much smaller than an ordinary sample injection volume. Specifically, the solution carrying mechanism is structured to have one or more liquid-retaining grooves. The end of every liquid-retaining groove merges at the end point of said tip part. Said liquid-retaining grooves each has a length of 10 to 35 mm on a needle with diameter 0.2 to 3 mm, preferably 0.4 to 1.7 mm. The length, depth and shape of said liquid-retaining grooves may be arbitrarily selected according to the operation or installation requirements. However, the width of said liquid-retaining grooves should not exceed the radius of the needle, preferably 0.1 mm to the radius of the needle. The depth of said liquid-retaining grooves is from 0.1 mm to cutting-through the needle body. The shape of longitudinal direction of said liquid-retaining grooves is straight, curved, or spiral around the needle. The cross section of said liquid-retaining grooves can be V-shaped, U-shaped, Ω-shaped or in any other shape. The diameter of said multifunctional probe is preferably 0.5 to 1.5 mm. The tip part of said multifunctional probe is about 3 to 3.5 mm in length at the tip part (including the inner surface of the channel) is preferably smooth and non-sticky (no absorption). A layer of no more than 50 μm in thickness may be generated by surface treatment cover the specific surface. For example, such a non-stick layer may be Teflon coating or other coating materials. Common surface treatment processes such as plasma spraying, electropolishing, electroplating, coating, etc. may be employed to form a dense thin layer of metal oxide, epoxy resin, polytetrafluoroethylene, or graphene on the surface of the needle tip part. In addition, the liquid-retaining grooves of said multifunctional probe 5 may be filled or coated with a kind of adsorption material, such as silica gel, fiber, activated carbon, bentonite, or a strong polar filler made from chemical modification of the aforementioned materials. The purpose of filling said liquid-retaining grooves with special adsorption materials is to achieve the effect of in-mobilizing matrix species in a particular sample and letting analyte undergoing electrospray free of interference from the matrix. This would make sample processing seamless and effortless for the analyst. In a specific embodiment, the needle tip is a hollow with a long-beveled opening, the length of the needle is about 1 to 5 mm. The needle body is above the bevel opening, and the top end is further provided with an abutting structure such as an injecting needle connecting sleeve (Luer connector), a magnetic rod, a magnetic attraction rod, a connector with a bayonet or any device that can be easily grabbed or abutted manually or by the mechanical arm of an automatic sample injector.

[0039] FIGS. 2a-2c show an embodiment of a multifunctional probe according to the present disclosure. Said multifunctional probe provided by this embodiment is a metal solid needle, and said tip part of the needle has only one channel, which is located at the center said tip part of said multifunctional probe. The needle tip is an oblique cut, shaped like a medicine spoon for laboratory use. The cross section of the channel is Ω-shaped, with a length of 3 to 10 mm. The total length of the needle is 50 to 150 mm, the needle tip is 25 to 50 mm for sample-injecting and spraying, the diameter is 0.4 to 1 mm, and the diameter of the needle body is 1.5 to 3 mm. According to the size of the channel on the needle tip, the amount of the sample solution dipped by said multifunctional probe should not exceed 5 μL each time, preferably 0.5 to 2 μL.

[0040] FIG. 3 shows another embodiment of a multifunctional probe according to the present disclosure. Said multifunctional probe provided by this embodiment is a solid metal needle with a plurality of parallel liquid-retaining grooves on the surface, and the grooves are located at the periphery of said tip part of said multifunctional probe. The diameter of the needle body is 0.3 to 2 mm, the length of the whole needle is 30 to 35 mm, and the contracted length of the tip is 3 to 10 mm. The grooves are straight lines or “S” lines converging to the tip. Each said liquid-retaining groove has a length of 3 to 20 mm and a depth of 0.1 to 1 mm. The number of channels is unlimited, and the surface of the tip part of the multifunctional probe can be fully engraved at most.

[0041] FIG. 4 shows another embodiment of a multifunctional probe according to the present disclosure. Said multifunctional probe provided by this embodiment is a metal needle with a groove engraved on the periphery of its tip part. The diameter of the needle body is 0.3 to 2 mm, the length of the whole needle is 30 to 35 mm, and the length of contracted portion until the tip is 3 to 10 mm. There may be one or more liquid-retaining grooves. The grooves can be spiral around the tip part of said multifunctional probe from 3 to 20 mm above the needle tip down to the very end of its tip. The depth of each groove needs to be at least ˜0.1 mm. Above the tip the groove can be as deep as penetrating through the needle.

[0042] FIG. 5 shows another embodiment of a multifunctional probe according to the present disclosure. Said multifunctional probe provided by this embodiment is used for direct mass spectrometric analysis of blood samples. When measuring the concentration of blood samples, a multifunctional probe is made by a capillary tube with one end obliquely cut into beveled tip. The capillary tube and the beveled tip is filled with highly polar adsorption materials, for example, plant fibers, chemically modified fibers polarity enhanced characteristics, silica gel particles with polar groups bonded on the surface, or nanomaterials with incomplete carbonization or bonded polar groups, and so on. These materials have strong adsorption on blood matrix species with high polarity and/or high water-solubility, but have weak adsorption on most drug molecules. When said multifunctional probe dips into the blood sample, the matrix species in the blood sample are adsorbed on the adsorption materials while small drug molecules remaining in the liquid portion of the sample picked up by said multifunctional probe. During electrospray, the strongly adsorbed species does not flow to the needle tip of said multifunctional probe to spray, only the liquid in the blood sample undergoes spraying, so therefore matrix effect does not occur. In this embodiment, anticoagulants may be added to the blood samples. One to three folds volume of water may also be added to lower the viscosity of blood samples. Another precaution step for alleviate matrix effect is to precipitate proteins in the blood sample by adding precipitants such as methanol, acetonitrile, perchloric acid, etc., then sampling the supernatant by said multifunctional probe for testing. To ensure secured filling, the absorption materials may mix with 0.1% to 3% adhesives to glue in the grooves of said multifunctional probe. After dry, the adhesives used for gluing must be insoluble in sample solvent such as water, methanol, and acetonitrile.

[0043] The above multifunctional probe 5 is installed onto the free moving end of the mechanical arm 1. The mechanical arm 1 slides on the spline shaft to move said multifunctional probe 5 to accomplish its sample handling cycle from sample pickup to sample ionization, as shown in FIG. 1. The movement range of the mechanical arm must at least cover all the sample locations on the sample tray 2 and the needle port 3 on the ion source of the mass spectrometer, so as to realize the automatic operation of sampling and sample-injecting. The top of the needle port 3 is a funnel-shaped to ensure needle insertion smoother. The needle port 3 is fixed on the outer shell of the ion source sealed chamber 6 with a hole in the center to allow said multifunctional probe 5 to enter and exit the sealed chamber freely. The specific fixing method needs to ensure that the needle tip can be aligned with the mass spectrometer inlet 7 after the multifunctional probe 5 penetrates through the needle base. The distance from the mass spectrometer inlet 7 is 2 to 20 mm, and preferably the included angle with the centerline of the mass spectrometer inlet 7 is 0 to 90 degrees.

[0044] In the specific embodiment, the automatic sample injector is matched with the mass spectrometer, and the position with respect to the mass spectrometer is fixed.

[0045] Specifically, the ion source sealed chamber 6 is hermetically abutted and relatively fixed with the mass spectrometer inlet 7, and isolated from the external environment. The inside of the ion source sealed chamber is in vacuum communication with the inside of the mass spectrometer through the mass spectrometer inlet 7. The internal volume of the ion source sealed chamber 6 can at least accommodate the ellipsoidal atomization cloud formed by spraying from the tip of said multifunctional probe 5 therein, in which the major axis is 5 to 30 mm and the minor axis is 5 to 20 mm. The needle port 3 further comprises a high-voltage connector 4 provided at the inner side of the needle inlet, which is used to apply high voltage of 1 to 7 kV to the sample solution on said multifunctional probe 5. The high-voltage connector 4 can be any conductive connector that can be in stable contact with the conductive part of said multifunctional probe 5. Said conductive contactor can be made by an elastic metal piece, a hole with an inner diameter equal the outer diameter of the conductive part of said multifunctional probe 5, a conductive ring with conductive tentacles in its inner side to ensure electric connection to said multifunctional probe, and so on. One end of a high-voltage transmission wire is connected with the high-voltage connector 4, and the other end thereof is connected with a spray voltage power supply of the mass spectrometer. For safety, the exposed part of said high-voltage connector 4 is wrapped by an insulator or hidden in a structure inaccessible to human hands.

[0046] The embodiment of the present disclosure further provides an integrated system comprising the above combined device for direct sample introduction and ionization for liquid-phase mass spectrometry.

[0047] The operation of the integrated sample introduction and ionization system for liquid-phase mass spectrometry provided by the embodiment of the present disclosure comprises a sequence of actions driven by the mechanical arm 1. The sequence of mechanical arm actions starts from moving said multifunctional probe 5 to the designated sample vial in the sample tray 2, punching it through the sealing pad at the top of the sample vial, immersing the liquid-retaining grooves on its tip part in the sample solution for 1 to 2 seconds to completely fill the grooves, then pulling it out from the sample solution, and finally moving it into the ion source sealed chamber through the needle port to an optimized position for electrospray. When said multifunctional probe is pulled out from the sample vial, the sealing pad of the sample vial only wipes the solution on the surface of the probe without eliminating the solution inside the liquid-retaining grooves. Capillary effect of the grooves can prevent sample solution in the grooves not only from being wiped by the sample vial seal pad but also from dripping or quick evaporating during transportation to the sealed chamber. The optimized position of said multifunctional probe inside the sealed chamber is positioned with its tip aligned with the mass spectrometer inlet 7 and 2 to 20 mm away from the inlet at an angle of 0 to 90 degrees facing the inlet. At this optimized position, said multifunctional probe 5 acts as an electrospray needle. The high voltage of 1-7 kV is then applied to the tip of said multifunctional probe to facilitate electrospray ionization on the carried sample solution in the liquid-retaining grooves. The ion collection potential at the mass spectrometer inlet and the vacuum suction inside the mass spectrometer drive the ions generated from the electrospray into the mass spectrometer for detection. The ion collection efficiency could reach 100% when the sealed chamber is under vacuum condition and the inlet of the mass spectrometer is an open pathway.

[0048] The embodiment of the present disclosure further provides an integrated operation method of sample introduction and ionization of liquid-phase mass spectrometry, which is implemented by the above system.

[0049] The integrated sample introduction and ionization system for liquid-phase mass spectrometry according to the present disclosure has the following advantages: (1) the needle has multifunction for sample pickup, sample delivery, and electrospray ionization; (2) the atomization efficiency is extremely high resulting in droplets less than 1 μm in diameter; (3) the resulted mass spectrometric signal has been repeatedly tested to have a relative standard deviation less than 15%, which meets the requirements for mass spectrometric quantification; (4) matrix effect is significantly reduced based on the fact that a pure standard solution and a picked blood sample of the same concentration in its supernatant after protein precipitation result in similar signal strength; (5) said multifunctional probe delivers sample directly to analysis without resorting to any pump or injection valve, needs only very small amount of sample (0.1-10 μL) for each analysis, and can be very quickly cleaned for residue removal; (6) no sheath gas nor mobile phase solution is needed for sample analysis; (7) the sensitivity is 2 to 100 times higher than that of LC/MS; (8) the problems caused by using the liquid chromatography for sample input to the liquid-phase mass spectrometer are completely eliminated, so that mass spectrometric analysis becomes faster, and simpler, and more reliable; (9) the throughput of sample analysis becomes 5 to 50 times higher than that of an LC/MS system; (10) the hardware cost is more than 20% lower than that of an LC/MS, and the sample analysis cost is reduce more than 80% compare with LC/MS.

[0050] The above is only a preferred embodiment of the present disclosure, and it is not intended to limit the present disclosure. Any modifications, equivalent substitutions, and improvements made within the principles of the present disclosure should be included in the scope of protection of the present disclosure.