A sampling device and sampling method for nanoliter liquid chromatograph

Abstract

The present invention discloses an injection device and injection method for a nanoliter liquid chromatograph, including: an injection needle, a small plunger, a large plunger, a sealing gasket, a tight hoop, a low-pressure body, a high-pressure body, a support ring, a cover plate, and a system flow path interface. The large plunger in the nanoliter liquid chromatograph automatic injection device drives the small plunger to move upward to extract a quantitative sample. The mobile phase is driven to move by a driving pump, so that the mobile phase flows through the gap between the injection needle and the small plunger, and drives the sample to move toward the chromatographic column through the injection needle seat. Since the inner diameter of the injection needle is extremely small and the material of the small plunger is incompressible, the present invention can realize nanoliter micro-injection of any volume with almost no loss, and can realize accurate injection of tens of picoliters of samples at the minimum. The present invention is convenient for cleaning the inner and outer walls of the injection needle after sample extraction through flow path design, so that the residue is as small as possible, and the cross contamination rate is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of liquid treatment, and in particular to a sampling device and a sampling method for a nanoliter liquid chromatograph. Background Art

[0002] The autosampler is an important part of the nano-liquid chromatograph. The nano-liquid chromatograph autosampler extracts the sample from the sample bottle or sample tube containing the analysis object and injects it into the analytical flow path of the nano-liquid chromatograph for analysis. The analytical flow path is usually under high pressure of 10MPa to 120MPa. The sample transitions from normal pressure to the high-pressure flow path, which is usually achieved by a high-pressure six-way valve. The autosampler can continuously supply samples in multiple sample bottles to the nano-liquid chromatograph for qualitative and quantitative analysis. After the sample is injected into the analytical flow path through the injector, the remaining part of the sample will remain in the injection needle and the loading flow path. The sample adsorbed on the needle or on the wall of the flow path may be mixed with the sample to be analyzed into the analytical flow path in the next injection, affecting the analysis results of the chromatography. The autosampler requires the residue to be as small as possible. The cross-contamination rate is a parameter that quantifies the size of the residue. The smaller the cross-contamination rate, the better the injector performance. The solution to the residue is to clean the injection needle and the loading flow path after the sample is extracted.

[0003] A problem with nanoliter liquid chromatography injectors is that it is difficult to achieve nanoliter micro-injection of any volume without loss. An existing nanoliter liquid chromatography autosampler uses an injection needle to draw samples and controls the sampling volume through a metering pump, which can only ensure a minimum injection volume of about 0.1 μL. Another method for achieving nanoliter sample injection is to integrate a nanoliter quantitative loop on a six-way valve rotor, such as Figure 1 As shown in the figure, an excess amount of sample is sucked in during injection, and the sample in the quantitative loop is switched to the high-pressure analysis flow path through a six-way valve. This method can only achieve nanoliter fixed volume injection, and the injection volume cannot be changed. In addition, the sample outside the quantitative loop cannot enter the analysis system, resulting in a waste of precious samples (such as biological samples). Summary of the invention

[0004] In order to solve the deficiencies in the above-mentioned prior art, the object of the present invention is to provide an injection device and an injection method for a nanoliter liquid chromatograph, which can realize nanoliter micro-injection of any volume without loss, and can achieve precise injection of samples of at least tens of picoliters.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a sample injection device for a nanoliter liquid chromatograph, comprising a sample injection needle, a small plunger, a large plunger, a high pressure body, and a system flow path interface;

[0006] A cavity for accommodating a large plunger is provided in the high-pressure body, the injection needle is connected to one end of the high-pressure body and communicates with the cavity, the large plunger is slidably connected in the cavity, and the small plunger is fixedly installed at the end of the large plunger, and the diameter of the small plunger is smaller than the inner diameter of the injection needle, so that the small plunger and the inner cavity clearance of the injection needle are matched;

[0007] The system flow path interface is arranged at one end of the high-pressure body, and a straight channel connecting the system flow path interface and the cavity is arranged in the high-pressure body; the bottom of the high-pressure body has a first surface and a second surface, the first surface and the second surface are both planes, and the injection needle is connected to the first surface, the system flow path interface is arranged on the second surface, the straight channel is perpendicular to the second surface, and there is an obtuse angle between the second surface and the first surface.

[0008] Optionally, the top of the high-pressure body is connected to a low-pressure body, a support ring is connected between the top of the low-pressure body and the large plunger, and the support ring is slidably matched with the large plunger.

[0009] Optionally, a sealing gasket is connected between the high-pressure body and the large plunger, and a dynamic seal is formed between the sealing gasket and the large plunger, and the sealing gasket is tightened by a tightening hoop.

[0010] Optionally, a tapered portion is provided at one end of the cavity close to the injection needle, and a chamfer is provided at the top end of the injection needle.

[0011] According to the above-mentioned sample injection device of nano-liquid chromatograph, the present invention also proposes a sample injection method of nano-liquid chromatograph, comprising the following steps:

[0012] The injection device of the nano-liquid chromatograph is switched to the low-pressure zone through a high-pressure six-way valve, and the injection needle is connected to the sample bottle;

[0013] A large plunger in the sample injection device of the nano-liquid chromatograph drives a small plunger to move upward to extract a quantitative sample;

[0014] The injection needle is inserted into the injection needle seat;

[0015] The sampling device of the nanoliter liquid chromatograph is switched to the high pressure zone through the high pressure six-way valve, the sampling device of the nanoliter liquid chromatograph is connected to the driving pump of the nanoliter liquid chromatograph, and the sampling needle is connected to the sampling needle seat;

[0016] High-pressure liquid enters the sampling device of the nano-liquid chromatograph from the system flow interface, driving the sample from the injection needle into the injection needle seat;

[0017] The mobile phase is driven by the driving pump to flow through the gap between the injection needle and the small plunger, driving the sample to move toward the chromatographic column through the injection needle seat.

[0018] Optionally, when the injection device of the nanoliter liquid chromatograph is in the low pressure zone, one end of the injection device of the nanoliter liquid chromatograph connected to the high-pressure six-way valve is in a blocked state, and one end of the injection needle seat connected to the high-pressure six-way valve is in a blocked state.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The sampling device and sampling method of the present invention can realize nanoliter micro-sampling of any volume without loss, and can realize accurate sampling of 10 picoliter samples at the minimum.

[0021] 2. The sampling device and the sampling method of the present invention, through the flow path design, are convenient for cleaning the inner and outer walls of the sampling needle after the sample is extracted, so that the residue is as small as possible, and the cross contamination rate is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of an existing nano-liquid chromatography sample injection device.

[0023] Figure 2 It is a schematic structural diagram of the sample injection device of the present invention.

[0024] Among them, 1 is the injection needle, 2 is the small plunger, 3 is the large plunger, 4 is the tight hoop, 5 is the sealing gasket, 6 is the low-pressure body, 7 is the high-pressure body, 8 is the support ring, 9 is the cover plate, and 10 is the liquid inlet interface.

[0025] Figure 3 It is a flow chart connection diagram of the present invention when extracting samples.

[0026] Among them, 11 is a high-pressure six-way valve, 12 is a sampling needle seat, 13 represents a nanoliter liquid chromatography automatic sampling device, and 14 represents a sample bottle.

[0027] Figure 4 It is a flow path connection diagram of the present invention during sample injection.

[0028] Among them, 11 is a high-pressure six-way valve, 12 is an injection needle seat, and 13 represents a nanoliter liquid chromatography automatic injection device.

[0029] Figure 5 It is a schematic diagram of the cleaning flow path of the present invention.

[0030] Among them, 11 is a high-pressure six-way valve, 12 is a sampling needle seat, 13 represents a nanoliter liquid chromatography automatic sampling device, 14 represents a sample bottle, 15 is a cleaning tank, 16 is a peristaltic pump, 17 is a cleaning liquid bottle, and 18 is connected to a waste liquid bottle. DETAILED DESCRIPTION

[0031] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] like Figure 2 As shown, the sampling device of the nano-liquid chromatograph of the present invention comprises a sampling needle 1, a small plunger 2, a large plunger 3, a clamp 4, a sealing gasket 5, a low-pressure body 6, a high-pressure body 7, a support ring 8, a cover plate 9, and a liquid inlet interface 10. In one embodiment of the present invention, the small plunger 2 is made of tungsten alloy or 316L stainless steel, and DLC material is coated on the surface of the small plunger 2 to ensure that the small plunger 2 is incompressible. In one embodiment of the present invention, the large plunger 3 is made of sapphire or zirconium oxide material, and the clamp 4 and the sealing gasket 5 are both made of corrosion-resistant polymer materials, such as PEEK, PEI or PI.

[0034] In the present invention, a cavity for accommodating a large plunger 3 is provided in the high-pressure body 7, and the large plunger 3 is slidably connected in the cavity. The injection needle 1 can be connected to the high-pressure body 7 by a tightening fit or a welding process, and the interior of the injection needle 1 is connected to the cavity. The outer diameter of the small plunger 2 is in clearance with the inner diameter of the injection needle 1. When sampling, the sample can be sucked into the injection needle 1 under the action of the liquid surface tension and atmospheric pressure. When discharging the sample, the high-pressure mobile phase flows through the gap to discharge the sample from the injection needle 1, and the cleaning of the inner wall of the needle is achieved. The upper end of the injection needle 1 has a chamfer for guiding the small plunger 2. The lower end of the internal cavity of the high-pressure body 7 has a taper for assisting the small plunger 2 to insert the injection needle 1. The inner diameter of the injection needle 1 is extremely small, for example, 0.1 mm, and the outer diameter of the small plunger 2 matches the inner diameter of the injection needle 1, for example, the diameter is 0.08 mm. When moving 0.01 mm, accurate sampling and injection of micro samples of about 79 picoliters can be achieved, and high-pressure mobile phase can be ensured to flow through the gap.

[0035] A low-pressure body 6 is connected to the top of the high-pressure body 7, a support ring 8 is connected between the top of the low-pressure body 6 and the large plunger 3, a cover plate 9 is used to prevent the support ring 8 from falling off, and the support ring 8 and the large plunger 3 are slidably matched to ensure that the large plunger 3 can slide up and down. A sealing gasket 5 is also connected between the high-pressure body 7 and the large plunger 3, and a dynamic seal is formed between the sealing gasket 5 and the large plunger 3, and the sealing gasket 5 is compressed by a clamp 4.

[0036] The system flow path interface 10 is provided at one end of the high pressure body 7, and a straight channel connecting the system flow path interface 10 and the cavity is provided in the high pressure body 7. The bottom of the high pressure body 7 has a first surface and a second surface, both of which are planes, and the injection needle 1 is connected to the first surface, the system flow path interface 10 is provided on the second surface, the straight channel is perpendicular to the second surface, and the second surface and the first surface have an obtuse angle, for example, 135-160°.

[0037] The present invention provides a novel nano-liquid chromatography automatic sampling method, such as Figure 3 As shown, the sample injection device 13 is switched to the low pressure zone through the high pressure six-way valve 11, and the injection needle 1 on the sample injection device 13 is inserted below the liquid level of the sample bottle 14. The large plunger 3 drives the small plunger 2 to move upward to absorb the sample.

[0038] In one embodiment of the present invention, a stepper motor is used to drive a lead screw or a linear motor to drive the large plunger 3 to move up and down. A quantitative sample is extracted through a sample injection device 13. The sample bottle 14 has an inner liner tube to achieve the injection of a trace sample.

[0039] like Figure 4 As shown, the injection needle 1 is inserted into the injection needle seat 12, and the high-pressure six-way valve 11 cuts the injection device 13 into the system flow path. The injection device 13 is switched to the high-pressure area through the six-way valve 11, so that the injection device 13 is connected to the driving pump of the liquid chromatography, and the injection needle 1 is connected to the injection needle seat 12. High-pressure liquid enters from the system flow path interface 10 of the injection device 13, so that the mobile phase flows through the gap between the injection needle 1 and the small plunger 2, driving the sample from the injection needle 1 into the injection needle seat 12 and moving toward the chromatographic column.

[0040] In summary, the steps of this method are as follows:

[0041] S1, switch the sample injection device 13 to the low pressure area through the high pressure six-way valve 11, and connect the sample injection needle 1 to the sample bottle 14;

[0042] S2, the large plunger 3 in the sample injection device 13 drives the small plunger 2 to move upward to extract a quantitative sample;

[0043] S3, the injection needle 1 is inserted into the injection needle seat 12;

[0044] S4, switching the sample injection device 13 to the high pressure zone through the high pressure six-way valve 11, connecting the sample injection device 13 to the driving pump of the nanoliter liquid chromatograph, and connecting the sample injection needle 1 to the sample injection needle seat 12;

[0045] S5, high-pressure liquid enters the injection device 13 from the system flow interface 10, driving the sample from the injection needle 1 into the injection needle seat 12;

[0046] S6. The mobile phase is driven by the driving pump to flow through the gap between the injection needle 1 and the small plunger 2, and the sample is driven to move toward the chromatographic column through the injection needle seat 12.

[0047] In the present invention, when the injection device 13 is in the low pressure zone, the end of the injection device 13 connected to the high pressure six-way valve 11 is in a blocked state, and the end of the injection needle seat 12 connected to the high pressure six-way valve 11 is in a blocked state.

[0048] like Figure 5 As shown, the present invention also provides a specific implementation method for cleaning the automatic injection system, including a high-pressure six-way valve 11, an injection needle seat 12, an injection device 13 of a nanoliter liquid chromatograph, a sample bottle 14, a cleaning tank 15, a peristaltic pump 16, a cleaning liquid bottle 17, and a waste liquid bottle 18. The peristaltic pump 16 draws cleaning liquid from the cleaning liquid bottle 17 and injects it into the cleaning tank 15. The excess cleaning liquid will overflow into the channel 18 next to it and flow into the waste liquid. The injection needle on the injection device 13 extends below the liquid level of the cleaning tank 15 to clean the outer wall of the needle. The liquid inlet of the injection device 13 is connected to the fifth interface through the sixth interface of the high-pressure six-way valve 11 for sealing. The injection needle seat 12 is connected to the fourth interface through the third interface of the high-pressure six-way valve 11 for sealing.

[0049] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0050] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A sample injection device for a nano-liquid chromatograph, characterized in that: Including injection needle, small plunger, large plunger, high pressure body, system flow path interface; A cavity for accommodating a large plunger is provided in the high-pressure body, the injection needle is connected to one end of the high-pressure body and communicates with the cavity, the large plunger is slidably connected in the cavity, and the small plunger is fixedly installed at the end of the large plunger, and the diameter of the small plunger is smaller than the inner diameter of the injection needle, so that the small plunger and the inner cavity clearance of the injection needle are matched; The system flow path interface is arranged at one end of the high-pressure body, and a straight channel connecting the system flow path interface and the cavity is arranged in the high-pressure body; the bottom of the high-pressure body has a first surface and a second surface, the first surface and the second surface are both planes, and the injection needle is connected to the first surface, the system flow path interface is arranged on the second surface, the straight channel is perpendicular to the second surface, and there is an obtuse angle between the second surface and the first surface.

2. The sample injection device of the nano-liquid chromatograph according to claim 1, characterized in that: The top of the high-pressure body is connected to the low-pressure body, and a support ring is connected between the top of the low-pressure body and the large plunger, and the support ring is slidably matched with the large plunger.

3. The sample injection device of the nano-liquid chromatograph according to claim 2, characterized in that: A sealing gasket is also connected between the high pressure body and the large plunger, and a dynamic seal is formed between the sealing gasket and the large plunger. The sealing gasket is compressed by a tightening hoop.

4. The sample injection device of the nano-liquid chromatograph according to claim 3, characterized in that: A conical portion is arranged at one end of the cavity close to the injection needle, and a chamfer is arranged at the top end of the injection needle.

5. A method for injecting samples into a nano-liquid chromatograph, characterized in that: The method of injecting a sample using the sample injection device of the nano-liquid chromatograph as claimed in any one of claims 1 to 4 comprises the following steps: The sampling device of the nano-liquid chromatograph is switched to the low-pressure zone through a high-pressure six-way valve, and the sampling needle is connected to the sample bottle; A large plunger in the sample injection device of the nano-liquid chromatograph drives a small plunger to move upward to extract a quantitative sample; The injection needle is inserted into the injection needle seat; The sampling device of the nanoliter liquid chromatograph is switched to the high pressure zone through the high pressure six-way valve, the sampling device of the nanoliter liquid chromatograph is connected to the driving pump of the nanoliter liquid chromatograph, and the sampling needle is connected to the sampling needle seat; High-pressure liquid enters the sampling device of the nano-liquid chromatograph from the system flow interface, driving the sample from the injection needle into the injection needle seat; The mobile phase is driven by the driving pump to flow through the gap between the injection needle and the small plunger, driving the sample to move through the injection needle seat to the chromatographic column.

6. The sampling method of nano-liquid chromatograph according to claim 5, characterized in that: When the sampling device of the nanoliter liquid chromatograph is in the low pressure zone, the end of the sampling device of the nanoliter liquid chromatograph connected to the high-pressure six-way valve is in a blocked state, and the end of the injection needle seat connected to the high-pressure six-way valve is in a blocked state.

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