Needle washing device and needle washing method

Abstract

The present invention belongs to the field of analytical instruments, and provides a needle washing device and a needle washing method, wherein the needle washing device comprises a discharge tube and a high-frequency high-voltage generator, wherein the discharge tube is a hollow insulating tube, and a first electrode is arranged outside the discharge tube, and the first electrode is connected to the high-frequency high-voltage generator; a second electrode is arranged outside the discharge tube or not, and the second electrode is arranged at an interval with the first electrode. The needle washing process of the present invention involves chemical degradation caused by the generation of plasma and desorption and evaporation caused by sudden heating of the needle surface or inside, and the sample remaining on the inner and outer surfaces of the injection needle is instantly cleaned under the simultaneous action of multiple effects.

Description

Technical Field

[0001] The invention belongs to the field of analytical instruments, and in particular relates to an extremely fast injection needle washing device and a needle washing method. Background Art

[0002] Analytical chemistry instruments usually include one or more injection needles, which are used to quantitatively absorb samples from sample containers and then transfer the absorbed samples to detectors for analysis and detection. The sample residue on the injection needle will cause contamination and signal interference of the previous sample on the next sample, so the injection needle needs to be cleaned between completing the injection of one sample and absorbing the next sample. The conventional needle washing process is usually repeated washing with needle washing liquid, which is consumed quickly and should not be stored for too long. Suitable needle washing liquid is often required for different samples. In the entire analysis process, needle washing is often the most time-consuming step, which is generally several times longer than the time for sample aspiration and injection combined. For the traditional analysis and detection process, although needle washing takes a long time, the needle washing process is generally carried out together with the sample detection process, so the problem is not prominent, but only the needle washing liquid needs to be prepared additionally. However, for rapid detection systems, such as various direct spectroscopy, mass spectrometry, and electrochemical analysis and detection instruments, the detection time only takes one to several seconds, and the needle washing process is much longer than the detection time, and the throughput (efficiency) of the instrument is limited by the needle washing step. Therefore, speeding up the needle washing procedure is one of the urgent issues to be solved in analytical instruments.

[0003] At present, the development direction of mass spectrometry technology is in-situ ionization, micro-injection, rapid analysis, mobile on-site detection, etc. For example, MicroProbe Electro Spray Ionization (μPESI) is a special case of this development. μPESI introduces the sample through the surface of the solid needle tip, and uses high-voltage spray to ionize the sample on the needle tip to achieve mass spectrometry analysis. The μPESI ion source can simplify the sample processing steps, speed up the sample analysis speed (~10 / min), and does not require carrier gas and mobile phase. The advantages are very obvious. However, since μPESI directly ionizes a very small amount of sample through electrospray, a small amount of sample residue has a very obvious impact on the next sample signal, usually more than 30%. Therefore, for this type of micro-spray technology, the residue problem is particularly severe. Therefore, it is necessary to develop the needle washing technology for this type of spray needle.

[0004] There are two main types of injection needles used for analysis and testing, capillary hollow needles and surface adsorption solid needles. The residue after sampling by the injection needle mainly occurs at the part where the injection needle contacts the sample. For hollow needles, the residue mainly exists on the inner wall of the needle. The traditional needle washing method is to use a syringe to repeatedly absorb and squeeze out the needle washing liquid, and the liquid suction port and the extrusion port are generally separate. There is also an opening plus a switching valve to cooperate with absorption and extrusion to improve the efficiency of needle washing. There is also a method of suction and exhalation in the flowing needle washing liquid, but this method consumes a lot of needle washing liquid. The suction and exhalation needle washing not only consumes needle washing liquid and takes a long time, but also absorbs the residue into the pipeline during the liquid suction process, so that the pipeline connected to the injection needle is gradually contaminated. Therefore, the pipeline generally needs to be replaced regularly. The surface adsorption metal needle mainly achieves the purpose of cleaning the residue by immersion or flow flushing.

[0005] The above-mentioned needle washing method is not only time-consuming and consumes a large amount of needle washing liquid, but also the needle washing effect is different for different analytes, and it is often necessary to screen the appropriate needle washing liquid for the specific analyte through experiments. On the other hand, in order to improve the needle washing efficiency of the injection needle, sometimes ultrasonic or other more complex cleaning techniques are added during the needle washing process, which will inevitably increase the complexity and cost of the cleaning device. As analytical instruments are increasingly moving towards high-throughput, the existing needle washing method is increasingly becoming a bottleneck in technological development, and the needle washing technology for micro-injection needles is in urgent need of improvement. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an extremely fast needle washing device and needle washing method for a sampling needle, which combines the dielectric barrier discharge principle and uses a dual-electrode alternating voltage to quickly wash the needle. The needle washing process of the present invention involves the generation of plasma to cause chemical degradation of residual samples and sudden heating of the needle surface to cause desorption and evaporation. Under the simultaneous action of multiple effects, the samples remaining on the inner and outer surfaces of the sampling needle are instantly cleaned.

[0007] The technical problem of the present invention is solved by the following technical solutions:

[0008] A needle washing device is used to clean sample residues on an injection needle, wherein the injection needle is used for injecting analysis samples. The needle washing device comprises a discharge tube and a high-frequency high-voltage generator. The discharge tube is a hollow insulating tube. A first electrode is arranged on the outside of the discharge tube, and the first electrode is connected to the high-frequency high-voltage generator. A second electrode may or may not be arranged on the outside of the discharge tube, and the second electrode is arranged at an interval with the first electrode.

[0009] Furthermore, the discharge tube is a quartz tube, a ceramic tube, a glass tube, a carbon fiber tube or a glass fiber tube.

[0010] Furthermore, the first electrode and the second electrode are respectively conductive coatings or metal foils.

[0011] Furthermore, when the first electrode and the second electrode are simultaneously arranged outside the discharge tube, the interval between the two electrodes is set to be sufficient to ensure that no breakdown discharge occurs outside the discharge tube after high frequency and high voltage are applied.

[0012] Furthermore, the output frequency of the high-frequency and high-voltage generator is 1.5 kHz to 1 MHz, and the output voltage is 1 to 10 kilovolts.

[0013] Furthermore, when only the first electrode is arranged outside the discharge tube, the injection needle is made of a conductive material and is connected to the high-frequency high-voltage generator to form another electrode, and the tip of the injection needle is arranged in the area surrounded by the first electrode or near the upper edge of the first electrode.

[0014] Furthermore, when a second electrode is provided on the outside of the discharge tube, the second electrode is connected to the high-frequency high-voltage generator, and the second electrode is located below the first electrode, the injection needle passes through the area surrounded by the first electrode, and the tip of the injection needle is arranged in the area surrounded by the second electrode or near the upper edge of the second electrode.

[0015] On the other hand, the present invention also provides a method for washing an injection needle, wherein the injection needle is used for injecting an analytical sample. The method comprises connecting one end of a high-frequency high-voltage generator to a first electrode and the other end to a second electrode or the injection needle, and generating a dielectric barrier discharge on the surface or inside of the injection needle to clean residual samples on the surface or inside of the injection needle.

[0016] Furthermore, when the other end of the high-frequency high-voltage generator is connected to the second electrode, the injection needle passes through the area covered by the first electrode from top to bottom and the tip of the injection needle is arranged in the area covered by the second electrode or near the upper edge of the second electrode.

[0017] Preferably, when the injection needle is a hollow injection needle, airflow passes through the interior during dielectric barrier discharge.

[0018] Preferably, the dielectric barrier discharge time is 0.3 to 20 seconds.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] (1) It is extremely fast. It can reduce the residue of any injection needle to less than 1% in 1 to 10 seconds. For surface-dipping injection needles, it only takes 0.5 to 3 seconds to clean the residue to less than 1%, breaking through a technical bottleneck for the development of analytical instruments towards high throughput.

[0021] (2) Suitable for various types of injection needles, including push-in syringes (or manual injection needles), inlet pipette injection needles, injection spray needles with coatings or grooves on the surface, etc.;

[0022] (3) There is no solvent consumption, which reduces pollution and saves time in preparing needle washing solvent. It also avoids unexpected errors caused by the exhaustion of needle washing solvent during automatic operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0024] Figure 1 It is a schematic diagram of a solid injection needle washing device provided in an embodiment of the present application, in which a discharge tube is wrapped by two sections of electrodes;

[0025] Figure 2 It is a schematic diagram of a solid injection needle washing device provided in an embodiment of the present application, in which a discharge tube is wrapped by a section of electrode;

[0026] Figure 3 It is a schematic diagram of a hollow injection needle washing device provided in an embodiment of the present application, in which a discharge tube is wrapped by two sections of electrodes;

[0027] Figure 4 It is a schematic diagram of a hollow injection needle washing device provided in an embodiment of the present application, in which a discharge tube is wrapped by a section of electrode;

[0028] Markings in the figure: discharge tube 1, needle inlet 11, air inlet 12, electrode 2, first electrode 21, second electrode 22, power supply 3, injection needle 4, solid injection needle 41, hollow injection needle 42, hollow branch tube 5, sealing cap 6, sealing gasket 7. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] The present invention aims to provide an extremely fast needle washing device and method for injection needles, which combines the dielectric barrier discharge principle and uses a dual-electrode alternating voltage to quickly wash the needle. Experiments have shown that for most residual samples, the needle washing method provided by the present invention can wash the residue to less than 1% in just one second (i.e., wash away more than 99% of the residue). Conventional needle washing generally meets the requirements of most instrumental analyses as long as the residue is less than 5%, while the present invention only takes about 0.5 seconds to achieve a residue of less than 5%, and the needle washing process of the present invention does not require any needle washing solution.

[0031] The embodiment of the present invention provides a micro-injection needle washing device and a needle washing method, wherein the injection needle is used for the injection of analytical samples, and can be a hollow injection needle, or a solid injection needle. Specifically, the injection needle washing device includes a discharge tube, wherein the discharge tube is made of an insulating material, and the discharge tube can be a tube with one end closed or a tube with two ends open. At least a first electrode is arranged on the outside of the discharge tube, and the first electrode is connected to a high-frequency high-voltage generator; a second electrode is optionally arranged (arranged or not arranged) on the outside of the discharge tube, and the second electrode is connected to the high-frequency high-voltage generator. Specifically, when only one electrode is arranged on the outside of the discharge tube, the injection needle is connected to the high-frequency high-voltage generator to form another electrode.

[0032] Specifically, when two electrodes are arranged outside the discharge tube, the interval between the two electrodes (between the lower edge of the first electrode and the upper edge of the second electrode) must be sufficient to ensure that no breakdown discharge occurs outside the discharge tube after high frequency and high voltage are applied, the two electrodes are respectively connected to the two ends of the high frequency and high voltage generator, and the needle tip of the injection needle is located in the area enclosed by the second electrode or near the upper edge of the second electrode.

[0033] The embodiment of the present invention also provides a method for cleaning an injection needle, wherein the injection needle is used for sample analysis, the method comprising connecting one end of a high-frequency high-voltage generator (power supply) to a first electrode, and the other end to a second electrode or an injection needle, and generating a dielectric barrier discharge on the surface or inside of the injection needle to clean the residual sample on the surface or inside of the injection needle. When two electrodes are provided, the injection needle is not connected to the power supply, at which time the injection needle passes through the area covered by the first electrode from top to bottom and the tip of the injection needle is arranged in the area covered by the second electrode or near the upper edge of the second electrode. The time of the dielectric barrier discharge can be 0.3 to 20 seconds, preferably 0.5 to 5 seconds.

[0034] The extremely fast injection needle washing device and method provided by the present invention utilize the dielectric barrier discharge principle to quickly clean the injection needle by means of a dual-electrode alternating voltage. Experiments have shown that for most substances, the needle washing method provided by the present application can clean the sample residue to less than 1% in just one second (i.e., more than 99% of the sample residue is cleaned). Conventional needle washing generally meets the requirements of most instrumental analyses as long as the residue is less than 5%, while the present invention only takes about 0.3 seconds to achieve a residue of less than 5%, and the needle washing process of the present invention does not require the use of any needle washing solution. There are many application scenarios for plasma, but to date, no precedents for using it to clean injection needles have been found.

[0035] refer to Figure 1 , Embodiment 1 of the present invention provides a needle washing device, which includes: a discharge tube 1, electrodes 2 (including an upper first electrode 21 and a lower second electrode 22, which are spaced a certain distance apart), a power supply 3, and an injection needle 4, wherein the power supply 3 provides a high-frequency voltage to the first electrode 21 and the second electrode 22, and the body of the discharge tube 1 is made of an insulating material, which is used to block the current conducted by the electrode 2. After the power supply 3 energizes the first electrode 21 and the second electrode 22, when there is gas in the discharge tube 1, a dielectric barrier discharge will occur between the two electrodes, and at this time, the sampling part of the injection needle 41 (that is, the part with the sample remaining) is placed in the discharge field, and the residual sample on the injection needle 41 will be quickly and thoroughly cleaned. The injection needle in this embodiment can be a solid injection needle or a hollow injection needle.

[0036] The proportions shown in the drawings in this application are for illustrative purposes only and are not intended to limit the sizes of related components.

[0037] Specifically, Figure 1 The middle injection needle is a solid injection needle 41, and the discharge tube 1 is a hollow insulating tube with two openings. The inner diameter is the minimum limit to allow the solid injection needle 41 to freely enter and exit, that is, the inner diameter needs to be larger than the maximum outer diameter of the injection needle. The inner diameter is generally 1 to 20 mm, preferably 1 to 2 mm. It is made of any solid insulating material that can withstand short-term high temperature and remain non-conductive, non-deformed, and has stable mechanical properties, preferably quartz tube, ceramic tube, glass tube, carbon fiber tube, glass fiber tube, etc. The electrode 2 is arranged on the outer surface of the discharge tube 1 in a tightly wrapped manner, mainly in three ways: 1) set as a metal plating layer or graphite coating; 2) metal foil is adhered to the discharge tube 1 with conductive glue; 3) tightly sleeved on the discharge tube 1 in an extrusion manner. The power supply 3 is specifically a high-frequency high-voltage generator, and its power is determined by the material, inner diameter and wall thickness of the discharge tube 1, and is generally set to 5 to 100 watts, the output frequency is 1.5 kHz to 1 MHz, and the output voltage is 1 to 10 kilovolts. The output frequency and voltage are adjustable.

[0038] Specifically, the injection needle 41 includes a needle body and a tip portion, the needle body is set as a columnar structure, preferably the tip portion surface is engraved with one or more grooves for adsorbing samples, the grooves can be multiple parallel channels or threaded channels, the length, size and shape of the channel portion can be arbitrarily selected according to operation or installation requirements. The channel is located around the tip portion, and can carry the sample so that it does not drip during sampling and injection.

[0039] In the specific embodiment of the solid injection needle cleaning device, the inner diameter of the discharge tube 1 is 2 mm, the wall thickness is 1 mm, and the length is 10-100 mm. The electrode 2 is two sections of conductive layers (first electrode 21 and second electrode 22) wrapped on the outer surface of the discharge tube 1. The width of each electrode is 3-10 mm, and the interval between the two electrodes is about 20 mm, so as to ensure that after applying high frequency and high voltage, the electrode 21 and the electrode 22 will not break down and discharge on the outer surface of the discharge tube to generate electric sparks. Since the breakdown discharge between the two electrodes is related to the applied voltage and frequency, the wall thickness and material of the discharge tube, the temperature and humidity of the environment, etc., the specific interval needs to be selected through experiments. A wire is welded on each of the first electrode 21 and the second electrode 22, which are respectively connected to the two output ends of the high frequency and high voltage power supply 3. When the solid injection needle 41 is inserted into the discharge tube 1, the needle tip passes through the area covered by the first electrode 21, and continues downward until it approaches the upper edge of the area covered by the second electrode 22 or enters the wrapping range of the second electrode 22. In actual operation, the needle tip cannot pass through the area wrapped by the second electrode 22, otherwise no discharge occurs. Then, the high-frequency high-voltage power supply 3 is turned on, the output frequency is adjusted to 1.5KHz~1MHz, and the voltage is adjusted to about 1~4.5 kilovolts until blue or blue-purple light is seen in the discharge tube 1, and the solid injection needle 41 is allowed to stay in the discharge tube 1 in the discharge state for 0.2~3 seconds, preferably 0.5~1 second. At this time, the sample residual rate of the solid injection needle 41 drops below 1%, so that the solid injection needle 41 can move upward and leave the discharge tube 1 to perform the next sample sampling operation. In this embodiment, the injection needle can be made of conductive materials such as stainless steel, or can be made of non-conductive materials such as ceramics.

[0040] In another embodiment of cleaning a solid needle device, Figure 2As shown, the inner diameter of the discharge tube 1 is 2 mm, the wall thickness is 1 mm, and the length is 10 to 100 mm. The electrode 2 is only a conductive layer (metal layer or graphite coating) wrapped on the outer surface of the discharge tube 1. In this embodiment, the solid injection needle 41 is made of conductive material, so that the electrode 2 and the solid injection needle 41 form a pair of blocking discharge electrodes. When the injection is completed and needs to be cleaned, the solid injection needle 41 only needs to be inserted into the discharge tube 1 close to the upper edge of the electrode 2 or enter the wrapped range of the electrode 2 without exceeding the lower edge. The output frequency is further adjusted to 1.5 KHz to 1 MHz, the voltage is adjusted to about 1 to 4.5 kilovolts, and blue or blue-purple light is seen in the discharge tube 1. The solid injection needle 41 stays in the discharge tube 1 in the discharge state for 0.2 to 3 seconds, and then it can leave the discharge tube 1 to operate the next sample.

[0041] When the embodiment of the present invention is used to clean the solid injection needle 41, since the solid injection needle 41 carries a very small amount of sample solution, generally a few nanoliters to a few microliters, for example, a dip-spray dual-purpose probe often has more than 30% residual signal after each injection. When cleaned with the cleaning device of the embodiment of the present invention, the residual signal of this type of injection needle can be reduced to less than 1% within 1 second.

[0042] In a specific embodiment, the needle washing device can be matched with analytical instruments such as HPLC, GC, ICP, etc. In some embodiments, the automatic sampler is equipped with a pointed metal hollow injection needle, which is connected to a sample suction device such as a syringe or a sample suction pump through a capillary hose. For the hollow injection needle, the needle washing device of the present application is slightly different from the needle washing device of the solid injection needle.

[0043] Specifically, unlike the structure of the solid injection needle 41 , the sample residue of the hollow injection needle 42 is usually mainly present on the inner surface of the needle, and the needle washing process must allow plasma to flush the interior of the hollow injection needle 42 .

[0044] Specifically, when the hollow injection needle 42 is directly connected to the injection syringe during the injection process, the needle washing device needs to be equipped with a switching device so that the hollow injection needle 42 is connected to the syringe during the sample suction and injection, and the hollow injection needle 42 is connected to one end (upper end) of the syringe and communicates with the atmosphere during the needle washing. The switching device can be a three-way valve, or a loading and unloading device for the needle of the hollow injection needle 42, that is, when the hollow injection needle 42 is sucking and injecting, the needle that needs to contact the sample liquid is tightly connected to the loading and unloading device, and when washing the needle, the loading and unloading device automatically disengages after the needle is inserted into the discharge tube 1, so that the needle of the hollow injection needle 42 is in the discharge position in the discharge tube, and the upper end is exposed to the air. After the needle washing is completed, the loading and unloading device can connect the needle back to form a tightly connected state.

[0045] Furthermore, the present invention also provides a method for cleaning the hollow injection needle 42, firstly, the liquid in the hollow injection needle 42 is emptied by a syringe (or an injection pump), and then the hollow injection needle 42 is inserted into the discharge tube 1, and then the high-frequency high-voltage power supply 3 and the air or oxygen supply are turned on, and the air is sucked by the syringe (or the injection pump), and the plasma generated by the needle tip is sucked into the needle hole to clean the inner surface. In the embodiment of the device for cleaning the hollow injection needle 42, as Figure 3 As shown, the discharge tube 1 is a sealed hollow tube made of insulating material, with an inner diameter of 3 mm, a wall thickness of 2 mm, and a length of 10 to 100 mm. The discharge tube 1 can be made of any solid insulating material that can withstand short-term high temperature and remain non-conductive, non-deformed, and has stable mechanical properties, preferably a quartz tube, a ceramic tube, a glass tube, a carbon fiber tube, a glass fiber tube, etc. At least one needle inlet 11 and an air inlet 12 are arranged on the tube, and the tube port is provided with a sealing cap 6, and a through hole is arranged at the top of the sealing cap 6. A sealing gasket 7 is placed in the sealing cap 6, wherein the sealing gasket 7 can be replaced by a soft plug or a bottle cap with an opening on the top. The sealing gasket 7 is tightly sleeved on the upper end of the discharge tube 1 by the sealing cap 6, and the through hole is sealed. The opening on the sealing gasket 7 allows the hollow injection needle 42 to be inserted and pulled out.

[0046] Specifically, the needle inlet 11 is arranged on the sealing gasket 7 at the opening at one end on the radial axis of the discharge tube 1, and the hollow injection needle 42 pierces the sealing gasket 7 and enters the discharge tube 1. When the hollow injection needle 42 is inserted into the discharge tube 1 through the needle inlet 11, the needle body and the radial axis of the discharge tube 1 are basically overlapped and the needle inlet 11 is guaranteed to be airtight. The air inlet 12 can be arranged at any part of the discharge tube 1, and is used to introduce gas into the discharge tube 1 and keep the discharge tube 1 sealed. The body of the discharge tube 1 in the figure is provided with a hollow branch tube 5, one end of which is connected to the inside of the discharge tube 1 and the other end is connected to the gas source. In other embodiments, a tube with two ends opened can be inserted at the needle inlet 11 parallel to the needle insertion direction, one end of which is connected to the inside of the discharge tube 1 and the other end is connected to the gas source, wherein the gas source can be oxygen or air.

[0047] Furthermore, in other specific embodiments, in the needle washing device for the hollow injection needle 42, the discharge tube 1 can be configured as a hollow tube with openings at both ends, and the gas inlet 12 can be configured at the other end opposite to the needle inlet 11 for connecting to a gas source and inputting gas.

[0048] Specifically, Figure 3As shown, when cleaning the hollow injection needle 42, the electrode 2 is a conductive layer wrapped around the outer surface of the discharge tube 1 in two sections: the first electrode 21 and the second electrode 22, with a width of 3 to 10 mm, respectively, and the interval between the two conductive layers is about 20 mm. A wire is welded on each electrode and connected to the two output ends of the high-frequency high-voltage power supply 3. The hollow branch pipe 5 is connected to the gas source of pure air or oxygen, and the gas supply pressure is adjusted to be slightly higher than the ambient pressure, so that the air flow can flow out from the upper end of the hollow injection needle 42, so that the plasma can enter the inside of the injection needle during cleaning. When the needle pump drives the injection needle to suck and inject samples, the needle pump is connected to one interface of the three-way electromagnetic valve through a polytetrafluoroethylene capillary, the hollow injection needle 42 is connected to another interface, and the third interface of the three-way electromagnetic valve is connected to the atmosphere through a filter (the needle pump and the connecting device are not marked in the figure). When washing the needle, the three-way solenoid valve is switched to a state where the hollow injection needle 42 is connected to the atmosphere and the needle pump interface is blocked. The hollow injection needle 42 pierces the sealing pad 7 and enters the discharge tube 1 until the needle tip of the hollow injection needle 42 approaches or extends to but does not penetrate the area surrounded by the bottom electrode 2 of the discharge tube 1. At this time, air or oxygen is introduced and the high-frequency high-voltage power supply 3 is turned on. The output frequency is adjusted to 1.5KHz~1MHz, and the voltage is adjusted to about 1~5 kilovolts until a blue-purple light is seen in the discharge tube 1. The hollow injection needle 42 is allowed to stay in the discharge tube 1 in the discharge state for 0.5~20 seconds, preferably 1~5 seconds, so that the residue on the hollow injection needle 42 can be reduced to less than 1%. Then the three-way solenoid valve is switched to a state where the needle pump is connected to the hollow injection needle 42 and the interface to the atmosphere is blocked. The hollow injection needle 42 moves upward to leave the discharge tube 1 for the next injection operation.

[0049] In another embodiment of cleaning the hollow needle device, Figure 4As shown, the discharge tube 1 is also a sealed hollow tube made of insulating material, with an inner diameter of 3 mm, a wall thickness of 2 mm, and a length of 10 to 100 mm. The discharge tube 1 can be made of any solid insulating material that can withstand short-term high temperature and remain non-conductive, non-deformed, and has stable mechanical properties, preferably a quartz tube, a ceramic tube, a glass tube, a carbon fiber tube, a glass fiber tube, etc. At least one needle inlet 11 and an air inlet 12 are provided on the tube, and the tube port is provided with a sealing cap 6 with a central through hole, and a sealing gasket 7 is placed in the sealing cap 6 to seal the through hole and the needle inlet. The electrode 2 is merely a conductive layer (metal layer or graphite coating) wrapped around the outer surface of the discharge tube 1. In this embodiment, the hollow injection needle 42 is made of a conductive material to form another electrode opposite to the conductive layer. In this way, the electrode 2 and the hollow injection needle 42 form a pair of electrodes. When cleaning, the liquid inside the hollow injection needle 42 is first emptied into the waste liquid with a needle pump, and then the hollow injection needle 42 is inserted into the discharge tube 1 close to the upper edge of the electrode 2 or into the wrapped range of the electrode 2 without exceeding the lower edge of the electrode 2. The wire of the electrode 2 is connected to one output end of the high-frequency high-voltage power supply 3, and the other output end of the high-frequency high-voltage power supply 3 is electrically connected to the hollow injection needle 42. Air or oxygen is introduced and the power supply 3 is turned on. The output frequency is adjusted to 1.5KHz~1MHz, and the voltage is adjusted to about 1~5 kilovolts. When bluish-purple light is seen in the discharge tube 1, a needle pump is used to suck air at the same time, and the plasma is sucked into the needle for cleaning. The hollow injection needle 42 is allowed to stay in the discharge tube 1 in the discharge state for 0.5~20 seconds, preferably 1~5 seconds. The sample residue on the hollow injection needle 42 can be reduced to less than 1%, and then the discharge tube 1 can be left for the next sample injection operation.

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

Claims

1. A needle washing device for cleaning sample residues on a sampling needle, wherein the sampling needle is used for sampling an analytical sample, characterized in that: The needle washing device comprises a discharge tube and a high-frequency high-voltage generator, wherein the discharge tube is a hollow insulating tube, a first electrode is arranged outside the discharge tube, and the first electrode is connected to the high-frequency high-voltage generator; a second electrode is arranged outside the discharge tube, and the second electrode is arranged at a distance from the first electrode; The injection needle is a hollow injection needle, the discharge tube is in a sealed state, and the discharge tube body is provided with a hollow branch tube, one end of the hollow branch tube is connected to the inside of the discharge tube, and the other end is connected to the gas source, and the needle washing device also includes a sealing pad and a three-way solenoid valve; When the needle pump drives the injection needle to aspirate or inject a sample, one interface of the three-way solenoid valve is connected to the needle pump through a polytetrafluoroethylene capillary, another interface is connected to the hollow injection needle, and the third interface is connected to the atmosphere through a filter; When washing the needle, the three-way solenoid valve is switched to a state where the hollow injection needle is connected to the atmosphere and the needle pump interface is blocked, the hollow injection needle pierces the sealing pad and enters the discharge tube, and the needle tip of the hollow injection needle approaches or extends to but does not penetrate the area surrounded by the electrode at the bottom of the discharge tube; After the cleaning is completed, the three-way solenoid valve is switched to a state in which the needle pump is connected to the hollow injection needle and the interface leading to the atmosphere is blocked.

2. The needle washing device according to claim 1, characterized in that: The discharge tube is a quartz tube, a ceramic tube, a glass tube, a carbon fiber tube or a glass fiber tube.

3. The needle washing device according to claim 1, characterized in that: The first electrode and the second electrode are conductive coatings or metal foils.

4. The needle washing device according to claim 1, characterized in that: The interval between the two electrodes is set to prevent breakdown discharge from occurring on the outer surface between the two electrodes.

5. The needle washing device according to claim 1, characterized in that: The power of the high-frequency high-voltage generator is 5 to 100 watts, the output frequency is 1.5 kHz to 1 MHz, and the output voltage is 1 to 10 kilovolts.

6. The needle washing device according to claim 1, characterized in that: The second electrode is connected to the high-frequency high-voltage generator and is located below the first electrode. The injection needle passes through the area surrounded by the first electrode, and the tip of the injection needle is arranged in the area surrounded by the second electrode or near the upper edge of the second electrode.

7. The needle washing device according to claim 6, characterized in that: During dielectric barrier discharge, air flows inside.

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