SPME sample injection needle automatic protection device based on dielectric resistance jump detection

Abstract

The utility model provides an SPME sample injection needle automatic protection device based on dielectric resistance jump detection, which comprises a sample injection driving assembly and an SPME sample injection needle, the sample injection driving assembly is used for driving the SPME sample injection needle to integrally move, the SPME sample injection needle comprises a hard protection tube and a fiber head assembly, the hard protection tube is axially and movably sleeved outside the fiber head assembly, and the fiber head assembly is sleeved outside the hard protection tube. The protective cover is used for protecting the fiber head assembly in a non-sample injection state and exposing the fiber head assembly in a sample injection state; the device further comprises a dielectric resistance detection assembly and a control unit. The dielectric resistance detection assembly comprises two detection electrodes which are arranged at the front end of the hard protection tube and are used for sensing dielectric resistance value changes, and the two detection electrodes are connected with the control unit through conductors; and the control unit controls the sample injection driving assembly to stop feeding according to whether the received medium resistance value change exceeds a threshold value or not. The device has the advantages that the sampling of the SPME sample injection needle is more flexible, and the fiber head of the SPME sample injection needle is prevented from being immersed and damaged.

Description

TECHNICAL FIELD

[0001] The utility model relates to tobacco chemical analysis technical field, specifically, relate to a kind of SPME sampling needle automatic protection device based on medium resistance jump detection. BACKGROUND

[0002] As a new sample pretreatment method, solid phase microextraction (SPME) technology has been widely used in environmental detection, food safety, drug analysis and other fields due to its advantages such as no solvent, simple operation, small sample size and suitability for volatile and non-volatile substance analysis.

[0003] The SPME sampling needle is generally composed of a metal needle tube and a fiber head coated with an adsorbent inside. The metal needle tube is used to pierce the headspace bottle and protect the fiber head. The fiber head can be extended from the metal needle tube. The fiber head is the key component for collecting volatile and non-volatile substances.

[0004] However, due to the small and fragile structure of the fiber head, especially when measuring aqueous solution samples, the fiber head is easily damaged once it comes into contact with liquid, resulting in reduced adsorption effect and data accuracy, which further affects the reliability of the overall analysis results.

[0005] The existing SPME automatic sampling device is used in tobacco chemical analysis. The headspace bottle containing the solution to be measured is placed below the sampling needle. The sampling needle is driven to a set stroke parameter and then inserted into the headspace bottle to a set depth. The fiber head is then exposed to sample volatile substances.

[0006] This method has operational risks in our laboratory. The reason is that tobacco chemical analysis involves diversified solutions, which makes the sampling process of the headspace bottle mainly rely on manual sampling. Manual sampling is unstable in controlling the amount of solution collected. When the sampling needle is fed according to the preset stroke, if the sample is too much, the sampling needle will be inserted below the liquid surface during the preset stroke feeding, which will cause the fiber head to be submerged and damaged, increase the cost, and also cause the sampling quality to decrease, which is not conducive to stable experiment.

[0007] To solve the above problems and avoid the fiber head from being submerged and damaged, the existing SPME sampling needle needs to be modified. UTILITY MODEL CONTENT

[0008] The utility model aims at the deficiencies of the prior art, and provides an SPME sampling needle automatic protection device based on medium resistance jump detection, which is more flexible in sampling and avoids the fiber head of the SPME sampling needle from being submerged and damaged.

[0009] In order to achieve the above object, the utility model adopts the technical scheme, which is a SPME sampling needle automatic protection device based on medium resistance jump detection, comprising a sampling driving assembly and a SPME sampling needle, the sampling driving assembly is used for driving the whole SPME sampling needle to move, the SPME sampling needle comprises a hard protection tube and a fiber head assembly, the hard protection tube can be axially movable and is sleeved outside the fiber head assembly, and is used for protecting the fiber head assembly in the non-sampling state and exposing the fiber head assembly in the sampling state, further comprising a medium resistance detection assembly and a control unit,

[0010] The medium resistance detection assembly comprises two detection electrodes arranged at the front end of the hard protection tube and used for sensing the medium resistance value change, and the two detection electrodes are connected to the control unit through a conductor.

[0011] The control unit controls whether the sampling driving assembly stops feeding according to whether the received medium resistance value change is over the threshold value.

[0012] As described above, the material of the hard protection tube is a hard plastic tube or a metal tube.

[0013] As described above, the detection electrodes are arranged on the opposite sides of the hard protection tube.

[0014] As described above, the farthest point of the detection electrode is arranged at least 1cm beyond the frontmost edge of the hard protection tube.

[0015] As described above, the farthest point of the detection electrode is aligned with the frontmost edge of the hard protection tube.

[0016] As described above, two long grooves are arranged on the opposite sides of the hard protection tube, the conductor is a metal sheet, the metal sheet is embedded in the long groove, and the detection electrode is installed at the frontmost end of the metal sheet.

[0017] As described above, when the hard protection tube is a metal tube, the metal sheet and the metal tube are isolated by an insulating material.

[0018] As described above, a wire groove is formed in the side wall of the hard protection tube, the conductor is a wire, and the detection electrode is connected to the control unit through the wire; when the hard protection tube is a metal tube, the wire is wrapped with an insulating layer, and the detection electrode is fixed to the side wall of the hard protection tube through the insulating glue.

[0019] As described above, the front end of the detection electrode is a sharp end.

[0020] As described above, the control unit is a control unit of the SPME automatic sampling device.

[0021] The utility model has substantial features and progress compared with the prior art, specifically, the utility model has the following advantages:

[0022] 1. On the basis of the original SPME sampling needle, two detection electrodes are arranged at the front end of the hard protective tube, the detection electrodes are used for detecting the change of medium resistance value, if the liquid level in the headspace bottle is high, when the SPME sampling needle enters the headspace bottle and advances according to the set stroke, the detection electrode first contacts the liquid surface to cause the resistance value to change, and the control unit immediately controls the sampling needle to stop feeding, thereby avoiding the problem that the fiber head assembly is contaminated by the solution due to the fiber head pollution caused by the sampling needle continuing to feed according to the set stroke, and since the feeding stroke is no longer fixed, the sampling is relatively more flexible.

[0023] 2. Since the hard protective tube needs to pierce the headspace bottle, the material needs to have a certain hardness, so metal tubes or hard plastic tubes are often selected, when metal tubes are used, the detection of the detection electrode will be disturbed, so a certain insulation structure needs to be arranged for isolation to avoid short circuit interference. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is the overall schematic view of the SPME sampling needle in the utility model.

[0025] Figure 2 It is the fiber head assembly extension state schematic view of the SPME sampling needle in the utility model.

[0026] Figure 3 It is the local structure schematic view of the detection electrode in the SPME sampling needle automatic protection device based on medium resistance jump detection in the utility model.

[0027] Figure 4 It is the local structure schematic view of the detection electrode in the SPME sampling needle automatic protection device based on medium resistance jump detection in other embodiments of the utility model.

[0028] Figure 5 It is the local structure schematic view of the detection electrode in the SPME sampling needle automatic protection device based on medium resistance jump detection in some embodiments of the utility model.

[0029] In the drawing: 1. Hard protective tube;2. Fiber head assembly;3. Detection electrode;4. Wire;5. Metal sheet;11. Embedding groove;12. Insulating glue. DETAILED DESCRIPTION

[0030] The technical scheme of the utility model will be described in further detail below through specific embodiments.

[0031] For example, Figures 1-3As shown, an automatic protection device for SPME injection needle based on dielectric resistance jump detection includes an injection drive component, an SPME injection needle, a dielectric resistance detection component, and a control unit. The injection drive component is used to drive the SPME injection needle to move as a whole. The SPME injection needle includes a rigid protective tube 1 and a fiber head assembly 2. The rigid protective tube 1 is axially movable and fitted outside the fiber head assembly 2 to protect the fiber head assembly 2 in the non-injection state and expose the fiber head assembly 2 in the injection state.

[0032] Among them, the rigid protective tube 1 and the fiber head assembly 2 are the basic structures of the existing SPME injection needle. The fiber head assembly 2 is assembled from the needle tube and the fiber head. The needle tube is located at the rear end, and the fiber head is connected to the end of the needle tube to form a sampling needle. The fiber head is relatively soft and its surface is coated with an adsorbent for collecting target compounds.

[0033] The rigid protective tube 1 is a needle with a larger inner diameter. In the prior art, it is made of metal tube, such as stainless steel. Its main purpose is to protect the fiber head assembly. When entering the headspace vial, the fiber head assembly retracts inside the rigid protective tube. After piercing the headspace vial and entering the interior, the fiber head assembly extends out from the rigid protective tube 1 to take samples. The samples are mainly volatile substances.

[0034] The dielectric resistance detection component includes two detection electrodes 3 disposed at the front end of the rigid protective tube for sensing changes in dielectric resistance. The two detection electrodes 3 are connected to the control unit via conductors.

[0035] In this embodiment, the rigid protective tube 1 is designed as a metal tube, the same as in the prior art. The detection electrode 3 is attached to both sides of the rigid protective tube 1 with insulating adhesive. To improve structural stability, a groove 11 can be made on the side wall of the rigid protective tube 1. The detection electrode 3 is inserted into the groove 11 and fixed with insulating adhesive 12, so that the end diameter of the rigid protective tube 1 is kept within a relatively small range.

[0036] The conductor is a wire with an insulating layer on its surface. It is laid as close as possible to the surface of the rigid protective tube 1. Alternatively, a groove can be cut into the surface of the rigid protective tube 1 for wiring.

[0037] In other embodiments, such as Figure 4 As shown, the detection electrode 3 can also be fixed on the inner side of the rigid protective tube 1, but it should not interfere with the movement of the fiber head assembly, and the wires should also run from the inside.

[0038] In some embodiments, such as Figure 5As shown, two long grooves in notch style are formed on both sides of the hard protective tube 1, the detection electrode 3 is installed in the long groove and fixed at the notch position of the long groove through insulation material such as insulating glue, and the whole is packaged to form a hard protective tube 1 assembled as a whole, and the conductor can also be selected as a metal sheet, which is used to fill the long groove notch to form a closed protective tube overall structure.

[0039] In other embodiments, the material of the hard protective tube 1 is designed as a hard plastic tube, which is an insulating material itself, so that further insulation treatment means is not needed, and thus the connection mode of the detection electrode and the hard protective tube can be diversified, such as through gluing, fusing, locking, and embedding.

[0040] The control unit controls whether the sample feeding driving assembly stops feeding according to whether the received medium resistance value change is over the threshold value.

[0041] In this embodiment, the control unit is the self-provided control unit of the SPME automatic sampling device, and the scheme only increases one input signal of signal acquisition compared with the original control unit, the original host is provided with more data access ports, one of which can be selected, and the program module is modified so that the data of the road can be collected, which is easy for those skilled in the art.

[0042] The sample feeding driving assembly is generally a motor and a linear guide rail, or a linear motion mechanism such as a gas cylinder or an electric cylinder. In the past, the control mode was to set a fixed stroke value. In this embodiment, a protection signal is added, that is, the medium resistance change signal collected by the detection electrode, to provide safety protection.

[0043] In a more specific design form, in this embodiment, the farthest point of the detection electrode 3 is set to be at least 1 cm beyond the frontmost edge of the hard protective tube 1, which aims to sense the liquid level position as early as possible and leave more safety margin.

[0044] Since the process of piercing the headspace bottle is a force process, in order to avoid the detection electrode being blocked and damaged, in this embodiment, the front end of the detection electrode is a sharp end, which is more likely to pierce the cover of the headspace bottle and avoid damage to the detection electrode.

[0045] Of course, in other embodiments, the farthest point of the detection electrode is aligned with the frontmost edge of the hard protective tube, which can also solve the technical problem while maintaining the length parameter of the original hard protective tube.

[0046] Working principle explanation:

[0047] In the specific work of tobacco chemical component analysis, due to the need for extensive data comparison, the diversification of sampling data is required, but due to the significant characteristics of the work, which are large in quantity and variety, it is difficult to perform by automatic means, so the solution is prepared by manual method, the prepared solution is injected into the headspace bottle and packaged, since it is manually injected, the control of the injection amount is unstable, and there are always a small amount of solutions in the headspace bottle exceeding the required liquid level height, even if these headspace bottles can be checked and removed in the subsequent inspection process, but it is more difficult to prepare the sample according to the requirements, directly removing it will lead to the lack of part of the data in the experiment, and insisting on sampling will lead to the technical problem that the fiber head assembly is easily damaged when the liquid level is too high.

[0048] In the specific implementation process of the scheme, the selected headspace bottle to be tested is placed below the SPME sampling needle, the SPME automatic sampling device is started, the SPME sampling needle is lowered according to the set stroke value, and after piercing the headspace bottle and entering the inside of the headspace bottle, it continues to advance according to the set stroke.

[0049] When the solution liquid level height is higher than the set value, during the advancing process, the detection electrode 3 will first be immersed below the liquid level, the resistance between the detection electrodes 3 changes from infinity to a relatively small value, and a significant change occurs, and the control unit obtains a change value that exceeds the preset threshold value, so it can be judged that the liquid level will be contacted, and feedback to the sampling drive assembly is immediately made to control the sampling drive assembly to stop feeding.

[0050] When the length of the detection electrode 3 is set to be relatively long, the fiber head assembly can be directly sampled by controlling the extension length.

[0051] When the length of the detection electrode 3 is set to be relatively short, the sampling drive assembly can be controlled to move up a small distance, and after being separated from the liquid level by a certain height, the fiber head assembly is extended for sampling.

[0052] This means effectively solves the problem that the fiber head is easily damaged due to the high liquid level, and makes the sampling flexibility higher.

[0053] Finally, it should be noted that: the above examples are only used to illustrate the technical scheme of the present application, but not to limit it; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical scheme of the present application, all should be covered in the technical scheme range of the present application claimed by the present application.

Claims

1. An automatic protection device for SPME sampling needle based on medium resistance jump detection, comprising a sampling driving assembly and a SPME sampling needle, the sampling driving assembly is used to drive the whole movement of the SPME sampling needle, the SPME sampling needle comprises a hard protection tube and a fiber head assembly, the hard protection tube is axially movable and sleeved outside the fiber head assembly, and is used to protect the fiber head assembly in a non-sampling state and expose the fiber head assembly in a sampling state; characterized in that: The medium resistance detection assembly and the control unit are further included; ​ The medium resistance detection assembly includes two detection electrodes arranged at the front end of the hard protection tube for sensing the change of the medium resistance, and the two detection electrodes are connected to the control unit through a conductor; The control unit controls whether the sample driving assembly stops feeding according to whether the received change of the medium resistance exceeds a threshold value.

2. The automatic protection device for SPME sampling needle based on dielectric resistance jump detection according to claim 1, characterized in that: The material of the hard protection tube is a hard plastic tube or a metal tube.

3. The SPME needle automatic protection device based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: The detection electrodes are arranged on opposite sides of the hard protection tube.

4. The SPME needle automatic protection device based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: The farthest point of the detection electrode is arranged at least 1 cm beyond the front edge of the hard protection tube.

5. The SPME needle automatic protection device based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: The farthest point of the detection electrode is aligned with the front edge of the hard protection tube.

6. The SPME needle auto-protection device based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: Two long grooves are arranged on opposite sides of the hard protection tube, the conductor is a metal sheet, the metal sheet is embedded in the long groove, and the detection electrode is installed at the front end of the metal sheet.

7. The automatic protection device for SPME sampling needle based on dielectric resistance jump detection according to claim 6, characterized in that: When the hard protection tube is a metal tube, the metal sheet is isolated from the metal tube by an insulating material.

8. The automatic protection device for SPME sampling needle based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: A wire groove is formed in the side wall of the hard protection tube, the conductor is a wire, and the detection electrode is connected to the control unit through the wire; when the hard protection tube is a metal tube, the wire is wrapped with an insulating layer, and the detection electrode is fixed to the side wall of the hard protection tube through insulating glue.

9. The automatic protection device for SPME sampling needle based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: The front end of the detection electrode is a sharp end.

10. The automatic protection device for SPME sampling needle based on dielectric resistance jump detection according to claim 1 or 2, characterized in that: The control unit is a control unit provided with an SPME automatic sampling device.

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