An automatic solid-phase extraction device and its control method

Abstract

The present invention relates to an automatic solid-phase extraction device and its control method, including a base (1), characterized in that: two clamping plates (4) are provided on the base (1), and the two clamping plates can move towards each other under the action of a clamping driving mechanism to clamp a test tube, and can also move in the reverse direction to release the test tube; the clamping plate (4) clamping the test tube can be tilted under the action of a rotating mechanism, so that the wastewater inside the test tube is tilted and poured out. When the wastewater inside the test tube needs to be collected in the present invention, the transfer, clamping and fixing, and pouring of the test tube can be automatically realized, and the above steps can all be realized by automatic operation, avoiding the situation of sequentially removing the test tubes for wastewater collection, reducing the working intensity, and having a high wastewater collection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field related to solid phase extraction, in particular to an automatic solid phase extraction device and a control method thereof. Background Art

[0002] Solid-Phase Extraction (SPE) is a sample pretreatment technology developed in recent years. It is developed by combining liquid-solid extraction columns and liquid chromatography technology. It is mainly used for sample separation, purification and concentration. Compared with traditional liquid-liquid extraction, it can improve the recovery rate of analytes, more effectively separate analytes from interfering components, reduce sample pretreatment processes, and is simple to operate, time-saving and labor-saving. It is widely used in the fields of medicine, food, environment, commodity inspection, chemical industry, etc.

[0003] The existing solid phase extraction process includes small column activation, sample loading, cleaning, and elution. Among them, the small sample activation wastewater and cleaning wastewater are mainly collected through wastewater pipes. However, the existing test tube racks are usually supporting types, that is, a plurality of fixed slots are opened on the test tube rack, and the test tubes are fixed on the test tube rack by plugging. The wastewater pipes need to be removed one by one to collect the wastewater, which not only has high work intensity, but also has low wastewater collection efficiency.

[0004] Prior art Chinese patent document: CN213669426U, entitled "A Multifunctional Test Tube Rack for Fully Automatic Solid Phase Extraction", discloses a process for extracting wastewater from a test tube by means of a catheter and a water pump. However, the process requires manual insertion of the catheter into the test tube, and the clamping plate clamping cannot achieve automatic control. Summary of the invention

[0005] The present invention designs an automatic solid phase extraction device and a control method thereof, which solves the technical problem that the automatic solid phase extraction device in the prior art needs to lead out test tube wastewater and cannot be automated, and the test tube clamping cannot be automatically controlled.

[0006] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0007] An automatic solid phase extraction device includes a base, characterized in that: two clamping plates are arranged on the base, and the two clamping plates can move towards each other to clamp a test tube under the action of a clamping drive mechanism, and can also move in the opposite direction to release the test tube; the clamping plates clamping the test tube can be tilted under the action of a rotating mechanism, so that waste water inside the test tube can be tilted and poured out.

[0008] Preferably, the clamping drive mechanism includes a first bidirectional lead screw, which is installed in the mounting hole of the square support frame through bearings. One end of the first bidirectional lead screw is connected to the motor shaft of the first motor, and the bottom of the first motor is connected to the square support frame through a support plate. The threads of the first bidirectional lead screw are connected to a first thread sliding sleeve and a second thread sliding sleeve, and the first thread sliding sleeve and the second thread sliding sleeve are respectively connected to a clamping plate. The first thread sliding sleeve and the second thread sliding sleeve also cause the two clamping plates to clamp or release the test tube through reverse or forward movement.

[0009] Preferably, the clamping drive mechanism includes a second bidirectional lead screw, which is installed in the mounting hole of the square support frame through bearings. One end of the second bidirectional lead screw is connected to the motor shaft of the second motor, and the bottom of the second motor is connected to the square support frame through a support plate. The threads of the second bidirectional lead screw are connected to a third thread sliding sleeve and a fourth thread sliding sleeve, and the third thread sliding sleeve and the fourth thread sliding sleeve are respectively connected to a clamping plate. The third thread sliding sleeve and the fourth thread sliding sleeve also cause the two clamping plates to clamp or release the test tube through reverse or forward movement; the first bidirectional lead screw and the second bidirectional lead screw are located on both sides of the clamping plate and work synchronously.

[0010] Preferably, both clamping plates are provided with clamping holes, and the two clamping holes cooperate with each other to clamp the test tube.

[0011] Preferably, one side of the inner wall of the semi - circle of the clamping hole is made of a telescopic elastic material, and a pressure sensor is provided on the inner wall of the other semi - circle. The output value of the pressure sensor is sent to the control unit, and the control unit thereby determines whether the test tube is clamped too tightly or not.

[0012] Preferably, it further includes a rotating mechanism for pouring the sewage in the test tube. The rotating mechanism includes a first magnetic attachment, two support plates, a first rotating shaft, a second rotating shaft, and an electromagnet. The two ends of the square support frame are respectively connected to the first rotating shaft and the second rotating shaft. The first rotating shaft is connected to the mounting hole of a support plate through bearing A, and the second rotating shaft is connected to the mounting hole of the other support plate through bearing B. The first rotating shaft and the second rotating shaft are coaxial so that the square support frame can rotate; a first magnetic attachment is provided at the other end of the first bidirectional lead screw, and an electromagnet is provided above and / or below the first magnetic attachment. When the pressure value output by the pressure sensor indicates that the test tube is clamped, the control unit controls the electromagnet to be energized, and the first magnetic attachment is adsorbed by the electromagnet, and the square support frame and the test tube on it are tilted to pour out the waste water.

[0013] Preferably, there are two electromagnets, one is located above the first magnetic attachment, and the other is located below the first magnetic attachment. The distances between the two first magnetic attachments and the electromagnets are different. The electromagnet with a longer distance can make the angle between the square support frame and the horizontal plane larger, so that more waste water is poured out of the test tube, and the electromagnet with a shorter distance can make the angle between the square support frame and the horizontal plane smaller, so that less waste water is poured out of the test tube.

[0014] Preferably, it further includes a plurality of support rods, one end of each support rod is connected to a support plate; a water guide plate inclined downward and inward is provided on the support rod, connecting plates connected to the support rod are provided at both ends of the water guide plate, and a water collecting cavity for collecting waste water is formed at the top end of the base; a water collecting plate inclined inward is provided at the lowest end of the water guide plate, and baffle plates connected to the support rod are provided at both ends of the water collecting plate; a drain hopper inclined downward is provided at the bottom end of the base, a drain pipe is provided at the bottom end of the drain hopper, a control valve is provided on the drain pipe, and support legs are provided at the bottom end of the base.

[0015] A control method for an automatic solid-phase extraction device includes the following steps:

[0016] Step 1: When the test tube clamping mechanism moves the lower end of the test tube to the clamping hole, the control unit controls the first motor and the second motor to work synchronously, so that the two clamping plates move towards each other and gradually approach the lower end of the test tube;

[0017] Step 2: After the two clamping plates clamp the lower end of the test tube, the pressure sensor starts to send pressure values to the control unit. When the pressure value reaches A, the test tube clamping mechanism completely releases the test tube and moves it away;

[0018] Step 3: When the pressure value output by the pressure sensor reaches B, B > A, the control unit controls the first motor and the second motor to stop working, indicating that the test tube is clamped;

[0019] Step 4: The control unit activates the electromagnet, so that the first magnetic attachment on the first bidirectional lead screw is adsorbed, and at the same time drives the two clamping plates and the test tube to rotate and tilt to pour out the waste water.

[0020] Preferably, after step 3 is completed, the waste water in the test tube is located in the upper layer and the solution is located in the lower layer; the image acquisition device acquires a picture of the height of the waste water in the test tube and sends it to the control unit. The control unit determines which electromagnet to activate according to the height of the waste water. The distances between the two first magnetic attachments and the electromagnet are different. The electromagnet with a longer distance can make the angle between the square support frame and the horizontal plane larger, so that the test tube pours out more waste water, and the electromagnet with a shorter distance can make the angle between the square support frame and the horizontal plane smaller, so that the test tube pours out less waste water.

[0021] The automatic solid-phase extraction device and its control method have the following beneficial effects:

[0022] (1) When the waste water inside the test tube needs to be collected in the present invention, the transfer, clamping and fixing, and pouring of the test tube can be automatically realized, and the above steps can all be realized automatically, avoiding the situation of taking down the test tubes one by one for waste water collection, reducing the work intensity, and having high waste water collection efficiency.

[0023] (2)The present invention can also determine the amount of waste water in the test tube, so as to select different electromagnets to make the inclination angle of the test tube different, meeting different pouring amounts.

[0024] (3)In the automatic control of the present invention, the pressure sensor can not only serve as a judging device for clamping and fastening the test tube, but also as a judging device for subsequent pouring of waste water, and closely combines clamping and pouring, cooperating and supporting each other to achieve reliable automatic control. Description of the Drawings

[0025] Figure 1 : Three-dimensional schematic diagram of the automatic solid-phase extraction equipment of the present invention;

[0026] Figure 2 : Structural schematic diagram of the automatic solid-phase extraction equipment of the present invention;

[0027] Figure 3 : Schematic diagram of the non-inclined clamping plate in the present invention;

[0028] Figure 4 : Schematic diagram of the inclined clamping plate in the present invention;

[0029] Figure 5 : Cross-sectional view of the base structure of the automatic solid-phase extraction equipment of the present invention.

[0030] Description of the Reference Numerals:

[0031] 1 - Base; 2 - Support Rod; 3 - Support Plate; 4 - Clamping Plate; 5 - Clamping Hole; 6 - First Motor; 7 - Second Motor; 8 - Rotating Plate; 9 - Pressure Sensor; 10 - First Bi-directional Screw Rod; 11 - First Threaded Sliding Sleeve; 12 - Second Threaded Sliding Sleeve; 13 - First Magnetic Attachment; 14 - Water Guide Plate; 15 - Connecting Plate; 16 - Water Collection Chamber; 17 - Water Collection Plate; 18 - Water Baffle; 19 - Drain Hopper; 20 - Drain Pipe; 21 - Control Valve; 22 - Support Leg; 23 - Third Threaded Sliding Sleeve; 24 - Fourth Threaded Sliding Sleeve; 25 - Second Bi-directional Screw Rod; 26 - Second Magnetic Attachment; 27 - First Rotating Shaft; 28 - Second Rotating Shaft; 29 - Square Frame Support; 30 - Support Frame; 31 - Electromagnet. Detailed Embodiments

[0032] The following is a further description of the present invention in conjunction with Figures 1 to 5 , as follows:

[0033] As Figure 1 shown, an automatic solid-phase extraction equipment includes a base 1. Two clamping plates 4 are provided on the base 1. The two clamping plates can move towards each other under the action of a clamping driving mechanism to clamp the test tube, and can also move in the reverse direction to release the test tube; the clamping plate 4 for clamping the test tube can be inclined under the action of a rotating mechanism, so that the waste water inside the test tube is poured out obliquely.

[0034] It also includes multiple support rods 2, one end of which is connected to a support plate 3; the support rod 2 is provided with a water guide plate 14 inclined downward and inward, and both ends of the water guide plate 14 are provided with connecting plates 15 connected to the support rod 2, and the top of the base 1 is provided with a water collection chamber 16 for collecting waste water.

[0035] Figure 1 The clamping drive mechanism is not shown in FIG. Figure 2 It is reflected separately in

[0036] like Figure 2 As shown, the clamping drive mechanism includes a first bidirectional screw rod 10, which is installed in the mounting hole of the square frame support frame 29 through a bearing, one end of the first bidirectional screw rod 10 is connected to the motor shaft of the first motor 6, and the bottom of the first motor 6 is connected to the square frame support frame 29 through a support plate, and the thread of the first bidirectional screw rod 10 is connected to the first threaded sleeve 11 and the second threaded sleeve 12, and the first threaded sleeve 11 and the second threaded sleeve 12 are respectively connected to a clamping plate 4, and the first threaded sleeve 11 and the second threaded sleeve 12 also enable the two clamping plates 4 to clamp or release the test tube through reverse or opposite movements.

[0037] The clamping drive mechanism includes a second bidirectional screw rod 25, which is installed in the mounting hole of the square frame support frame 29 through a bearing. One end of the second bidirectional screw rod 25 is connected to the motor shaft of the second motor 7. The bottom of the second motor 7 is connected to the square frame support frame 29 through a support plate. The thread of the second bidirectional screw rod 25 is connected to the third threaded sleeve 23 and the fourth threaded sleeve 24. The third threaded sleeve 23 and the fourth threaded sleeve 24 are respectively connected to a clamping plate 4. The third threaded sleeve 23 and the fourth threaded sleeve 24 also enable the two clamping plates 4 to clamp or release the test tube through reverse or opposite movement; the first bidirectional screw rod 10 and the second bidirectional screw rod 25 are located on both sides of the clamping plate and work synchronously.

[0038] The two clamping plates 4 are both provided with clamping holes 5, and the two clamping holes 5 cooperate with each other to clamp the test tube. The two clamping plates 4 are close to each other, so that the clamping holes 5 on the two clamping plates 4 can clamp the test tube, and multiple test tubes can be clamped and fixed at the same time, which is convenient for fixing the test tubes, and test tubes of different diameters can also be clamped in pairs, thereby improving the applicability of test tube fixing and clamping.

[0039] The semicircular inner wall on one side of the clamping hole 5 is made of a stretchable elastic material, and a pressure sensor 9 is provided on the semicircular inner wall on the other side. The output value of the pressure sensor 9 is sent to the control unit, and the control unit determines whether the test tube is clamped or too tight.

[0040] like Figure 2 and Figure 3As shown, it further includes a rotating mechanism for pouring the sewage in the test tube. The rotating mechanism includes a first magnetic adsorbent 13, two support plates 3, a first rotating shaft 27, a second rotating shaft 28, and an electromagnet 31. Both ends of the square frame support 29 are respectively connected to the first rotating shaft 27 and the second rotating shaft 28. The first rotating shaft 27 is connected to the mounting hole of a support plate 3 through bearing A, and the second rotating shaft 28 is connected to the mounting hole of the other support plate 3 through bearing B. The first rotating shaft 27 and the second rotating shaft 28 are coaxial, so that the square frame support 29 can rotate; the other end of the first bidirectional lead screw 10 is provided with a first magnetic adsorbent 13, and an electromagnet 31 is provided above and / or below the first magnetic adsorbent 13. When the pressure value output by the pressure sensor 9 indicates that the test tube is clamped, the control unit controls the electromagnet 31 to be energized, and the first magnetic adsorbent 13 is adsorbed by the electromagnet 31, and the square frame support 29 and the test tube thereon are tilted to pour out the wastewater.

[0041] The first rotating shaft 27 is perpendicular to both the first bidirectional lead screw 10 and the second bidirectional lead screw 25. The second rotating shaft 28 is perpendicular to both the first bidirectional lead screw 10 and the second bidirectional lead screw 25.

[0042] There are two electromagnets 31, one is located above the first magnetic adsorbent 13, and the other is located below the first magnetic adsorbent 13. The distances between the two first magnetic adsorbents 13 and the electromagnets 31 are different. The electromagnet 31 with a longer distance can make the angle between the square frame support 29 and the horizontal plane larger, so that more wastewater is poured out of the test tube, and the electromagnet 31 with a shorter distance can make the angle between the square frame support 29 and the horizontal plane smaller, so that less wastewater is poured out of the test tube.

[0043] In addition, two sets of rotating mechanisms can be set up, one for the first bidirectional lead screw 10 and the other for the second bidirectional lead screw 25. Therefore, a second magnetic adsorbent 26 needs to be set on the second bidirectional lead screw 25. The synchronous operation of the two sets can make the rotation more stable.

[0044] As Figure 5 As shown, the lowest end of the water guide plate 14 is provided with a water collecting plate 17 that inclines inward. Both ends of the water collecting plate 17 are provided with water baffle plates 18 connected to the support rod 2; the bottom end of the base 1 is provided with a drainage hopper 19 that inclines downward. The bottom end of the drainage hopper 19 is provided with a drain pipe 20, a control valve 21 is provided on the drain pipe 20, and the bottom end of the base 1 is provided with support legs 22. When the wastewater in the test tube is poured out, under the guiding action of the water guide plate 14 and the water collecting plate 17, the wastewater enters the water collecting cavity 16 opened on the base 1. By opening the control valve 21, the wastewater inside the water collecting cavity 16 can be discharged from the drain pipe 20.

[0045] The control principle of the automatic solid-phase extraction equipment of the present invention is as follows:

[0046] Step 1: When the test tube clamping mechanism moves the lower end of the test tube to the clamping hole 5, the control unit controls the first motor 6 and the second motor 7 to work synchronously, so that the two clamping plates 4 move towards each other and gradually approach the lower end of the test tube;

[0047] Step 2: After the two clamping plates 4 clamp the lower end of the test tube, the pressure sensor 9 starts to send the pressure value to the control unit. When the pressure value reaches A, the test tube clamping mechanism completely releases the test tube and moves it away;

[0048] Step 3: When the pressure value output by the pressure sensor 9 reaches B, B > A, the control unit controls the first motor 6 and the second motor 7 to stop working, indicating that the test tube is clamped; One side of the inner wall of the semi-circle of the clamping hole 5 is made of a telescopic elastic material, so that the test tube can be further clamped after being clamped without damaging the test tube.

[0049] Step 4: The control unit activates the electromagnet 31, so that the first magnetic attachment 13 on the first bidirectional lead screw 10 is adsorbed, and at the same time drives the two clamping plates 4 and the test tube to rotate and tilt to pour out the waste water.

[0050] After Step 3, the waste water in the test tube is located in the upper layer and the solution is located in the lower layer; The image acquisition device acquires a picture of the height of the waste water in the test tube and sends it to the control unit. The control unit determines to activate different electromagnets according to the height of the waste water. The distances between the two first magnetic attachments 13 and the electromagnet 31 are different. The electromagnet 31 with a longer distance can make the angle between the square support frame 29 and the horizontal plane larger, so that more waste water can be poured out of the test tube. The electromagnet 31 with a shorter distance can make the angle between the square support frame 29 and the horizontal plane smaller, so that less waste water can be poured out of the test tube.

[0051] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the implementation of the present invention is not limited by the above-mentioned manner. As long as various improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. An automatic solid-phase extraction device, comprising a base (1), characterized in that: There are two clamping plates (4) provided on the base (1). Under the action of the clamping drive mechanism, the two clamping plates can move towards each other to clamp the test tube, and can also move in the reverse direction to release the test tube; the clamping plate (4) clamping the test tube can be tilted under the action of the rotating mechanism, so that the waste water inside the test tube can be poured out obliquely. The clamping drive mechanism includes a first bidirectional lead screw (10). The first bidirectional lead screw (10) is installed in the mounting hole of the square support frame (29) through a bearing. One end of the first bidirectional lead screw (10) is connected to the motor shaft of the first motor (6). The bottom of the first motor (6) is connected to the square support frame (29) through a support plate. The threads of the first bidirectional lead screw (10) are connected to a first thread sliding sleeve (11) and a second thread sliding sleeve (12). The first thread sliding sleeve (11) and the second thread sliding sleeve (12) are respectively connected to a clamping plate (4). The first thread sliding sleeve (11) and the second thread sliding sleeve (12) also make the two clamping plates (4) clamp or release the test tube through reverse or opposite movement. The clamping drive mechanism includes a second bidirectional lead screw (25). The second bidirectional lead screw (25) is installed in the mounting hole of the square support frame (29) through a bearing. One end of the second bidirectional lead screw (25) is connected to the motor shaft of the second motor (7). The bottom of the second motor (7) is connected to the square support frame (29) through a support plate. The threads of the second bidirectional lead screw (25) are connected to a third thread sliding sleeve (23) and a fourth thread sliding sleeve (24). The third thread sliding sleeve (23) and the fourth thread sliding sleeve (24) are respectively connected to a clamping plate (4). The third thread sliding sleeve (23) and the fourth thread sliding sleeve (24) also make the two clamping plates (4) clamp or release the test tube through reverse or opposite movement. The first bidirectional lead screw (10) and the second bidirectional lead screw (25) are located on both sides of the clamping plate and work synchronously. Both of the two clamping plates (4) are provided with clamping holes (5). The two clamping holes (5) cooperate with each other to clamp the test tube. One side of the inner wall of the semi-circle of the clamping hole (5) is made of stretchable elastic material, and a pressure sensor (9) is provided on the inner wall of the other semi-circle. The output value of the pressure sensor (9) is sent to the control unit, and the control unit thereby judges whether the test tube is clamped or clamped too tightly. It also includes a rotating mechanism for pouring the sewage in the test tube. The rotating mechanism includes a first magnetic attachment (13), two support plates (3), a first rotating shaft (27), a second rotating shaft (28), and an electromagnet (31). Both ends of the square frame support (29) are respectively connected to the first rotating shaft (27) and the second rotating shaft (28). The first rotating shaft (27) is connected to the mounting hole of a support plate (3) through bearing A, and the second rotating shaft (28) is connected to the mounting hole of the other support plate (3) through bearing B. The first rotating shaft (27) and the second rotating shaft (28) are coaxial so that the square frame support (29) can rotate. The other end of the first bidirectional lead screw (10) is provided with a first magnetic attachment (13). An electromagnet (31) is provided above and / or below the first magnetic attachment (13). When the pressure value output by the pressure sensor (9) indicates that the test tube is clamped, the control unit controls the electromagnet (31) to be energized, and the first magnetic attachment (13) is adsorbed by the electromagnet (31), and the square frame support (29) and the test tube thereon tilt to pour out the wastewater. There are two electromagnets (31). One is located above the first magnetic attachment (13), and the other is located below the first magnetic attachment (13). The distances between the two first magnetic attachments (13) and the electromagnets (31) are different. The electromagnet (31) with a longer distance can make the angle between the square frame support (29) and the horizontal plane larger, so that more wastewater can be poured out of the test tube. The electromagnet (31) with a shorter distance can make the angle between the square frame support (29) and the horizontal plane smaller, so that less wastewater can be poured out of the test tube. The wastewater in the test tube is located in the upper layer, and the solution is located in the lower layer. The image acquisition device collects pictures of the height of the wastewater in the test tube and sends them to the control unit. The control unit determines which electromagnet to activate according to the height of the wastewater. The distances between the two first magnetic attachments (13) and the electromagnets (31) are different. The electromagnet (31) with a longer distance can make the angle between the square frame support (29) and the horizontal plane larger, so that more wastewater can be poured out of the test tube. The electromagnet (31) with a shorter distance can make the angle between the square frame support (29) and the horizontal plane smaller, so that less wastewater can be poured out of the test tube.

2. The automatic solid-phase extraction device according to claim 1, characterized in that: It also includes multiple support rods (2). One end of the support rod (2) is connected to a support plate (3). The support rod (2) is provided with a water guide plate (14) that inclines downward and inward. Both ends of the water guide plate (14) are provided with connecting plates (15) connected to the support rod (2). The top end of the base (1) is provided with a water collection cavity (16) for collecting wastewater. The lowest end of the water guide plate (14) is provided with a water collection plate (17) that inclines inward. Both ends of the water collection plate (17) are provided with water baffle plates (18) connected to the support rod (2). The bottom end of the base (1) is provided with a drainage hopper (19) that inclines downward. The bottom end of the drainage hopper (19) is provided with a drain pipe (20). A control valve (21) is provided on the drain pipe (20). The bottom end of the base (1) is provided with support legs (22).

3. A control method for the automatic solid-phase extraction device according to claim 1 or 2, comprising the following steps: Step 1: When the test tube clamping mechanism moves the lower end of the test tube to the clamping hole (5), the control unit controls the first motor (6) and the second motor (7) to work synchronously, so that the two clamping plates (4) move towards each other and gradually approach the lower end of the test tube; Step 2: After the two clamping plates (4) clamp the lower end of the test tube, the pressure sensor (9) starts to send the pressure value to the control unit. When the pressure value reaches A, the test tube clamping mechanism completely releases the test tube and moves it away; Step 3: When the pressure value output by the pressure sensor (9) reaches B, B > A, the control unit controls the first motor (6) and the second motor (7) to stop working, indicating that the test tube is clamped; Step 4: The control unit activates the electromagnet (31), so that the first magnetic attachment (13) on the first bidirectional lead screw (10) is adsorbed, and at the same time drives the two clamping plates (4) and the test tube to rotate and tilt to pour out the wastewater; The wastewater in the test tube is located in the upper layer and the solution is located in the lower layer; the image acquisition device acquires a picture of the height of the wastewater in the test tube and sends it to the control unit. The control unit determines to activate different electromagnets according to the height of the wastewater. The distances between the two first magnetic attachments (13) and the electromagnet (31) are different. The electromagnet (31) with a longer distance can make the angle between the square support frame (29) and the horizontal plane larger, so that more wastewater is poured out of the test tube, and the electromagnet (31) with a shorter distance can make the angle between the square support frame (29) and the horizontal plane smaller, so that less wastewater is poured out of the test tube.

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