A capillary electrophoresis system and method of use for rapid detection of inorganic explosives

Abstract

The application discloses a capillary electrophoresis system for rapidly detecting inorganic explosives, which comprises an automatic sampling unit and a detection pool connected. The system has the advantages of simple structure, convenient operation, high practicability, automatic sampling, reduced influence of Joule heat in capillary electrophoresis, short separation time and remarkable separation effect. The application further discloses a use method of the capillary electrophoresis system for rapidly detecting inorganic explosives.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of capillary electrophoresis, in particular to a capillary electrophoresis system for rapid detection of inorganic explosives and a use method thereof. BACKGROUND

[0002] Capillary electrophoresis (CE) is a general separation and analysis technique, which can be used to separate and analyze substances from high molecular weight to low molecular weight. It has the advantages of high efficiency, rapidity, small injection volume, low solvent consumption and simple sample pretreatment. In general, a capillary with a length of 30-60 cm and an inner diameter of 50-100 μm is used in CE, and the separation voltage is generally less than 500 V / cm. The analysis time is generally 5-30 min, but this time still cannot meet the analysis requirements in many cases, such as rapid detection of explosives, analysis of short-lived substances, monitoring of biochemical reaction processes, etc. High-speed capillary electrophoresis uses a thin inner diameter and a short capillary to achieve high-speed separation, which can achieve true high efficiency and high speed. In addition to maintaining the original advantages of CE, the analysis time is shortened to a few minutes or even a few seconds, so it is an analysis technique that can meet the requirements of modern analysis and has development potential. When high-speed capillary electrophoresis uses a short capillary to achieve high-speed separation, the separation field strength on the capillary can reach several thousand volts per centimeter, which will generate a lot of heat. Therefore, how to achieve rapid injection and how to effectively cool the capillary to reduce the influence of Joule heat are key problems for the further development of rapid electrophoresis. SUMMARY

[0003] The purpose of the present application is to solve the problems of slow injection speed and serious Joule heat in the prior art, and to provide a capillary electrophoresis system for rapid detection of inorganic explosives and a use method thereof. This system has the advantages of simple structure, easy operation, strong practicability, automatic injection, reduced influence of Joule heat in capillary electrophoresis, short separation time and remarkable separation effect.

[0004] The technical solution for achieving the purpose of the present application is as follows:

[0005] A capillary electrophoresis system for rapid detection of inorganic explosives, comprising an automatic injection unit and a detection cell connected,

[0006] The automatic injection unit comprises a motor with a control line and a rotating shaft facing upward, a gear that can rotate horizontally is arranged at the upper end of the rotating shaft, a bracket with a rack groove is arranged on one side of the motor, a movable support block with a 7-shaped rack is arranged on the bracket, the rack of the support block is engaged with the gear, and a first buffer solution storage bottle with a high-voltage end lead line and a high-voltage end electrode and a sample storage bottle are arranged side by side at the extended end of the support block,

[0007] The detection pool is provided with a capillary tube axially penetrating the detection pool, the left end of the capillary tube is close to the first buffer solution storage bottle, the right end is close to the second buffer solution storage bottle with the top ground electrode and ground wire, the bottom surface of the detection pool close to the left end of the capillary tube is provided with a cooling oil outlet, and the bottom surface close to the right end of the capillary tube is provided with a first detection signal line, a second detection signal line and a cooling oil inlet in turn from the right end of the capillary tube to the left end of the capillary tube,

[0008] The cooling oil inlet and the cooling oil outlet are connected with a temperature control unit, the first detection signal line and the second detection signal line are connected with a detector, and the high-voltage wire, the ground wire and the motor control wire are connected with a control unit.

[0009] The detection pool is formed by stereolithography technology, and the detection pool comprises two electrode cavities, a shielding layer cavity and a cooling liquid channel, after the capillary tube is inserted into the detection pool, a low-melting-point metal is poured into the detection pool through the hole of the low-melting-point metal, so as to form two electrodes and a shielding layer, the two electrodes are a receiving electrode and an excitation electrode, the receiving electrode is connected with the first detection signal line, the excitation electrode is connected with the second detection signal line, the cooling liquid channel is in communication with the cooling oil inlet and the cooling oil outlet at two ends, the capillary tube is arranged in the cooling liquid channel, and an oil seal cavity is arranged in the detection pool close to the left end of the capillary tube, so as to prevent the cooling oil from leaking.

[0010] The temperature control unit comprises a semiconductor refrigeration sheet, a heat conduction block, a cooling fan, a peristaltic pump, the peristaltic pump pumps the cooling oil into the detection pool through the cooling oil inlet through a silicone tube connected with a heat-conducting copper tube, the heat-conducting copper tube is tightly wound on the heat conduction block, the insulating cooling oil is arranged in a small-capacity centrifugal tube, and the insulating cooling oil is circulated through the heat conduction block by the peristaltic pump and flows into the detection pool.

[0011] The control unit comprises an Arduino UNO microcontroller, a serial screen and a control circuit, the serial screen sends instructions to the Arduino UNO microcontroller as an upper computer, the Arduino UNO microcontroller sends signals to control the motor and the control circuit as a lower computer, the Arduino UNO microcontroller sends signals to turn on and off high-voltage electricity and adjust the size of the high-voltage value, and the control circuit comprises a high-voltage power supply and a relay for turning on and off high-voltage electricity.

[0012] The first buffer solution storage bottle, the sample storage bottle and the second buffer solution storage bottle are all provided with notches, and the capillary tube extends into the first buffer solution storage bottle, the sample storage bottle and the second buffer solution storage bottle through the notches.

[0013] The detector is a non-contact conductivity detector.

[0014] The application relates to a method for using a capillary electrophoresis system for rapidly detecting inorganic explosives, and the method comprises the following steps:

[0015] 1) first, a capillary is flushed with NaOH, HCl and ultrapure water in sequence, then Bis-Tris / MOPS buffer solutions are filled into a first buffer solution storage bottle and a second buffer solution storage bottle, a sample solution is filled into a sample storage bottle, the capillary is inserted into a detection cell, the right end of the capillary is always inserted into the second buffer solution storage bottle through a notch, and the left end of the capillary is arranged at the center of the notch of the first buffer solution storage bottle;

[0016] 2) the sample storage bottle is adjusted so that the notch of the sample storage bottle is on the same horizontal plane as the notch of the first buffer solution storage bottle, the system is run once in a manual feeding mode, normalness of each component is determined, and the system is switched to an automatic mode, wherein the manual feeding mode is as follows: a forward running button on a serial port screen is clicked, a gear is rotated counterclockwise by a motor, a rack of a supporting block moves along with the gear, the left end of the capillary is inserted into the sample storage bottle, 10 is input at an input high voltage s, that is, the sample feeding high voltage is 10 kV, the high voltage s button is clicked to start the sample feeding high voltage, the sample feeding high voltage is kept for 3 s, the high voltage s button is clicked again to turn off the sample feeding high voltage, the reverse running button is clicked, the gear is rotated clockwise, the rack of the supporting block moves reversely, 10 is input at an input high voltage b, that is, the separation high voltage is 10 kV, the high voltage b button is clicked to start the separation high voltage, the separation high voltage is kept for 90 s, and the high voltage b button is clicked again to turn off the separation high voltage, that is, one separation in the manual mode is completed;

[0017] in the automatic mode, after the sample feeding time, the pressurizing time, the input voltage b and the input voltage s are set, the running button is clicked, and data processing is performed after separation is completed.

[0018] The motor is a stepping motor.

[0019] The capillary is a quartz capillary.

[0020] During work, a complete electrophoresis loop is formed between the high-voltage end electrode and the ground end electrode.

[0021] Compared with the prior art, the technical scheme is detected by a non-contact conductivity detection method of a self-made conductivity detection cell, temperature control is realized by a temperature control unit, automatic sample feeding is realized by controlling a motor, and data acquisition, analysis and processing can be realized in real time and quickly.

[0022] According to the change of the solution conductivity in the capillary, the conductivity detector detects the conductivity change to obtain the signal peak of different ions, and the migration time of the signal peak is used to determine the type of the to-be-detected substance, and the signal peak height or area is used to determine the content of the to-be-detected substance.

[0023] The system has simple structure, easy operation, strong practicability, automatic sample injection, reduced influence of Joule heat in capillary electrophoresis, short separation time and remarkable separation effect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A structure schematic diagram of an embodiment is shown in the figure.

[0025] Figure 2 A structure schematic diagram of an automatic sample injection unit in an embodiment is shown in the figure.

[0026] Figure 3 A sectional view of a detection cell in an embodiment is shown in the figure.

[0027] Figure 4 A control interface schematic diagram of a serial port screen in an embodiment is shown in the figure.

[0028] Figure 5 A volt-ampere curve schematic diagram at different temperatures in an embodiment is shown in the figure.

[0029] Figure 6 A comparison diagram of cation sample separation electrophoresis at different temperatures in an embodiment is shown in the figure.

[0030] Figure 7 An anion separation electrophoresis diagram in an embodiment is shown in the figure.

[0031] In the figure, 1. Gear 2. Support 3. Support block 4. High-voltage end wire 5. High-voltage end electrode 6. First buffer solution storage bottle 7. Capillary 8. Detection cell 9. Ground electrode 10. Ground end wire 11. Second buffer solution storage bottle 12. First detection signal line 13. Second detection signal line 14. Cooling oil inlet 15. Cooling oil outlet 16. Sample storage bottle 17. Motor 19. Hole for injecting low-melting-point metal 20. Shielding layer 21. Oil sealing cavity 22. Electrode 23. Cooling oil channel. DETAILED DESCRIPTION

[0032] The invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but is not limited to the invention.

[0033] Embodiment:

[0034] The reagents used in the experiment are analytical pure or above, and all solutions are prepared with ultrapure water. The background electrolyte includes bis(2-hydroxyethyl) imino tris(hydroxymethyl) methane / 3-morpholine propanesulfonic acid (BIS-TRIS / MOPS), and the chloride metal salt is dissolved in ultrapure water to prepare a stock solution with a concentration of 2 mmol / L. When used, it is diluted to the required concentration in stages.

[0035] Referring to Figure 1 A capillary electrophoresis system for rapid detection of inorganic explosives includes an automatic sampling unit and a detection cell connected,

[0036] As Figure 2 shown, the automatic sampling unit includes a motor 17 with a control line and an upward rotating shaft, the upper end of the rotating shaft is provided with a horizontally rotatable gear 1, one side of the motor 17 is provided with a bracket 2 with a rack groove, the bracket is provided with a rack-shaped support block 3 with a rack that moves in the rack groove of the bracket, the rack of the support block 3 is engaged with the gear 1, the extending end of the support block 3 is provided with a first buffer solution storage bottle 6 and a sample storage bottle 16 in parallel, the first buffer solution storage bottle 6 is provided with a high-voltage end lead 4 and a high-voltage end electrode 5,

[0037] As Figure 3 shown, the detection cell 8 is provided with a capillary 7 axially passing through the detection cell 8, the left end of the capillary 7 is close to the first buffer solution storage bottle 6, the right end is close to the second buffer solution storage bottle 11 with the top ground end electrode 9 and the ground end lead 10, the bottom surface of the detection cell 8 close to the left end of the capillary 7 is provided with a cooling oil outlet 15, and the bottom surface close to the right end of the capillary 7 is provided with a first detection signal line 12, a second detection signal line 13 and a cooling oil inlet 14 in turn from the right end of the capillary to the left end of the capillary,

[0038] The cooling oil inlet 14 and the cooling oil outlet 15 are connected with a temperature control unit, the first detection signal line 12 and the second detection signal line 13 are connected with a detector, and the high-voltage end lead 4, the ground end lead 10 and the motor control line are connected with a control unit.

[0039] The detection cell 8 is integrally printed by stereolithography technology, and the detection cell 8 includes two electrode cavities, a shielding layer cavity and a cooling liquid channel 23. After the capillary 7 is inserted into the detection cell 8, low melting point metal is poured into the low melting point metal through the hole 19 in the detection cell to form two electrodes 22 and a shielding layer 20. The two electrodes 22 are receiving electrodes and excitation electrodes, wherein the receiving electrodes are connected with the first detection signal line 12, and the excitation electrodes are connected with the second detection signal line 13. The cooling liquid channel 23 is in communication with the cooling oil inlet 14 and the cooling oil outlet 15 at both ends, and the capillary 7 is arranged in the cooling liquid channel 23. An oil seal cavity 21 is arranged in the detection cell close to the left end of the cooling liquid channel 23 to prevent the cooling oil from leaking.

[0040] The temperature control unit includes a semiconductor refrigeration sheet, a cold conducting block, a heat dissipation fan, and a peristaltic pump.

[0041] The control unit includes an Arduino UNO microcontroller, a serial screen, and a control circuit. Figure 4 As shown in the figure, the serial screen sends instructions to the Arduino UNO microcontroller as the upper computer, and the Arduino UNO microcontroller sends signals to control the motor and the control circuit as the lower computer.

[0042] The first buffer solution storage bottle 6, the sample storage bottle 16, and the second buffer solution storage bottle 11 are each provided with a notch, and the capillary 7 extends into the first buffer solution storage bottle 6, the sample storage bottle 16, and the second buffer solution storage bottle 11 through the notch.

[0043] The detector is a non-contact conductivity detector, and in this example, the detector is a TraceDec conductivity detector.

[0044] The motor 17 is a stepper motor.

[0045] The capillary 7 is a quartz capillary.

[0046] During operation, a complete electrophoresis loop is formed between the high-voltage electrode 5 and the ground electrode 9.

[0047] A method for using the capillary electrophoresis system for rapid detection of inorganic explosives includes the capillary electrophoresis system for rapid detection of inorganic explosives.

[0048] 1) First, rinse the capillary 7 with 1 mol / L NaOH, 1 mol / L HCl and ultrapure water for 10 min in turn, then fill the first buffer solution reservoir 6 and the second buffer solution reservoir 11 with Bis-Tris / MOPS buffer solution, 1 mL of Bis-Tris / MOPS buffer solution is filled in the first buffer solution reservoir 6, 1.5 mL of Bis-Tris / MOPS buffer solution is filled in the second buffer solution reservoir 11, fill the sample reservoir 16 with sample solution, insert the capillary 7 into the detection cell 8, the right end of the capillary is always inserted into the second buffer solution reservoir 11 through the slot, and the left end of the capillary is placed in the center of the slot of the first buffer solution reservoir 6;

[0049] 2) Adjust the sample reservoir 16 so that the slot of the sample reservoir is at the same level as the slot of the first buffer solution reservoir, run the system once in manual mode to determine that all components are normal, then switch to automatic mode, the manual mode is as follows: click the forward running button on the serial port screen, the motor 17 drives the gear 1 to rotate counterclockwise, the rack of the support block moves with the gear 1, so that the left end of the capillary is immersed in the sample reservoir 16, input 10 at the input high voltage s, i.e. the sample injection high voltage is 10 kV, click the high voltage s button to start the sample injection high voltage, stay for 3 s, then click the high voltage s button to turn off the sample injection high voltage; click the reverse running, the gear 1 rotates clockwise, the rack of the support block moves in the opposite direction, input 10 at the input high voltage b, i.e. the separation high voltage is 10 kV, click the high voltage b button to start the separation high voltage, stay for 90 s, then click the high voltage b button to turn off the separation high voltage, i.e. one separation in manual mode is completed;

[0050] In automatic mode, set the sample injection time, pressurization time, input voltage b and input voltage s, then click run to wait for the separation to be completed before data processing.

[0051] Determination of voltammetry curve:

[0052] The capillary 7 used in this example has an inner diameter of 50 μm, an outer diameter of 360 μm and a length of 8.7 cm. During the electrophoresis process, the current in the electrophoresis loop is measured with and without circulating cooling oil outside the capillary. When measuring the current, the buffer solution used is 300 mM Bis-Tris / MOPS and 2 mM 18-crown-6; high concentration BGE can generate more Joule heat, so effective heat dissipation or temperature control of the capillary is required. Under temperature control, the voltammetry curve is plotted according to the measured current and the field strength on the capillary 7 as shown in Figure 5 Figure 5 ​It can be judged that the current in the electrophoresis circuit is much smaller than that without cooling oil under the same field strength and with circulating cooling oil outside the capillary, which proves that the circulating cooling oil can effectively take away the Joule heat generated in the electrophoresis process. 2 , the current I = GV, where G is the conductivity of the electrolyte and V is the voltage; therefore P = IV, and the heating power P is proportional to I at the same voltage; the current can be reduced by up to 52% when the temperature of the insulating cooling oil is controlled at 2 ℃, and by up to 53% when the temperature is controlled at -6 ℃. In order to reduce energy consumption, the temperature of the insulating cooling oil was controlled at 2 ℃ in the subsequent experiments.

[0053] Sample separation at different temperatures:

[0054] The capillary 7 used in this example has an inner diameter of 25 μm, an outer diameter of 360 μm, and a length of 8.5 cm; before use, the quartz capillary was sequentially washed with 1 mol / L NaOH, 1 mol / L HCl and ultrapure water for 10 min each; the injection voltage was 2 kV, the separation voltage was 10 kV, the injection time was set to 0 s, and the separation time was set to 1 min. The background buffer used was 300 mM Bis-Tris / MOPS and 2 mM 18-crown-6-ether, and the sample solution used was a mixed solution of 200 μM NH4 + , K + , Na + , Li + , Ca 2+ , and Mg 2+ . Figure 6 The dashed line in the figure indicates sample separation at room temperature; NH4 + and K + are not completely separated. Figure 6 The solid line in the figure indicates sample separation of the capillary in 2 ℃ cooling oil; NH4 + and K + are completely separated, and the baseline is more stable, which proves that the circulating cooling oil can improve the separation effect.

[0055] Separation and analysis of inorganic explosives:

[0056] The capillary 7 used in this example has an inner diameter of 10 μm, an outer diameter of 360 μm, and a length of 15.5 cm. Before use, the capillary was sequentially washed with 1 mol / L NaOH, 1 mol / L HCl and ultrapure water for 10 min each, then washed with 5% (w / v) HDMB solution for 5 min to make the inner wall of the capillary positively charged to obtain electroosmotic flow, and finally washed with background buffer solution for 60 min to stabilize the electroosmotic flow. The injection voltage was -1 kV, the separation voltage was -10 kV, the injection time was set to 0 s, and the separation time was set to 3 min. The background buffer used was 40 mM Tris / CHES and 0.8% (w / v) PEI (MW 600), and the sample solution used was a mixed solution of 200 μM CIO4 - , NO3 - , SO4 2- , SCN - , CIO3 - , N3 - and 400 μM MSA - , PO4 3- . Figure 7 The electropherogram of the anion mixed sample is shown in Figure 1. Among them, CO3 2- may be CO2 from the air rapidly dissolved in the sample solution and the buffer solution; CIO3 - , N3 - , CIO4 - , NO3 - are four common explosive tracer ions, SO4 2- , SCN - , PO4 3- are common background ions; it can be seen from Figure 7 that the system can accurately detect explosives.

Claims

1. A method of using a capillary electrophoresis system for rapid detection of inorganic explosives, comprising: The system comprises a connected automatic sampling unit and a detection cell, The automatic sampling unit comprises a motor with a control line and an upward rotating shaft, the upper end of the rotating shaft is provided with a horizontally rotatable gear, one side of the motor is provided with a bracket with a rack groove, the bracket is provided with a movable rack-shaped support block with a 7-shaped tooth, the rack of the support block is engaged with the gear, the extending end of the support block is provided with a first buffer solution storage bottle and a sample storage bottle in parallel, both of which have high-voltage end lead wires and high-voltage end electrodes on the top, The detection cell is provided with a capillary tube axially passing through the detection cell, the left end of the capillary tube is close to the first buffer solution storage bottle, the right end of the capillary tube is close to the second buffer solution storage bottle with the ground end electrode and the ground end lead wire on the top, the bottom surface of the detection cell close to the left end of the capillary tube is provided with a cooling oil outlet, and the bottom surface close to the right end of the capillary tube is provided with a first detection signal line, a second detection signal line and a cooling oil inlet in sequence from the right end of the capillary tube to the left end of the capillary tube, The cooling oil inlet and the cooling oil outlet are connected with a temperature control unit, the first detection signal line and the second detection signal line are connected with a detector, and the high-voltage end lead wire, the ground end lead wire and the motor control line are connected with a control unit; The detection cell is integrally printed by stereolithography technology, the detection cell comprises two electrode cavities, a shielding layer cavity and a cooling liquid channel, after the capillary tube is inserted into the detection cell, a low-melting-point metal is poured into the hole in the detection cell to form two electrodes and a shielding layer, the two electrodes are a receiving electrode and an excitation electrode, wherein the receiving electrode is connected with the first detection signal line, the excitation electrode is connected with the second detection signal line, the cooling liquid channel is in communication with the cooling oil inlet and the cooling oil outlet at both ends, and the capillary tube is arranged in the cooling liquid channel; The first buffer solution storage bottle, the sample storage bottle and the second buffer solution storage bottle are all provided with a notch, and the capillary tube extends into the first buffer solution storage bottle, the sample storage bottle and the second buffer solution storage bottle through the notch; The use method comprises the following steps: 1) first, flush the capillary tube with NaOH, HCl and ultrapure water in sequence, then fill the first buffer solution storage bottle and the second buffer solution storage bottle with Bis-Tris / MOPS buffer solution, fill the sample storage bottle with sample solution, insert the capillary tube into the detection cell, the right end of the capillary tube is always inserted into the second buffer solution storage bottle through the notch, and the left end of the capillary tube is arranged at the center of the notch of the first buffer solution storage bottle; 2) Adjust the sample reservoir bottle so that the notch of the sample reservoir bottle is at the same level as the notch of the first buffer solution reservoir bottle. Run the system once in manual mode to ensure that all components are working properly, and then switch to automatic mode. In manual mode, click the forward run button on the serial screen to rotate the gear counterclockwise, and the rack of the support block moves with the gear to immerse the left end of the capillary in the sample reservoir bottle. Enter 10 at input high voltage s, which is the sample injection high voltage, click the high voltage s button to start the sample injection high voltage, and then click the high voltage s button again to turn off the sample injection high voltage. Click the reverse run button to rotate the gear clockwise, and the rack of the support block moves in the opposite direction. Enter 10 at input high voltage b, which is the separation high voltage, click the high voltage b button to start the separation high voltage, and then click the high voltage b button again to turn off the separation high voltage. This completes one separation in manual mode. In automatic mode, set the sample injection time, pressurization time, input high voltage b, and input high voltage s, and then click run to wait for the separation to complete before performing data processing.

2. The method of using the capillary electrophoresis system for rapid detection of inorganic explosives according to claim 1, wherein, The temperature control unit includes a semiconductor refrigeration sheet, a heat dissipation block, a cooling fan, and a peristaltic pump. The peristaltic pump pumps the insulating cooling oil into the detection pool through the silicone tube connected to the heat dissipation copper pipe. The heat dissipation copper pipe is tightly wound around the heat dissipation block, and the insulating cooling oil is placed in a small volume centrifuge tube. The peristaltic pump circulates the insulating cooling oil through the heat dissipation block and into the detection pool.

3. The method of using the capillary electrophoresis system for rapid detection of inorganic explosives according to claim 1, wherein, The control unit includes an Arduino UNO microcontroller, a serial screen, and a control circuit. The serial screen sends instructions to the Arduino UNO microcontroller as the upper computer, and the Arduino UNO microcontroller sends signals to control the motor and control circuit as the lower computer. The Arduino UNO microcontroller sends signals to turn on and off the high voltage and adjust the high voltage value. The control circuit includes a high voltage power supply and a relay for turning on and off the high voltage.

4. The method of using the capillary electrophoresis system for rapid detection of inorganic explosives according to claim 1, wherein, The detector is a non-contact conductivity detector.

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