Gas sampling calibration mechanism for gas chromatography

Abstract

The present invention relates to the field of gas chromatographs, and discloses a gas chromatography gas sample introduction calibration mechanism, which comprises: a calibration tube, one end of which is open, and the inner wall of the other end of which is provided with a first elastic member and a distance measurement sensor; a first gas outlet of the three-way valve is connected with the open end of the calibration tube, a second gas outlet is connected with a gas inlet tube and communicated with the chromatographic column, and the gas inlet is connected with a sample injection tube. In the invention, by adopting a mode that the main piston directly pushes the sample gas, the initial position of the main piston directly abuts against the gas outlet of the three-way valve, the first elastic piece pushes the main piston to reset after calibration is completed, the sample gas is pressed into the chromatographic column without an intermediate link, and the sample gas mixing caused by the fact that the dead volume is filled with the pushed gas in advance is avoided; and when the main piston resets to push the sample gas, the cleaning head slides in a manner of clinging to the inner wall of the calibration tube, so that residues on the tube wall are physically scraped and cleaned.

Description

Technical Field

[0001] The invention relates to the field of gas chromatographs, and in particular to a gas sampling calibration mechanism for gas chromatography. Background Art

[0002] As a core instrument for gas composition analysis, the accuracy of the gas chromatograph's sampling system directly impacts the reliability of test results. In vehicle-mounted mobile chromatographs, real-time testing of sample gases in diverse environments (such as high and low temperatures, high pressure, and humid or dusty environments) is required. These samples are often unstable and have complex compositions, placing higher demands on sampling calibration technology.

[0003] Currently, gas injection calibration commonly uses a loop as a volume calibration element. Its operating principle is to pre-set the target volume using a loop, and then use a push gas (such as high-purity carrier gas or clean air) to push the sample gas within the loop into the chromatographic column. This method relies on the fixed volume of the loop for calibration, is relatively simple, and is low-cost, making it suitable for stable environments such as laboratories.

[0004] After searching, the publication number CN220084779U is a standard gas quantitative sampling device for a gas chromatograph, including a shell, the shell including a six-way valve chamber, a sample chamber fixedly installed on the top of one end of the six-way valve chamber, a sampling chamber fixedly installed on the top of the sample chamber, an electric six-way valve fixedly installed inside the six-way valve chamber, a quantitative sampling mechanism fixedly installed inside the sampling chamber, a carrier gas connector fixedly installed on the top of the other end of the six-way valve chamber, and a detection device connector fixedly installed on one side of the six-way valve chamber. This utility model can effectively perform quantitative sampling of samples and can effectively flush the quantitative sampling mechanism to avoid sample residue.

[0005] At present, during the sample pushing process of the gas injection calibration mechanism, there is an inevitable dead volume between the outlet of the quantitative loop and the inlet of the chromatographic column. The push gas needs to fill the dead volume first, resulting in a small amount of push gas mixing with the sample gas and entering the chromatographic column, interfering with the qualitative and quantitative analysis of the target components. At the same time, some sample gases contain polar compounds or high-boiling point components, which are easily attached to the inner wall of the pipeline through hydrogen bonds, van der Waals forces, etc., and the residue removal rate is low if it relies solely on push gas purging. As the number of injections increases, the residue accumulates on the inner wall of the pipeline to form an adsorption layer, resulting in chromatographic peak tailing, splitting and even baseline drift. Summary of the Invention

[0006] In order to solve the above-mentioned problems of sample dilution, residual contamination and poor environmental adaptability in the sample injection calibration of the vehicle-mounted mobile chromatograph, the present invention is achieved through the following technical solutions.

[0007] A gas sampling calibration mechanism for gas chromatography, comprising:

[0008] A calibration tube having an open end and an inner wall of the other end mounted with a first elastic member and a distance measuring sensor;

[0009] A three-way valve, wherein the first air outlet is connected to the open end of the calibration tube, the second air outlet is connected to the air inlet pipe and communicates with the chromatographic column, and the air inlet is connected to the sample injection tube;

[0010] A main piston is disposed in the calibration tube and initially abuts against the air outlet of the three-way valve. One end of the main piston is connected to the first elastic member, and the other end is provided with a cleaning head that contacts the inner wall of the calibration tube.

[0011] A limiting ring is axially movably disposed in the calibration tube and is used to limit the stroke of the main piston;

[0012] When the three-way valve is switched to connect the sample tube and the calibration tube, the sample gas pushes the main piston to compress the first elastic member, and the distance sensor detects the displacement of the main piston;

[0013] When the three-way valve is switched to connect the calibration tube with the air inlet pipe, the first elastic member releases its elastic force to push the main piston to reset, and the cleaning head scrapes the wall of the calibration tube and pushes the gas into the chromatographic column.

[0014] Preferably, the main piston comprises:

[0015] A cavity is provided in the main piston, and an end surface of the main piston facing the open end of the calibration tube is provided with a through hole communicating with the cavity;

[0016] a one-way valve, installed in the through hole;

[0017] An exhaust hole is provided on the inner wall of the cavity and passes through the top of the main piston;

[0018] A piston head is installed in the cavity, and the piston head is connected to the inner wall of the cavity through a second elastic member;

[0019] When the main piston moves to the limit ring, the continuously entering gas enters the cavity through the one-way valve and pushes the piston head to compress the second elastic member, so that the exhaust hole opens to discharge excess gas. After the air intake stops, the second elastic member returns to its original position and drives the piston head to close the exhaust hole.

[0020] Preferably, the stiffness coefficient of the second elastic member is greater than the stiffness coefficient of the first elastic member.

[0021] Preferably, the calibration tube comprises:

[0022] An adjusting sleeve is sleeved on the outside of the calibration tube, and the adjusting sleeve is connected to the limiting ring via a connecting rod penetrating the wall of the calibration tube;

[0023] The adjusting assembly is installed on the calibration tube and is connected to the adjusting sleeve. The adjusting assembly is used to drive the adjusting sleeve to move along the axis of the calibration tube to adjust the position of the limiting ring in the tube.

[0024] Preferably, the adjustment component includes:

[0025] A nut, mated with the thread on the outer wall of the calibration tube;

[0026] The connecting plate is fixed to one end of the adjusting sleeve and is in the shape of a circular ring. The connecting plate is sleeved on the calibration tube. The nut is installed on the connecting plate. The adjusting sleeve is driven to move axially by rotating the nut.

[0027] Preferably, the adjustment component includes:

[0028] The electric slide is installed on the calibration tube, the adjustment sleeve is connected to the slider of the electric slide, and the electric slide is used to drive the axial displacement of the adjustment sleeve.

[0029] Preferably, a temperature sensor is provided in the sample inlet tube, and the temperature sensor is electrically connected to the electric slide through a PLC control system, and is used to adjust the position of the limit ring according to the detected sample gas temperature to compensate for the difference in gas molar amount.

[0030] Preferably, the three-way valve is an electric L-shaped three-way ball valve, which is controlled by a solenoid valve to switch the connection state between the sample injection tube and the calibration tube, and between the calibration tube and the air inlet pipe.

[0031] Preferably, the main piston further comprises:

[0032] The connecting ring is threadedly matched with the outer wall of the main piston, and the cleaning head is installed on the outer ring of the connecting ring;

[0033] Sealing ring, installed on the outer ring of the main piston.

[0034] Preferably, the cleaning head adopts an elastic porous silica gel matrix, the surface of which is embedded with activated carbon fiber felt or polar adsorption resin particles.

[0035] The present invention provides a gas sampling calibration mechanism for gas chromatography. Compared with the prior art, it has the following beneficial effects: a main piston is used to directly push the sample gas, and the initial position of the main piston directly abuts the gas outlet of the three-way valve. After calibration is completed, the first elastic member pushes the main piston back to its original position, pressing the sample gas into the chromatographic column without any intermediate links. This avoids sample gas mixing caused by pre-filling the dead volume with the push gas, eliminates ghost peak interference introduced by impurities in the push gas, and improves the accuracy of qualitative and quantitative analysis of target components. When the main piston is reset to push the sample gas, the cleaning head slides closely against the inner wall of the calibration tube to achieve physical scraping. The activated carbon fiber felt or polar adsorption resin particles embedded in the surface respectively capture residual substances by adsorption for non-polar organic matter and polar compounds such as alcohols and carboxylic acids. The cleaning head adopts a threaded quick-release connection, which supports rapid replacement. By reducing push gas interference and efficiently cleaning residues, the impact of impurity accumulation on the chromatographic column and test results is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of the three-dimensional structure proposed by the present invention.

[0037] Figure 2 This is a schematic cross-sectional view of the calibration tube and adjustment sleeve proposed in the present invention.

[0038] Figure 3 This is a schematic structural diagram of the calibration tube, main piston and adjustment sleeve proposed in the present invention.

[0039] Figure 4 This is a cross-sectional schematic diagram of the adjustment sleeve proposed in the present invention.

[0040] Figure 5 This is a cross-sectional schematic diagram of the calibration tube, main piston and adjustment sleeve proposed in the present invention.

[0041] Figure 6 This is a schematic diagram of the main piston structure proposed in the present invention.

[0042] Figure 7 for Figure 6 Schematic cross-section of .

[0043] Figure 8 This is a schematic diagram of the structure of the adjustment component proposed in Example 2.

[0044] The reference numerals in the figures are:

[0045] 100, calibration tube; 101, first elastic member; 102, distance measuring sensor;

[0046] 200, three-way valve; 201, sample injection tube; 202, air inlet pipe; 203, temperature sensor;

[0047] 300, main piston; 301, one-way valve; 302, cavity; 303, piston head; 304, second elastic member; 305, exhaust hole; 306, sealing ring; 307, connecting ring; 308, cleaning head;

[0048] 400, adjusting sleeve; 401, connecting rod; 402, limiting ring; 403, connecting plate; 404, nut; 405, electric slide. DETAILED DESCRIPTION

[0049] The present invention is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention.

[0050] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0051] Example 1: Reference Figure 1-Figure 7 , a gas sampling calibration mechanism for gas chromatography, comprising:

[0052] The calibration tube 100 has an open end, and a first elastic member 101 and a distance sensor 102 are installed on the inner wall of the other end. The distance sensor 102 is a magnetostrictive displacement sensor.

[0053] The three-way valve 200 has a first air outlet connected to the open end of the calibration tube 100, a second air outlet connected to the air inlet pipe 202 and connected to the chromatographic column, and an air inlet connected to the sample injection tube 201. The three-way valve 200 adopts an electric L-shaped three-way ball valve, and the solenoid valve is controlled to realize the switching of the connection status between the sample injection tube 201 and the calibration tube 100, and the calibration tube 100 and the air inlet pipe 202.

[0054] The main piston 300 is arranged in the calibration tube 100 and its initial position abuts the air outlet of the three-way valve 200. One end of the main piston 300 is connected to the first elastic member 101, and the other end is equipped with a cleaning head 308 that contacts the inner wall of the calibration tube 100. The distance sensor 102 is connected to the main piston 300. When the three-way valve 200 is switched to the connection between the sample injection tube 201 and the calibration tube 100, the sample gas pushes the main piston 300 to compress the first elastic member 101, and the distance sensor 102 detects the displacement of the main piston 300; when the three-way valve 200 is switched to the connection between the calibration tube 100 and the air inlet pipe 202, the first elastic member 101 releases the elastic force to push the main piston 300 to reset, and the cleaning head 308 scrapes the tube wall of the calibration tube 100 and pushes the gas into the chromatographic column.

[0055] Three-way valve 200 switches to connect the sample inlet tube 201 to the calibration tube 100. Sample gas enters the calibration tube 100 through the sample inlet tube 201, pushing the main piston 300 away from the three-way valve 200, compressing the first elastic member 101 to store elastic potential energy. Distance sensor 102 monitors the displacement of the main piston 300 in real time. When the displacement reaches a preset value, the calibration tube 100 is filled with the correct volume of sample gas. For example, a 10mm displacement of the main piston 300 corresponds to a 100μL gas volume. A displacement accuracy of ±0.05mm achieves a volume error of less than ±0.5%. If continued gas inflow causes pressure to rise, the one-way valve 301 within the main piston 300 opens, allowing excess gas to enter the piston cavity 302 and be discharged through the exhaust hole 305, ensuring a constant gas volume within the calibration tube 100.

[0056] The three-way valve 200 switches the calibration tube 100 to connect with the inlet pipe 202. The first elastic member 101 releases its force, rapidly resetting the main piston 300 and forcing the sample gas in the calibration tube 100 into the chromatographic column through the inlet pipe 202. During this resetting process, the cleaning head 308 slides against the inner wall of the calibration tube 100, scraping and adsorbing any remaining high-boiling-point components or particles, preventing their accumulation on the tube wall. For example, the single-pass removal rate for polar residues such as acetic acid can exceed 85%.

[0057] The main piston 300 directly pushes the sample gas into the chromatographic column through elastic force without the need for additional push gas, fundamentally eliminating ghost peak interference introduced by push gas impurities.

[0058] The limiting ring 402 is axially movable in the calibration tube 100 and is used to limit the stroke of the main piston 300. The calibration tube 100 includes: an adjusting sleeve 400, which is sleeved on the outside of the calibration tube 100, and the adjusting sleeve 400 is connected to the limiting ring 402 through a connecting rod 401 that penetrates the wall of the calibration tube 100; an adjusting component, which is installed on the calibration tube 100 and is connected to the adjusting sleeve 400, and the adjusting component is used to drive the adjusting sleeve 400 to move along the axis of the calibration tube 100 to adjust the position of the limiting ring 402 in the tube; the adjusting component includes: a nut 404, which is threadedly engaged with the outer wall of the calibration tube 100; a connecting rod 401 that penetrates the wall of the calibration tube 100; and a connecting rod 402 that is connected to the connecting rod 401. The connecting plate 403 is fixed to one end of the adjusting sleeve 400 and is in a circular ring shape. The connecting plate 403 is sleeved on the calibration tube 100, and the nut 404 is installed on the connecting plate 403. By rotating the nut 404, the adjusting sleeve 400 is driven to axially move, and the position of the limit ring 402 on the calibration tube 100 is adjusted. The purpose of adjusting the limit ring 402 is to adjust the moving range of the main piston 300, thereby adjusting the intake volume. When more air intake is required, the limit ring 402 is moved away from the main piston 300, the moving range of the main piston 300 is expanded, and the intake volume increases. Conversely, the moving range of the main piston 300 is reduced and the intake volume is reduced.

[0059] During manual adjustment, the user rotates nut 404 with the included hexagonal wrench, driving the axial movement of connecting plate 403 and adjustment sleeve 400. Each rotation moves stop ring 402 by 1 mm, corresponding to a change in calibration volume of approximately 50 μL (based on a 4 mm inner diameter of calibration tube 100). After adjustment, the threads of nut 404 and the outer wall of calibration tube 100 self-lock to prevent positional shifting caused by vibration.

[0060] Adjusting the position of the limit ring 402 changes the maximum stroke of the main piston 300, thereby adjusting the calibration volume. For example, moving the limit ring 402 5mm away from the three-way valve 200 can increase the calibration volume from 100μL to 150μL, adapting to the testing requirements of samples of varying concentrations. The target displacement value of the distance sensor 102 is linked in real time to the position of the limit ring 402. That is, when the position of the limit ring 402 changes, the PLC control system simultaneously updates the preset displacement value. The position of the limit ring 402 determines the maximum stroke and target volume of the main piston 300. The target displacement feedback value always equals the stroke value corresponding to the current position of the limit ring 402.

[0061] When the adjustment assembly changes the position of the limit ring 402, the PLC control system updates the target displacement by the following steps:

[0062] After the limit ring 402 moves to the new position, it triggers the origin sensor (Hall switch) installed at the end of the calibration tube 100 to determine the mechanical zero point;

[0063] According to the distance between the current position of the limit ring 402 and the mechanical zero point, the target displacement value of the main piston 300 is calculated and synchronized to the feedback reference of the distance sensor 102.

[0064] The main piston 300 includes: a cavity 302, which is opened in the main piston 300, and the end surface of the main piston 300 facing the open end of the calibration tube 100 is provided with a through hole connected to the cavity 302; a one-way valve 301, which is installed in the through hole; an exhaust hole 305, which is opened in the inner wall of the cavity 302 and passes through the top of the main piston 300; a piston head 303, which is installed in the cavity 302 and is connected to the inner wall of the cavity 302 through a second elastic member 304; when the main piston 300 moves to the limit ring 402, it continues to The incoming gas enters the cavity 302 through the one-way valve 301 and pushes the piston head 303 to compress the second elastic member 304, so that the exhaust hole 305 is opened to discharge excess gas. After the intake stops, the second elastic member 304 returns to its original position and drives the piston head 303 to close the exhaust hole 305. The rigidity coefficient of the second elastic member 304 is greater than the rigidity coefficient of the first elastic member 101. The first elastic member 101 and the second elastic member 304 both adopt constant elastic modulus alloy springs, and can also adopt beryllium bronze springs. The one-way valve 301 is a spring-loaded one-way valve 301.

[0065] On the one hand, when the sample gas enters the calibration tube 100 and pushes the main piston 300, the piston head 303 remains stationary due to the greater rigidity of the second elastic member 304, and the exhaust hole 305 is sealed by the piston head 303. Under the action of the gas pressure, the main piston 300 compresses the first elastic member 101 until it contacts the limit ring 402, at which point normal volume calibration is completed;

[0066] If the injection pressure continues to rise, when the pressure exceeds the opening threshold of the one-way valve 301, excess gas enters the cavity 302 through the through hole, pushing the piston head 303 upward to overcome the elastic force of the second elastic member 304. When the piston head 303 rises to expose the exhaust hole 305, the excess gas is discharged from the calibration tube 100 through the exhaust hole 305, avoiding volume errors caused by excessive pressure.

[0067] After the injection is completed, the gas pressure drops, and the second elastic member 304 pushes the piston head 303 to return to its original position, resealing the exhaust hole 305. At this time, the gas volume retained in the calibration tube 100 is the precisely controlled target volume.

[0068] By opening and closing vent 305, piston head 303 ensures that the volume of gas in calibration tube 100 does not exceed the maximum value set by limit ring 402. For example, when limit ring 402 is set to 100 μL, even if the injection system mistakenly injects 120 μL of gas, the excess 20 μL will be discharged through vent 305, ensuring that the volume of gas ultimately entering the chromatographic column remains constant.

[0069] On the other hand, when the distance measuring sensor 102 collects the position signal of the main piston 300 in real time and compares it with the target displacement value preset by the PLC, when it detects that the displacement of the main piston 300 is less than the preset value, the PLC determines that the air intake is insufficient, triggers the air supply solenoid valve to open, and continues to supply gas through the sampling tube 201. If the air supply is excessive, the excess gas enters the cavity 302 through the through hole and is discharged from the calibration tube 100 through the exhaust hole 305.

[0070] On the other hand, if the high-temperature gas cools down while flowing in the pipeline, its volume will also shrink. The main piston 300 is initially pushed to the position of the limit ring 402 by the high-temperature gas. However, the volume of the gas shrinks after cooling down, and the main piston 300 moves in the opposite direction under the action of the first elastic member 101, resulting in a decrease in the actual displacement. The PLC determines that the volume is insufficient due to the cooling and shrinkage of the gas, and triggers the gas replenishment program. However, the specific replenishment amount cannot be determined when replenishing gas again. Through the exhaust hole 305 and the movable piston head 303, the pipeline pressure exceeds the target value during the gas replenishment process, and the excess gas enters the cavity 302 through the one-way valve 301 on the end face of the main piston 300, pushing the piston head 303 to compress the second elastic member 304 and move it upward. After the piston head 303 moves upward, the exhaust hole 305 is exposed, and the excess gas is discharged; when the pressure drops, the second elastic member 304 is reset, and the piston head 303 seals the exhaust hole 305, ensuring that the final volume is strictly equal to the set value of the limit ring 402.

[0071] Temperature pre-compensation is a primary control, which prioritizes adjusting the position of the limit ring 402 to match the temperature; displacement feedback is a secondary control, which corrects the remaining error only after the position of the limit ring 402 is fixed, and temporarily locks the feedback air supply function when the electric slide 405 adjusts the limit ring 402; after the adjustment is completed, the displacement feedback is enabled for fine-tuning.

[0072] The main piston 300 also includes: a connecting ring 307, which is threadedly engaged with the outer wall of the main piston 300, and a cleaning head 308 is installed on the outer ring of the connecting ring 307; a sealing ring 306, which is installed on the outer ring of the main piston 300, and the sealing ring 306 is made of perfluoroether rubber. The sealing ring 306 is fixed to the outer ring of the main piston 300 through an annular groove; the cleaning head 308 adopts an elastic porous silica gel matrix, and its surface is embedded with activated carbon fiber felt or polar adsorption resin particles to form a composite layer with dual functions of physical wiping and chemical adsorption.

[0073] The above-mentioned silica gel matrix provides elastic deformation ability, ensuring a close fit with the inner wall of the calibration tube 100, effectively removing granular or film-like residues; the activated carbon fiber felt has an adsorption capacity of 50 to 100 mg / g for non-polar organic matter (such as alkanes and siloxanes), and the polar resin particles have an adsorption capacity of 80 to 150 mg / g for alcohols and carboxylic acids, meeting the collection needs of different residues; the surface of the cleaning head 308 is coated with a polytetrafluoroethylene nano-coating to reduce surface energy and reduce the adhesion of high-boiling point components (such as C15+), while improving temperature resistance to adapt to temperature fluctuations in the vehicle environment.

[0074] The cleaning head 308 is connected to the main piston 300 through a connecting ring 307 using a threaded quick-release connection, which ensures sealing while supporting quick replacement. A color-changing silicone strip is embedded in the edge of the cleaning head 308. When the adsorption of organic matter reaches saturation, the silicone strip changes from blue to pink, prompting the user to replace it.

[0075] Example 2: Reference Figure 8 The difference between this embodiment and the first embodiment is that the adjustment component includes an electric slide 405, which is installed on the calibration tube 100, and the adjustment sleeve 400 is connected to the slider of the electric slide 405. The electric slide 405 is used to drive the axial displacement of the adjustment sleeve 400. A temperature sensor 203 is provided in the injection tube 201. The temperature sensor 203 is electrically connected to the electric slide 405 through a PLC control system, and is used to adjust the position of the limit ring 402 according to the detected sample gas temperature to compensate for the difference in gas molar amount.

[0076] The temperature sensor 203 adopts a PT100 platinum resistance temperature sensor 203, which is inserted into the center of the sample injection tube 201 and is covered with a 316L stainless steel protective sleeve to prevent corrosion from the sample gas. The PLC control system adopts Siemens S7-1200 series PLC (CPU1214C), with a processing cycle of <1ms and supports PID control algorithm;

[0077] Before injection: the temperature sensor 203 continuously samples 3 times and takes the average value, the PLC calculates the compensation position and drives the electric slide 405 to adjust the limit ring 402;

[0078] During the injection process: real-time monitoring of temperature changes, if the fluctuation exceeds ±2°C, dynamic compensation is triggered;

[0079] After calibration is completed: the slide returns to its initial position and the positioning error is corrected by the origin sensor. The temperature compensation formula built into the PLC control system is:

[0080]

[0081] in:

[0082] L0 is the position of the limit ring 402 at standard temperature (25°C), T ref =25℃, T sample is the measured sample temperature (℃);

[0083] 273.15 is the offset in the Celsius to Kelvin conversion, used to convert relative temperatures to absolute temperatures.

[0084] This formula is derived based on the ideal gas law. When the gas is non-ideal, the user can enter the compression factor Z through the human-machine interface to make corrections.

[0085] Since the separation and detection of gas chromatography is based on the distribution coefficient of each component in the sample in the stationary phase and the mobile phase, the ultimate quantitative basis is the amount of substance, not the volume of the gas; the same volume of gas, if the temperature is different, the amount of substance will be significantly different, and simply calibrating the volume will lead to deviation in the amount of substance. In this embodiment, when calibrating high-temperature gas, the high-temperature gas enters the calibration mechanism. Due to the high gas temperature, the thermal motion of the gas molecules is intensified, and the gas of the same amount of substance will occupy a larger volume. At this time, if the fixed volume at room temperature is still used for sampling, the number of molecules of high-temperature gas that actually enter will be less than that of room-temperature gas, resulting in deviation in the detection results. The purpose of introducing the temperature sensor 203 is to:

[0086] The temperature sensor 203 in the injection tube 201 detects the temperature of the sample gas in real time. When high-temperature gas is detected, its temperature is significantly higher than the standard temperature. At this time, the number of molecules in the same volume of gas is smaller.

[0087] The electric slide 405 drives the adjustment sleeve 400 to move axially along the calibration tube 100 based on the signal from the temperature sensor 203, driving the internal limit ring 402 to move away from the main piston 300. The limit ring 402 is the end point of the main piston 300's movement. Its position determines the maximum stroke of the main piston 300 and, in turn, the effective volume of the calibration tube 100.

[0088] When the stop ring 402 moves away from the main piston 300, the main piston 300's range of movement expands, and the volume of gas that the calibration tube 100 can accommodate increases. For example, at room temperature, the stop ring 402 allows the main piston 300 to move 20 mm (corresponding to a volume of 100 μL). At high temperatures, the stop ring 402 moves outward to 22 mm, increasing the calibration volume to 110 μL. This allows more high-temperature gas to enter, compensating for the decrease in the number of molecules caused by the temperature increase.

[0089] The electric slide 405 is driven by a high-precision ball screw (with an accuracy of ±0.01mm) to ensure that the position adjustment of the limit ring 402 accurately matches the temperature change. The PLC control system has a built-in compensation algorithm that automatically calculates the target position of the limit ring 402 according to the ideal gas law, so that the number of gas molecules entering at different temperatures remains consistent.

[0090] During use, the motorized slide 405 drives the adjustment sleeve 400 to the mechanical origin. At this point, the limit ring 402 is in its initial position within the calibration tube 100, closest to the three-way valve 200, corresponding to the minimum calibration volume (e.g., 50 μL). Simultaneously, the solenoid valve controls the three-way valve 200, switching the calibration tube 100 to a state of communication with the intake pipe 202. The main piston 300, under the elastic force of the first elastic member 101, returns to its original position, and the cleaning head 308 rests against the open end of the calibration tube 100, ready for sample injection.

[0091] The operator inputs the standard temperature and target calibration volume through the human-machine interface. The PLC control system initializes the relevant parameters and prepares for subsequent calculations. Based on the sample concentration requirements, the operator uses a hexagonal wrench to rotate nut 404, which engages the threads on the outer wall of calibration tube 100, driving the axial movement of connecting plate 403 and adjustment sleeve 400. With each rotation, limit ring 402 moves 1mm, corresponding to a change in calibration volume of approximately 50μL. After adjustment, nut 404 and the threads on the outer wall of calibration tube 100 achieve self-locking, preventing vibration during operation from causing the limit ring 402 to shift in position. Simultaneously, the PLC control system determines the mechanical zero point based on the new position of limit ring 402 using the origin sensor (Hall switch) at the end of calibration tube 100. It then calculates and updates the target displacement value of main piston 300, synchronizing it with the feedback reference of distance sensor 102.

[0092] The PT100 platinum resistance temperature sensor 203 in the injection tube 201 collects the sample gas temperature at a frequency of 10Hz. After three consecutive samplings, the average value is taken to obtain accurate sample gas temperature data. The PLC control system calculates the target displacement of the limit ring 402 according to the ideal gas compensation formula. For example, if L0 is 20mm (corresponding to a volume of 100μL at standard temperature), the calculation results are L≈21.69mm, which means that the limit ring 402 needs to be moved 1.69mm away from the main piston 300 to increase the calibration volume from 100μL to 108.4μL. Subsequently, the electric slide 405 drives the adjustment sleeve 400 axially at a speed of 10mm / s, and the limit ring 402 is positioned to the calculated position by a high-precision ball screw. The origin sensor is triggered to confirm the position and then the limit ring 402 is locked. During this process, the feedback air supply function is temporarily locked to avoid conflict between the adjustment and air supply actions.

[0093] The solenoid valve controls the three-way valve 200 to switch to a state where the sample injection tube 201 and the calibration tube 100 are connected. The sample gas enters the calibration tube 100 through the sample injection tube 201, pushing the main piston 300 to move away from the three-way valve 200, compressing the first elastic member 101 to store elastic potential energy. The magnetostrictive displacement sensor provides real-time feedback on the position of the main piston 300 at 5 ms intervals. When it is detected that the displacement of the main piston 300 reaches a preset value (the target displacement after manual adjustment in Example 1; the displacement after temperature compensation calculation in Example 2), the PLC determines that the calibration tube 100 has been filled with an accurate volume of sample gas.

[0094] If continued air intake causes the pressure to rise (e.g., exceeding 0.15 MPa), the spring-loaded one-way valve 301 (opening pressure 0.03 MPa) within the main piston 300 opens, allowing excess gas to enter the piston cavity 302, pushing the piston head 303 upward, overcoming the elastic force of the second elastic member 304 (with a greater elastic modulus than the first elastic member 101, e.g., 10 N / m). When the piston head 303 moves upward by 2 mm, revealing the exhaust hole 305 (0.8 mm diameter), the excess gas is discharged from the calibration tube 100 at a flow rate of 20 μL / s until the pressure returns to 0.1 MPa, ensuring a constant gas volume within the calibration tube 100.

[0095] The distance sensor 102 collects the real-time position signal of the main piston 300 and compares it with the target displacement value preset by the PLC. If the displacement of the main piston 300 is less than the preset value, the PLC determines that the air intake is insufficient. Furthermore, if the high-temperature gas cools while flowing through the pipeline, its volume shrinks, causing the main piston 300 to move in the opposite direction under the action of the first elastic member 101, reducing the actual displacement and triggering the air replenishment process.

[0096] The PLC triggers the opening of the gas replenishment solenoid valve, which continues to replenish gas through the sample inlet tube 201. Initially, gas replenishment is performed at a high rate of 50 mL / min. When the displacement of the main piston 300 approaches the target value (e.g., a difference of 0.5 mm), the flow rate is switched to a low rate of 10 mL / min until the target displacement is reached. If excessive gas is replenished, the excess gas enters the cavity 302 through the through-hole on the end face of the main piston 300 and is discharged from the calibration tube 100 through the exhaust port 305, ensuring that the final volume equals the set value of the limit ring 402.

[0097] The three-way valve 200 switches to a state where the calibration tube 100 is connected to the air inlet pipe 202 , and the first elastic member 101 releases its elastic force, pushing the main piston 300 to quickly reset, pressing the sample gas in the calibration tube 100 into the chromatographic column through the air inlet pipe 202 for detection.

[0098] During the return of the main piston 300, the cleaning head 308 slides against the inner wall of the calibration tube 100, scraping and adsorbing any remaining high-boiling-point components or particles. The activated carbon fiber felt has an adsorption capacity of 50-100 mg / g for non-polar organic matter, and the polar resin particles have an adsorption capacity of 80-150 mg / g for alcohols and carboxylic acids. The single-pass removal rate for polar residues such as acetic acid can exceed 85%. Furthermore, the surface coating of the cleaning head 308 reduces surface energy, preventing the adhesion of high-boiling-point components and accommodating temperature fluctuations in complex environments such as those found on vehicles.

[0099] In summary, compared with the existing technology, it has the following beneficial effects:

[0100] The main piston 300 is used to directly push the sample gas. The initial position of the main piston 300 directly abuts the outlet of the three-way valve 200. After the calibration is completed, the first elastic member 101 pushes the main piston 300 to reset, and the sample gas is pressed into the chromatographic column without any intermediate links, avoiding the mixing of the sample gas caused by the dead volume pre-filled by the push gas, eliminating the ghost peak interference introduced by the impurities in the push gas, and improving the accuracy of the qualitative and quantitative analysis of the target components.

[0101] When the main piston 300 resets to push the sample gas, the cleaning head 308 slides close to the inner wall of the calibration tube 100 to achieve physical scraping. The activated carbon fiber felt or polar adsorption resin particles embedded on the surface respectively target non-polar organic matter and polar compounds such as alcohols and carboxylic acids, and use adsorption to capture residual substances. The cleaning head 308 adopts a threaded quick-release connection to support quick replacement. By reducing the interference of the pushing gas and efficiently cleaning the residue, the impact of impurity accumulation on the chromatographic column and test results is reduced.

[0102] The displacement of the main piston 300 is monitored in real time by the distance sensor 102, and the stroke of the main piston 300 is adjusted in combination with the limit ring 402 to achieve accurate calibration of the injection volume. During manual adjustment, the nut 404 is rotated to finely change the position of the limit ring 402, and each rotation corresponds to a stable change in the calibration volume; during electric adjustment, according to the detection data of the temperature sensor 203, the PLC system calculates and automatically adjusts the limit ring 402 based on the ideal gas compensation formula to compensate for the molar difference of the high-temperature gas caused by the temperature. The piston head 303 and the exhaust hole 305 in the main piston 300 are designed to automatically discharge excess gas when excessive air intake or excessive air replenishment occurs, ensuring that the gas volume in the calibration tube 100 is strictly equal to the set value of the limit ring 402.

[0103] When faced with the situation where high-temperature gas cools down and shrinks in the pipeline, resulting in insufficient volume, the distance measuring sensor 102 compares the displacement of the main piston 300 with the preset value in real time. Once insufficient displacement is detected, the air replenishment program is triggered. Combined with the exhaust function of the piston head 303, precise control of the air replenishment amount is achieved. The temperature pre-compensation and displacement feedback two-level control mechanism enables the system to pre-adjust the limit ring 402 according to the temperature before injection, and to correct dynamic errors during the injection process, adapting to complex working conditions such as different temperatures and pressures, and ensuring stable operation of the injection system.

[0104] Thus, although the invention has been described herein with reference to specific embodiments thereof, freedom of modification, various changes and substitutions are contemplated within the foregoing disclosure, and it should be understood that in some cases, some features of the invention will be employed without the corresponding use of other features without departing from the scope and spirit of the claimed invention. Thus, many modifications may be made to adapt a particular environment or material to the true scope and spirit of the invention. The invention is not intended to be limited to the specific terminology used in the claims below and / or to the specific embodiments disclosed as the best mode contemplated for carrying out the invention, but the invention is intended to include any and all embodiments and equivalents falling within the scope of the appended claims. Thus, the scope of the invention will be determined solely by the appended claims.

Claims

1. A gas sampling calibration mechanism for gas chromatography, characterized in that: include: A calibration tube (100) with an opening at one end and a first elastic member (101) and a distance sensor (102) mounted on the inner wall of the other end; A three-way valve (200), wherein a first air outlet is connected to the open end of the calibration tube (100), a second air outlet is connected to an air inlet (202) and communicates with the chromatographic column, and an air inlet is connected to a sample injection tube (201); A main piston (300) is disposed in the calibration tube (100) and abuts against the air outlet of the three-way valve (200) at its initial position. One end of the main piston (300) is connected to the first elastic member (101), and the other end is provided with a cleaning head (308) in contact with the inner wall of the calibration tube (100); A limiting ring (402) is axially movably disposed in the calibration tube (100) and is used to limit the stroke of the main piston (300); When the three-way valve (200) is switched to connect the sample injection tube (201) to the calibration tube (100), the sample gas pushes the main piston (300) to compress the first elastic member (101), and the distance sensor (102) detects the displacement of the main piston (300); When the three-way valve (200) is switched to connect the calibration tube (100) and the air inlet pipe (202), the first elastic member (101) releases elastic force to push the main piston (300) to reset, and the cleaning head (308) scrapes the wall of the calibration tube (100) and pushes the gas into the chromatographic column.

2. The gas sampling calibration mechanism for gas chromatography according to claim 1, characterized in that: The main piston (300) comprises: A cavity (302) is provided in the main piston (300), and a through hole communicating with the cavity (302) is provided on the end surface of the main piston (300) facing the open end of the calibration tube (100); a one-way valve (301), installed in the through hole; An exhaust hole (305) is formed on the inner wall of the cavity (302), and the exhaust hole (305) passes through the top of the main piston (300); A piston head (303) is installed in the cavity (302), and the piston head (303) is connected to the inner wall of the cavity (302) through a second elastic member (304); When the main piston (300) moves to the limiting ring (402), the continuously entering gas enters the cavity (302) through the one-way valve (301) and pushes the piston head (303) to compress the second elastic member (304), so that the exhaust hole (305) is opened to discharge excess gas. After the intake stops, the second elastic member (304) returns to its original position and drives the piston head (303) to close the exhaust hole (305).

3. The gas sampling calibration mechanism for gas chromatography according to claim 2, characterized in that: The rigidity coefficient of the second elastic member (304) is greater than the rigidity coefficient of the first elastic member (101).

4. The gas sampling calibration mechanism for gas chromatography according to claim 1, characterized in that: The calibration tube (100) comprises: An adjusting sleeve (400) is sleeved on the outside of the calibration tube (100), and the adjusting sleeve (400) is connected to a limiting ring (402) via a connecting rod (401) penetrating the wall of the calibration tube (100); The adjusting assembly is mounted on the calibration tube (100) and connected to the adjusting sleeve (400). The adjusting assembly is used to drive the adjusting sleeve (400) to move along the axis of the calibration tube (100) to adjust the position of the limiting ring (402) in the tube.

5. The gas sampling calibration mechanism for gas chromatography according to claim 4, characterized in that: The adjustment component includes: A nut (404) is threadably coupled to an outer wall of the calibration tube (100); The connecting plate (403) is fixed to one end of the adjusting sleeve (400) and is in a circular ring shape. The connecting plate (403) is sleeved on the calibration tube (100). The nut (404) is installed on the connecting plate (403). The adjusting sleeve (400) is driven to move axially by rotating the nut (404).

6. The gas sampling calibration mechanism for gas chromatography according to claim 4, characterized in that: The adjustment component includes: The electric slide (405) is installed on the calibration tube (100), the adjustment sleeve (400) is connected to the slider of the electric slide (405), and the electric slide (405) is used to drive the adjustment sleeve (400) to axially displace.

7. The gas sampling calibration mechanism for gas chromatography according to claim 6, characterized in that: A temperature sensor (203) is provided in the sample injection tube (201), and the temperature sensor (203) is electrically connected to the electric slide (405) through a PLC control system, and is used to adjust the position of the limit ring (402) according to the detected sample gas temperature to compensate for the difference in gas molar amount.

8. The gas sampling calibration mechanism for gas chromatography according to claim 1, characterized in that: The three-way valve (200) is an electric L-shaped three-way ball valve, which is controlled by a solenoid valve to switch the communication state between the sample injection tube (201) and the calibration tube (100), and between the calibration tube (100) and the air inlet tube (202).

9. The gas sampling calibration mechanism for gas chromatography according to claim 1, characterized in that: The main piston (300) further comprises: A connecting ring (307) is threadably coupled to the outer wall of the main piston (300), and a cleaning head (308) is mounted on the outer ring of the connecting ring (307); A sealing ring (306) is mounted on the outer ring of the main piston (300).

10. The gas sampling calibration mechanism for gas chromatography according to claim 1, characterized in that: The cleaning head (308) adopts an elastic porous silica gel matrix, and the surface of the matrix is ​​embedded with activated carbon fiber felt or polar adsorption resin particles.

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