A liquid chromatography automatic sampler control method and system based on pressure feedback

Abstract

The application belongs to the technical field of analytical chemistry instruments, and particularly relates to a liquid chromatography automatic sampler control method and system based on pressure feedback, wherein the method comprises the following steps: acquiring a real-time pressure value in a high-pressure flow path of a liquid chromatography system; determining a target sealing force required for maintaining sealing under the current pressure; converting the target sealing force into a target displacement amount required to be executed by a Z-axis driving mechanism according to an elastic coefficient of an elastic element arranged in series between the Z-axis driving mechanism and a sampling needle; and when a critical position where the sampling needle contacts a sealing assembly is detected, controlling the Z-axis driving mechanism to continue moving from the critical position by the target displacement amount, so that the elastic element is deformed and the target sealing force is applied to the sampling needle. The application realizes dynamic sealing control according to needs, converts a complex force control problem into an accurate displacement control problem, significantly prolongs the service life of consumables such as sealing gaskets, and improves sealing reliability and sampling repeatability.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry instrumentation technology, and in particular to a method and system for controlling an automated liquid chromatograph based on pressure feedback. Background Technology

[0002] High-performance liquid chromatography (HPLC) is an essential tool in analytical chemistry for separating and detecting complex mixtures. The autosampler, as its core component, is primarily responsible for accurately quantifying samples and introducing them into the high-pressure mobile phase system. During injection, the injection needle is inserted into the high-pressure injection port and tightly pressed against the internal sealing gasket (usually made of wear-resistant elastic materials such as PEEK or Vespel), forming a sealed interface capable of withstanding the system's high pressure (typically 10-100 MPa or even higher). The reliability of this seal directly affects the accuracy of the analytical results and the safety of the system.

[0003] Currently, the closest existing technology in the industry includes the autosampler structure described in the applicant team's previously granted patent (CN106770848B). This technology achieves adaptive alignment of the injection port in the horizontal plane (XY axis) by introducing a floating sealing ring seat and hose connection structure, solving the problems of injection needle positioning accuracy and alignment accuracy with the sealing gasket. However, existing autosampler technologies still employ mechanical hard sealing or constant parameter control strategies for sealing pressure control (Z-axis force control). That is, a constant number of pressing steps or torque value is usually set according to the highest operating pressure that the device can reach (e.g., 100MPa). This results in the Z-axis drive mechanism driving the injection needle to compress the sealing gasket with the force of the highest pressure, regardless of whether the system pressure of the current actual analysis task is low or high. This constant control method leads to the sealing gasket being subjected to mechanical pressure far exceeding the actual requirements under most conventional low-pressure conditions, causing excessive compression and accelerated plastic deformation of the sealing material, thereby greatly shortening the service life of consumables and increasing the risk of leakage under high-pressure conditions later. Summary of the Invention

[0004] This invention proposes a pressure feedback-based control method and system for an automatic liquid chromatograph, aiming to solve the technical problems of short lifespan and poor reliability of the sealing gasket caused by constant overload force applied to the liquid chromatograph in the prior art.

[0005] In a first aspect, the present invention provides a pressure feedback-based automatic liquid chromatography sampler control method, comprising: The real-time pressure value in the high-pressure flow path of a liquid chromatograph is obtained. The liquid chromatograph includes an injection needle and a Z-axis drive mechanism for driving the injection needle to move up and down in the vertical direction. Based on the real-time pressure value, determine the target sealing force required to maintain the seal under the current pressure; Based on the elastic coefficient of the elastic element connected in series between the Z-axis drive mechanism and the injection needle, the target sealing force is converted into the target displacement amount that the Z-axis drive mechanism needs to perform; The Z-axis drive mechanism is controlled to drive the injection needle to descend, and when a critical position is detected where the injection needle contacts the sealing assembly, the Z-axis drive mechanism is controlled to drive the injection needle to continue moving the target displacement from the critical position, so that the elastic element deforms and applies the target sealing force to the injection needle.

[0006] The technical advantage of the pressure feedback-based automatic liquid chromatography sampler control method disclosed in this invention is that by acquiring the system pressure value in real time and calculating the target sealing force based on the pressure value, and then converting the target sealing force into a precise displacement for execution, this method completely abandons the crude mode of "applying a constant overload force according to the system's highest rated pressure" in traditional technology. When the system pressure is low, only a smaller sealing force matching it is applied, avoiding unnecessary overload pressure on the sealing gasket.

[0007] Furthermore, determining the target sealing force required to maintain the seal at the current pressure based on the real-time pressure value specifically includes: Based on the preset function model Determine the target sealing force, wherein The target sealing force, The real-time pressure value, The minimum critical force function required to maintain a seal, This is a preset safety margin factor greater than 1.

[0008] Furthermore, the method also includes: While the injection needle maintains the applied target sealing force, the six-way valve is controlled to switch to the analytical flow path state.

[0009] Secondly, the present invention provides a pressure feedback-based automatic liquid chromatography sampler control system, the system being used to implement the method, the system comprising: The pressure monitoring unit is used to acquire the pressure value in the high-pressure flow path of the liquid chromatography system in real time; the zero-point detection unit is used to detect the critical position of the injection needle in contact with the sealing assembly. The control unit is electrically connected to both the pressure monitoring unit and the zero-point detection unit. The control unit is configured as follows: The target sealing force is determined based on the pressure value obtained by the pressure monitoring unit. The target displacement is determined based on the target sealing force and the elastic coefficient of the elastic element connected in series between the Z-axis drive mechanism and the injection needle. In response to the critical position detected by the zero-point detection unit, the Z-axis drive mechanism is controlled to drive the injection needle to continue moving the target displacement from the critical position, so that the elastic element deforms and applies the target sealing force to the injection needle.

[0010] Furthermore, the control unit is also configured to operate according to a preset function model. Determine the target sealing force, wherein The target sealing force, The real-time pressure value, The minimum critical force function required to maintain a seal, This is a preset safety margin factor greater than 1.

[0011] Furthermore, the control unit is also configured to control the six-way valve to switch to the analysis flow path state after the Z-axis drive mechanism applies the target sealing force.

[0012] Thirdly, the present invention also provides an automated liquid chromatograph sampler, including the system described above.

[0013] Fourthly, a liquid chromatograph includes the aforementioned liquid chromatograph autosampler.

[0014] Fifthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of a pressure feedback-based automatic liquid chromatography sampler control method proposed in an embodiment of the present invention. Figure 2 This is a block diagram illustrating the principle of a pressure feedback-based automatic liquid chromatography sampler control system proposed in an embodiment of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1

[0018] like Figure 1 and Figure 2As shown, this embodiment provides an automated liquid chromatography sampler based on pressure feedback adaptive needle insertion force control. The sampler mainly includes an injection needle and drive assembly, an injection port and sealing assembly, a flow path switching and pressure monitoring unit, a dynamic force application and detection assembly, and an adaptive control system.

[0019] (1) Description of components and structure.

[0020] The injection needle and drive assembly include the injection needle body and a drive mechanism that moves the injection needle body up and down along the Z-axis (vertical direction). In this embodiment, the Z-axis drive mechanism uses a stepper motor in conjunction with a precision lead screw transmission mechanism to achieve high-precision displacement control.

[0021] Inlet and sealing assembly: Located below the injection needle body, it mainly includes the injection platform, sealing ring seat, and the core consumable material mounted thereon—the sealing gasket (i.e., the sealing ring). In a preferred embodiment, to achieve better synergy with the present invention, the inlet assembly can adopt the floating sealing ring seat design from the applicant's authorized patent (CN106770848B). This design allows the sealing gasket to make slight adaptive centering movements in the horizontal plane (XY axis), thereby compensating for horizontal eccentricity during injection needle insertion and achieving horizontal correction. This provides a stable horizontal centering basis for the precise force control of the present invention in the Z-axis direction.

[0022] Flow path switching and pressure monitoring unit: This includes a six-way valve unit and a pressure sensor installed in the high-pressure flow path of the chromatography system (e.g., between the infusion pump and the injection port). This pressure sensor is used to read the actual operating pressure P of the current system flow path in real time and transmit this signal to the control system.

[0023] Dynamic force application and detection component (core mechanical innovation of this invention): An elastic force application element is connected in series between the Z-axis drive mechanism and the injection needle body. In this embodiment, the elastic force application element is preferably a helical spring with a known linear elastic coefficient k. Simultaneously, a position detection sensor (zero-point detection unit), such as a photoelectric switch or a Hall sensor, is configured beside the injection needle drive shaft to accurately capture the critical position where the injection needle tip just contacts the sealing gasket surface and the elastic force application element is about to compress. When this critical position is detected, the sensor outputs a trigger signal.

[0024] The adaptive control system includes a microprocessor (MCU / CPU), memory, and corresponding drive circuitry. The microprocessor is electrically connected to the aforementioned Z-axis drive mechanism (stepper motor), pressure sensor, and zero-point detection unit. The memory stores a computer program containing a "pressure-force-displacement" conversion algorithm.

[0025] (2) Explanation of action relationships and principles.

[0026] The core control principle of this invention lies in abandoning the traditional approach of "applying a fixed needle force according to the system's highest designed rated pressure". During the sample injection process, the control system does not simply issue a fixed downward pressure command, but executes a closed-loop adaptive logic.

[0027] When the injection needle completes sample aspiration and is ready to be inserted into the injection port, the control system first reads the actual pressure P of the current chromatographic system flow path via the pressure sensor. Then, the control system calls upon the built-in engineering mathematical model (target sealing force function model) to calculate the target needle force required to seal the current pressure P. This model can usually be represented as ,in The minimum critical force function for maintaining a seal can be obtained through theoretical mechanical analysis or fitting experimental data. A preset safety margin factor greater than 1 (e.g., 1.2) is used to ensure that there is absolutely no leakage even when the system pressure fluctuates slightly.

[0028] Gain target power Then, the control system converts the force value into a displacement value using Hooke's Law, based on the known linear elastic coefficient k of the elastic force-applying component. That is, the target displacement that the drive mechanism needs to continue pressing downwards after contacting the sealing gasket. satisfy: .

[0029] During the execution phase, the Z-axis drive mechanism lowers the injection needle at a constant speed. When the needle tip just touches the injection port sealing gasket, before the elastic force-applying component is compressed, the zero-point detection unit is triggered, sending a signal to the control system. The control system records the coordinates at this instant as the "zero-point position." Subsequently, the control system uses this zero point as the starting point to precisely control the drive mechanism to continue moving downwards. Distance. At this moment, the elastic force-applying component is compressed. According to Hooke's Law, it will apply a force of size to the injection needle. The axial force. Under the action of this force, the injection needle fits tightly against the sealing gasket, forming a sealing interface.

[0030] Finally, with the injection needle under this pressure, the control system switches the six-way valve to the inject state, allowing the sample to enter the chromatographic column along with the mobile phase for analysis. Throughout the process, the applied sealing force is precisely matched to the actual system pressure, achieving "force application on demand."

[0031] Through the closed-loop workflow of dynamic calculation and displacement control described above, this embodiment effectively solves various problems caused by "constant overload dead force" in existing technologies. For example, existing technologies typically set the downpressure based on a maximum pressure of 100 MPa, which may correspond to a force of 100 N. However, in this embodiment, when the system pressure is only 20 MPa, the calculated downpressure may only be 20 N, significantly reducing the ineffective excess pressure by 80%. This keeps the sealing gasket within a safe elastic deformation range for a long time, avoiding plastic deformation and fatigue. Preliminary tests show that the sealing ring life using the adaptive control of this embodiment is more than 2 to 3 times that of the traditional fixed overload structure. At the same time, because the sealing gasket performance remains good, the system can still maintain excellent sealing performance after long-term use, ensuring high reproducibility of chromatographic analysis.

[0032] Example 2

[0033] This embodiment, based on Embodiment 1 above, provides more detailed step specifications for the control method. For example... Figure 1 As shown, a pressure feedback-based automatic liquid chromatography sampler control method includes the following steps: S1: Real-time pressure acquisition: When the injection needle completes sample aspiration and moves directly above the injection port in preparation for insertion, the control system reads the actual system pressure value P currently fed back by the pressure sensor in the flow path. For example, in an analytical task, the current actual operating pressure is 20 MPa.

[0034] S2: Target Sealing Force Conversion: The control system calls the built-in engineering mathematical relationship model to calculate the target pin force required to seal the current pressure P. The computational model can be represented as follows: .in, It can be a linear or nonlinear function, derived through theoretical calculations or experimental calibration. This is a preset safety margin factor, for example, 1.2. Assume it is calculated based on the model. =20N.

[0035] S3: Target Compression Displacement Calculation: The control system obtains the known linear coefficient k of the elastic force-applying component (coil spring), for example, k = 10 N / mm. Then, using the formula... Calculate the target displacement that the drive mechanism needs to continue pressing downwards after touching the seal ring. Substitute the values: =20N / (10N / mm)=2mm.

[0036] S4: Zero-point addressing: The control system controls the Z-axis drive mechanism (stepper motor) to drive the injection needle to descend at a certain speed. When the tip of the injection needle just touches the injection port sealing ring, the position detection sensor (zero-point detection unit) triggers a signal. After receiving the signal, the control system immediately marks the current coordinate value of the stepper motor as the "zero-point position".

[0037] S5: Precise Compression and Force Application: Starting from the "zero position" determined in step S4, the control system sends a command to the Z-axis drive mechanism, driving the injection needle to continue descending precisely by 2mm (i.e., ΔL calculated in step S3). After execution, the elastic force-applying component is precisely compressed by 2mm, and according to Hooke's Law, it applies a sealing force of 20N to the injection needle. Under the action of this force, the injection needle forms a reliable seal with the sealing gasket.

[0038] S6: Valve Path Switching for Sample Injection: With the injection needle under load (i.e., the sealing force remains constant), the control system switches the six-way valve from the bypass (Load) state to the analytical flow path (Inject) state. At this time, the injection needle is connected to the high-pressure flow path. Because the sealing force matches the system pressure, the system completes sample injection without leakage.

[0039] The control method in this embodiment transforms the complex force control problem into a high-precision displacement control problem. It has clear logic, is easy to implement using existing motor control systems, and offers high control accuracy and good stability.

[0040] Example 3

[0041] This embodiment provides a computer-readable storage medium on which a computer program is stored. When executed by a processor, the computer program can implement the pressure feedback adaptive needle insertion force control method for liquid chromatography autosampler as described in Embodiment 2. The storage medium can be any tangible medium that contains or stores the program, such as a hard disk, solid-state drive, flash memory card, optical disk, etc.

[0042] Example 4

[0043] This embodiment provides a liquid chromatography autosampler, which includes the pressure feedback adaptive needle insertion force control-based liquid chromatography autosampler as described in Embodiment 1. Due to its pressure sensing and adaptive force control capabilities, this autosampler exhibits higher reliability and lower consumable replacement frequency during long-term operation.

[0044] Example 5

[0045] This embodiment provides a liquid chromatograph that includes an autosampler as described in Example 4. Because of the use of this autosampler, the stability and repeatability of the overall analytical results are significantly improved, and the instrument's maintenance costs and lifespan are also optimized.

[0046] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. A method for controlling an automated liquid chromatograph based on pressure feedback, characterized in that, include: The real-time pressure value in the high-pressure flow path of a liquid chromatograph is obtained. The liquid chromatograph includes an injection needle and a Z-axis drive mechanism for driving the injection needle to move up and down in the vertical direction. Based on the real-time pressure value, determine the target sealing force required to maintain the seal under the current pressure; Based on the elastic coefficient of the elastic element connected in series between the Z-axis drive mechanism and the injection needle, the target sealing force is converted into the target displacement amount that the Z-axis drive mechanism needs to perform; The Z-axis drive mechanism is controlled to drive the injection needle to descend, and when a critical position is detected where the injection needle contacts the sealing assembly, the Z-axis drive mechanism is controlled to drive the injection needle to continue moving the target displacement from the critical position, so that the elastic element deforms and applies the target sealing force to the injection needle.

2. The method according to claim 1, characterized in that, The step of determining the target sealing force required to maintain the seal under the current pressure based on the real-time pressure value specifically includes: Based on the preset function model Determine the target sealing force, wherein The target sealing force, The real-time pressure value, The minimum critical force function required to maintain a seal, This is a preset safety margin factor greater than 1.

3. The method according to claim 1, characterized in that, The method further includes: While the injection needle maintains the applied target sealing force, the six-way valve is controlled to switch to the analytical flow path state.

4. A pressure feedback-based automatic liquid chromatography sampler control system, characterized in that, The system is used to implement the method according to any one of claims 1-3, the system comprising: The pressure monitoring unit is used to acquire the pressure value in the high-pressure flow path of the liquid chromatography system in real time; the zero-point detection unit is used to detect the critical position of the injection needle in contact with the sealing assembly. The control unit is electrically connected to both the pressure monitoring unit and the zero-point detection unit. The control unit is configured as follows: The target sealing force is determined based on the pressure value obtained by the pressure monitoring unit. The target displacement is determined based on the target sealing force and the elastic coefficient of the elastic element connected in series between the Z-axis drive mechanism and the injection needle. In response to the critical position detected by the zero-point detection unit, the Z-axis drive mechanism is controlled to drive the injection needle to continue moving the target displacement from the critical position, so that the elastic element deforms and applies the target sealing force to the injection needle.

5. The system according to claim 4, characterized in that, The control unit is also configured to operate according to a preset function model. Determine the target sealing force, wherein The target sealing force, The real-time pressure value, The minimum critical force function required to maintain a seal, This is a preset safety margin factor greater than 1.

6. The system according to claim 4, characterized in that, The control unit is also configured to control the six-way valve to switch to the analysis flow path state after the Z-axis drive mechanism applies the target sealing force.

7. An automated liquid chromatography sampler, characterized in that, Includes the system as described in any one of claims 4 to 6.

8. A liquid chromatograph, characterized in that, Includes the liquid chromatography autosampler as described in claim 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 3.

Images