Thermal desorption instrument

Abstract

The utility model provides a thermal desorption instrument which comprises a quantitative tube, a sampling end of the quantitative tube is connected with an injector, the injector is connected with a sample tube, a sample tube heating part is arranged in the middle of the sample tube, an injector heater is arranged outside the injector, and a sample outlet end of the quantitative tube is connected with a gas chromatograph. The thermal desorption instrument provided by the utility model is simple and reasonable in structure and strong in integrity, the full-automatic desorption analysis process of the thermal desorption instrument conforms to the national standard operation specification, quantitative sampling and quantitative sample injection are carried out on an air sample, manual operation is not needed, errors caused by manual operation and interference of temperature change on the sample during sample transfer are effectively solved, and the working efficiency is improved. The accuracy and the reliability of sample detection data analysis are improved, the applicability is good, and popularization and application are facilitated.

Description

Technical Field

[0001] This utility model relates to the field of thermal desorption technology, and more specifically, to a thermal desorption apparatus. Background Technology

[0002] Thermal desorption is a commonly used analytical instrument for analyzing volatile organic compounds (VOCs) in samples. It releases VOCs from the sample by heating it (thermal desorption). The desorbed sample is then introduced into a gas chromatograph (GC) with an inert carrier gas (such as nitrogen or helium) for separation and quantitative analysis. In GC, the components in the sample are separated based on the differences in their partition coefficients between the stationary and mobile phases.

[0003] However, the national standard operating procedures for some currently used thermal desorption instruments have high requirements for human operation, which can easily lead to problems such as human error and temperature changes during sample transfer that can interfere with the sample, thus reducing the accuracy and reliability of sample detection data analysis. Utility Model Content

[0004] Therefore, the purpose of this utility model is to design a thermal desorption instrument whose fully automatic desorption analysis process conforms to national standard operating procedures. It performs quantitative sampling and quantitative injection of air samples without human intervention, thereby solving the errors caused by human operation and the interference of temperature changes during sample transfer, thus improving the accuracy and reliability of sample detection data analysis.

[0005] This utility model provides a thermal desorption instrument, comprising: a quantitative tube, a syringe connected to the sampling end of the quantitative tube, a sample tube connected to the syringe, a sample tube heating element (preferably a heating rod) provided in the middle of the sample tube, a syringe heater (preferably a silicone heating plate) provided on the outside of the syringe, and a gas chromatograph (GC) connected to the sample outlet end of the quantitative tube.

[0006] In the heating preparation state (initial state), the sample tube heating element heats the sample tube, while the syringe is kept warm by the syringe heater to prevent the sample from condensing in the glass syringe.

[0007] After thermal desorption, the sample gas is quantified and then introduced into a gas chromatograph (GC) for separation and quantitative analysis. In the gas chromatograph, the components in the sample are separated based on the difference in their partition coefficients between the stationary phase and the mobile phase, and the separated components are detected sequentially.

[0008] Preferably, the metering tube adopts the gas measuring cylinder method, which is based on the principle of gas volume change in a closed system. The gas volume is calculated by the principle of communicating vessels and the ideal gas law, which is simple to operate and low in cost.

[0009] This invention optimizes and improves the thermal desorption instrument by designing a sampling structure in which the sample tube is connected to the syringe and the syringe is connected to the quantitative tube. This avoids sampling and injection errors caused by human operation. Heating devices are set in the sample tube and the syringe respectively to avoid the interference of temperature changes on the sample during sample transfer, thereby improving the accuracy and stability of the sample flow rate during sampling and injection.

[0010] Furthermore, the sample tube is connected to a purge channel, a purge solenoid valve is provided on the connecting pipe between the purge channel and the sample tube, a switching valve (preferably a six-way switching valve) is provided on the connecting pipe between the sample tube and the syringe, a negative pressure pump is connected to the switching valve, and an injection valve (preferably a six-way injection valve) is provided on the connecting pipe between the quantitative tube and the gas chromatograph.

[0011] Specifically, the sample tube is heated using a heating rod. Once the sample has completely precipitated, the purge solenoid valve is opened, and the precipitated sample is blown into the syringe (preferably 100 ml) at a set flow rate and time. Simultaneously, the syringe is kept warm by a silicone heating plate to prevent sample condensation in the glass syringe. The six-way switching valve is opened, and the negative pressure pump is activated at the set flow rate and time to quantitatively measure the sample in the syringe through a quantitative tube. The sample flow rate is balanced, and the quantified sample is then introduced into the gas chromatograph (GC) for analysis via the injection valve.

[0012] Furthermore, the sample outlet of the quantitative tube is connected to an activation channel, an activation solenoid valve is provided on the connecting pipe between the quantitative tube and the activation channel, and an inert gas interface is provided at the gas inlet of the activation channel.

[0013] This thermal desorption instrument has a split recovery function, and after the sample is injected, the nitrogen gas can be drawn out and discharged by a negative pressure pump and recovered.

[0014] Specifically, after the injection is completed, the activation solenoid valve is opened, the six-way injection valve is reset, the six-way switching valve is opened, and nitrogen gas is blown into the syringe through the metering tube. Then, the nitrogen gas is drawn out and vented by the negative pressure pump. This process can be repeated multiple times as needed. The nitrogen gas pressure is controlled by the first flow control valve.

[0015] Furthermore, the sample tube is connected to a calibration channel, and a calibration solenoid valve for injecting an internal standard is provided on the connecting pipe between the sample tube and the calibration channel.

[0016] When entering the calibration state, open the calibration solenoid valve and inject the internal standard into the sample tube.

[0017] An internal standard is a pure substance of known mass, free of impurities, added to the sample to be tested. The amount of this pure substance is used as a standard to compare and determine the content of the analyte. The internal standard is a pure substance not originally present in the sample, preventing interference with the test results and ensuring the accuracy of the content determination.

[0018] Furthermore, the sample tube heating element and the syringe heater are respectively connected to temperature sensors for controlling the temperature of the sample tube heating element and the temperature of the syringe heater.

[0019] Preferably, the temperature sensor is a PT100 type temperature sensor. The PT100 type temperature sensor is an instrument that converts temperature variables into a standardized, transmittable output signal, which can be used for the measurement and control of temperature parameters in thermal desorption processes. The PT100 type temperature sensor consists of two parts: a sensor and a signal converter. The sensor is mainly a thermocouple or resistance temperature detector (RTD); the signal converter mainly consists of a measurement unit, a signal processing unit, and a conversion unit.

[0020] The temperature sensor collects the temperature signal and uploads it to the control system. Based on the received temperature signal, the control system sends a control signal to open or reset the corresponding valve.

[0021] Furthermore, a first flow control valve is provided between the negative pressure pump and the switching valve, a second flow control valve and a third flow control valve are provided between the activation solenoid valve and the purging solenoid valve, and a pressure control valve is provided between the second flow control valve and the third flow control valve.

[0022] The pressure in the nitrogen suction and venting pipeline is controlled by the first flow control valve; the flow rate in the purging pipeline is adjusted by the second flow control valve, and the pressure in the purging pipeline is adjusted by the pressure control valve.

[0023] Preferably, a flow sensor is installed in the pipeline between the switching valve, the activation solenoid valve and the purging solenoid valve, and a pressure sensor is installed in the pipeline at the negative pressure pump. The flow sensor and the pressure sensor collect flow signals and pressure signals respectively and upload them to the control system. The control system sends control signals to control the first flow control valve, the second flow control valve, the third flow control valve and the pressure control valve to perform corresponding opening or resetting actions.

[0024] Furthermore, the first flow control valve, the second flow control valve, and the third flow control valve are each connected to a gas mass flow controller for accurate and rapid measurement of minute gas flow rates. The gas mass flow controller employs a capillary thermoelectric sensor.

[0025] Specifically, the gas mass flow controller is connected to the control system, and the precise and rapid measurement of minute gas flow rates by the gas mass flow controller further improves the flow control accuracy.

[0026] The measurement accuracy of capillary thermoelectric sensors is unaffected by temperature and pressure, can be installed in any orientation, is suitable for toxic and corrosive gases, and can operate at a maximum pressure of 1500 Ps.

[0027] Furthermore, there are multiple sample tubes, which are placed on a sample tray. A photoelectric sensor for non-contact monitoring of the sample tube sampling and injection process is provided at the upper center of the sample tray.

[0028] The sample tray can hold multiple sample tubes, allowing for separate thermal desorption operations and continuous sample introduction. A photoelectric sensor (preferably a through-beam photocoupler sensor) monitors the sampling and injection progress of each sample tube, avoiding human error, improving sampling and injection efficiency, and thus improving analysis efficiency.

[0029] The photoelectric sensor converts the optical signals from multiple sample tubes into photoelectric signals and uploads them to the control system. The control system then controls the sampling and injection process of the corresponding sample tubes.

[0030] Furthermore, the sample disk is a rotatable turntable structure, and multiple sample tubes are placed at uniformly spaced arcs along the circumference of the sample disk.

[0031] The rotary sample tray combines the advantages of rotary and pulsed sample introduction, enabling rapid and accurate sample introduction operations. It allows for unattended operation, saving labor costs. The high sample introduction speed allows for the injection of large quantities of samples in a short time, with accurate and repeatable sample volumes, reducing human error and ensuring the reliability and accuracy of analytical results.

[0032] Compared with the prior art, the beneficial effects of this utility model are:

[0033] The thermal desorption instrument provided by this utility model has a simple and reasonable structure and strong overall integrity. The fully automatic desorption analysis process of this thermal desorption instrument conforms to the national standard operating procedures. It can quantitatively sample and inject air samples without human operation, effectively solving the errors of human operation and the interference of temperature changes during sample transfer. It improves the accuracy and reliability of sample detection data analysis, has good applicability, and has broad prospects for promotion and application. Attached Figure Description

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] In the attached diagram:

[0036] Figure 1 This is an initial state diagram of the thermal desorption apparatus according to an embodiment of this utility model;

[0037] Figure 2 This is a calibration state diagram of the thermal desorption apparatus according to an embodiment of this utility model;

[0038] Figure 3 This is a purging state diagram of the thermal desorption apparatus according to an embodiment of the present invention;

[0039] Figure 4 This is a quantitative state diagram of the thermal desorption apparatus according to an embodiment of this utility model;

[0040] Figure 5 This is a diagram showing the sample introduction state of the thermal desorption apparatus according to an embodiment of this utility model;

[0041] Figure 6 , Figure 7 This is an activation state diagram of the thermal desorption apparatus according to an embodiment of this utility model.

[0042] The markings in the attached figure are as follows:

[0043] 1. Six-way switching valve; 2. Quantitative tube; 3. Six-way injection valve; 4. First flow control valve; 5. Negative pressure pump; 6. Sample tube; 7. 100ml syringe; 8. Syringe heater; 9. Activation solenoid valve; 10. Calibration solenoid valve; 11. Purge solenoid valve; 12. Second flow control valve; 13. Third flow control valve; 14. Pressure control valve; 15. Gas chromatograph. Detailed Implementation

[0044] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0045] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0046] It should be understood that although the terms first, second, and third may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0047] Example

[0048] This utility model embodiment provides a thermal desorption apparatus, such as... Figure 1 As shown, the sampling end of the quantitative tube 2 is connected to a 100ml syringe 7, which is connected to a sample tube 6. A sample tube heating rod is located in the middle of the sample tube 6. A syringe heater 8, made of a silicone heating plate, is located on the outside of the 100ml syringe 7. The dispensing end of the quantitative tube 2 is connected to a gas chromatograph (GC) 15. The sample tube heating rod and syringe heater 8 are respectively connected to temperature sensors used to control the temperature of the heating element in the sample tube and the temperature sensor in the syringe heater. The temperature sensor is a PT100 type temperature sensor, which consists of two parts: a sensor and a signal converter. The sensor is mainly a thermocouple or resistance temperature detector (RTD); the signal converter mainly consists of a measurement unit, a signal processing and conversion unit. The temperature sensor uploads the collected temperature signal to the control system. Based on the received temperature signal, the control system sends a control signal to control the corresponding valve to open or reset.

[0049] In the heating preparation state (initial state), the sample tube heating rod heats the sample tube 6, while the 100ml syringe 7 is kept warm by the syringe heater 8 to prevent the sample from condensing in the glass syringe. After thermal desorption, the sample gas is quantified and introduced into the gas chromatograph 15 for separation and quantitative analysis. In the gas chromatograph, the components in the sample are separated based on the difference in their partition coefficients between the stationary and mobile phases, and the separated components are detected sequentially. The sample tube 6 is connected to the calibration channel, and a calibration solenoid valve 10 for injecting internal standard is installed on the connecting pipe between the sample tube 6 and the calibration channel. When entering the calibration state, the calibration solenoid valve 10 is opened to inject the internal standard into the sample tube 6. The internal standard is a pure substance that is not originally present in the sample, avoiding interference with the detection results and ensuring the accuracy of the content determination.

[0050] Sample tube 6 is connected to a purge channel. A purge solenoid valve 11 is installed on the connecting line between the purge channel and sample tube 6. A six-way switching valve 1 is installed on the connecting line between sample tube 6 and 100ml syringe 7. The six-way switching valve 1 is connected to a negative pressure pump 5. A six-way injection valve 3 is installed on the connecting line between quantitative tube 2 and gas chromatograph 15. After sample tube 6 is heated with a heating rod, when the sample in sample tube 6 has completely precipitated, the purge solenoid valve 11 is opened, and the precipitated sample is blown into 100ml syringe 7 at a set flow rate and time. At the same time, 100ml syringe 7 is kept warm by a silicone heating plate to prevent sample condensation in the glassy 100ml syringe 7. The six-way switching valve 1 is opened, and the negative pressure pump 5 is opened at a set flow rate and time to quantitatively measure the sample in 100ml syringe 7 through quantitative tube 2, balancing the sample flow. The quantified sample is then injected into gas chromatograph 15 through six-way injection valve 3 for detection and analysis.

[0051] In this embodiment, multiple sample tubes 6 are continuously monitored. These sample tubes 6 are placed on a rotatable, turntable-shaped sample disk, with evenly spaced arcs along the circumference of the disk. A through-beam photoelectric sensor is positioned at the top center of the sample disk for non-contact monitoring of the sample tube sampling and injection process. The sample disk allows for thermal desorption of the multiple sample tubes 6, enabling continuous sample injection. The through-beam photoelectric sensor converts the optical signals from the sampling and injection of the multiple sample tubes 6 into photoelectric signals and uploads them to the control system. The control system then controls the sampling and injection process of the corresponding sample tubes 6.

[0052] The sample outlet of the quantitative tube 2 is connected to the activation channel. An activation solenoid valve 9 is installed on the connecting pipe between the quantitative tube 2 and the activation channel, and an inert gas interface is installed at the inlet of the activation channel. After the sample injection is completed, the activation solenoid valve 9 is opened, the six-way injection valve 3 is reset, the six-way switching valve 1 is opened, and nitrogen gas is blown into the 100ml syringe 7 through the quantitative tube 2. Then, the nitrogen gas is drawn out and vented by the negative pressure pump 5. The nitrogen gas pressure is controlled by the first flow control valve 4.

[0053] A first flow control valve 4 is installed between the negative pressure pump 5 and the six-way switching valve 1. A second flow control valve 12 and a third flow control valve 13 are installed between the activation solenoid valve 9 and the purge solenoid valve 11. A pressure control valve 14 is installed between the second and third flow control valves 12 and 13. The first flow control valve 4 controls the pressure on the nitrogen exhaust pipeline; the second flow control valves 12 and 13 regulate the flow rate in the purge pipeline; and the pressure control valve 14 regulates the pressure in the purge pipeline. Flow sensors are installed in the pipelines between the six-way switching valve 1, the activation solenoid valve 9, and the purge solenoid valve 11, and a pressure sensor is installed in the pipeline at the negative pressure pump 5. The flow and pressure sensors collect flow and pressure signals, respectively, and upload them to the control system. The control system sends control signals to control the first flow control valve 4, the second flow control valve 12, the third flow control valve 13, and the pressure control valve 14 to perform corresponding opening or resetting actions. The first flow control valve 4, the second flow control valve 12, and the third flow control valve 13 are connected to a gas mass flow controller for precise and rapid measurement of small gas flow rates. The gas mass flow controller is connected to the control system, enabling precise and rapid measurement of minute gas flow rates.

[0054] The thermal desorption apparatus of this utility model embodiment mainly includes the following operating procedures in practical applications:

[0055] 1. Enter the heating preparation state (initial state, such as...) Figure 1 As shown): The sample tube 6 is heated, and the 100ml syringe 7 is kept warm by the syringe heater 8 to prevent the sample from condensing in the glassy 100ml syringe 7. The temperature is monitored by a PT100 temperature sensor.

[0056] 2. Enter calibration state (e.g.) Figure 2 (As shown): Open the calibration solenoid valve 10 and inject the internal standard into the sample tube 6;

[0057] 3. Enter purging mode (e.g.) Figure 3 (As shown): After the sample material in the sample tube 6 has completely precipitated, the purge solenoid valve 11 is opened, and the precipitated sample is blown into the 100ml syringe 7 at the set flow rate and time. The flow rate of the purge line is adjusted by the second flow control valve 12 and the third flow control valve 13, and the pressure of the purge line is adjusted by the pressure control valve 14.

[0058] 4. Entering a quantitative state (e.g.) Figure 4 (As shown): Open the six-way switching valve 1, and at the same time turn on the negative pressure pump 5 according to the set flow rate and time, and quantitatively measure the sample in the 100ml syringe 7 through the quantitative tube 2 to balance the sample flow rate;

[0059] 5. Enter the sample injection state (e.g.) Figure 5(As shown): Open the six-way injection valve 3 to bring the quantified sample into the gas chromatograph 15 for analysis; by repeatedly switching the six-way injection valve 3, a single sample can be injected multiple times;

[0060] 6. Entering the activated state (e.g.) Figure 6 , Figure 7 As shown): After the injection is completed, open the activation solenoid valve 9, reset the six-way injection valve 3, open the six-way conversion valve 1, blow nitrogen into the 100ml syringe 7 through the quantitative tube 2, and then the negative pressure pump 5 will draw out the nitrogen and vent it. This process can be repeated multiple times as needed; the nitrogen extraction pressure is controlled by the first flow control valve 4.

[0061] The thermal desorption instrument in this embodiment has a simple and reasonable structure with strong overall integrity. The fully automatic desorption analysis process of this thermal desorption instrument complies with national standard operating procedures. It performs quantitative sampling and quantitative injection of air samples without human operation, effectively solving the errors caused by human operation and the interference of temperature changes during sample transfer. This improves the accuracy and reliability of sample detection data analysis and has good applicability.

[0062] The technical solution of this utility model has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the protection scope of this utility model is obviously not limited to these specific embodiments. Without departing from the principle of this utility model, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of this utility model.

[0063] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A thermal desorption apparatus, characterized in that, include: A quantitative tube is provided, with a syringe connected to the sampling end of the quantitative tube, a sample tube connected to the syringe, a sample tube heating element provided in the middle of the sample tube, a syringe heater provided on the outside of the syringe, and a gas chromatograph connected to the dispensing end of the quantitative tube.

2. The thermal desorption apparatus according to claim 1, characterized in that, The sample tube is connected to a purge channel, and a purge solenoid valve is installed on the connecting pipe between the purge channel and the sample tube. A switching valve is installed on the connecting pipe between the sample tube and the syringe, and a negative pressure pump is connected to the switching valve. An injection valve is installed on the connecting pipe between the quantitative tube and the gas chromatograph.

3. The thermal desorption apparatus according to claim 2, characterized in that, The sample outlet of the quantitative tube is connected to an activation channel, and an activation solenoid valve is installed on the connecting pipe between the quantitative tube and the activation channel. An inert gas interface is installed at the gas inlet of the activation channel.

4. The thermal desorption apparatus according to claim 1, characterized in that, The sample tube is connected to a calibration channel, and a calibration solenoid valve for injecting an internal standard is provided on the connecting pipe between the sample tube and the calibration channel.

5. The thermal desorption apparatus according to claim 1, characterized in that, The sample tube heating element and the syringe heater are respectively connected to temperature sensors for controlling the temperature of the sample tube heating element and the temperature of the syringe heater.

6. The thermal desorption apparatus according to claim 3, characterized in that, A first flow control valve is provided between the negative pressure pump and the switching valve, a second flow control valve and a third flow control valve are provided between the activation solenoid valve and the purging solenoid valve, and a pressure control valve is provided between the second flow control valve and the third flow control valve.

7. The thermal desorption apparatus according to claim 6, characterized in that, The first flow control valve, the second flow control valve, and the third flow control valve are respectively connected to a gas mass flow controller for accurate and rapid measurement of small gas flow rates. The gas mass flow controller adopts a capillary thermoelectric sensor.

8. The thermal desorption apparatus according to claim 1, characterized in that, The sample tubes are multiple and are placed on a sample tray. A photoelectric sensor for non-contact monitoring of the sample tube sampling and injection process is provided at the upper center of the sample tray.

9. The thermal desorption apparatus according to claim 8, characterized in that, The sample disk is a rotatable turntable structure, and multiple sample tubes are placed at uniformly spaced arcs along the circumference of the sample disk.

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