Method and device for real-time detection of contamination of chromatographic columns by high-concentration samples

Abstract

The present invention relates to a method and detection equipment for real-time detection of contamination of a chromatographic column carrying a high-concentration sample. The method aims to solve the problem in the prior art that a high-concentration sample contaminates a chromatographic column, resulting in the inability to detect subsequent samples normally or inaccurate detection values. The method of the present invention includes: signal acquisition, conditioning, conversion, calculation, and analysis of the acquired signal to control the heating of the chromatographic column and the opening and closing of the airway under the corresponding state timing. The advantages are: automatic detection of high concentrations to prevent the accuracy of subsequent sample analysis caused by contamination of the chromatographic column by high-concentration samples; processing and conversion of different signals generated by chromatographs of different manufacturers and different models, thereby achieving real-time detection; when high-concentration contamination is detected, the functions of the injector except purging are frozen to eliminate the problem of cross-contamination of the injector's own pipelines.

Description

Technical Field

[0001] The present invention relates to the field of sample detection equipment, in particular to a method and detection equipment for real-time detection of contamination of a chromatographic column by a high-concentration sample. Background Art

[0002] A gas chromatography column is a column in which gas is introduced by a carrier gas and passed through a chromatographic column with different retention properties for the components in the mixture to be detected, separating the components and then sequentially introducing them into a detector to obtain detection signals for each component. By comparing the order in which the components are introduced into the detector, the components can be identified, and the content of each component can be calculated based on the peak height or peak area. Chromatography uses a chromatographic column to first separate the mixture, and then uses a detector to detect the separated components in sequence. In this type of technology, chromatographic column aging involves raising the column temperature to 30-50 degrees below the maximum operating temperature of the column while passing carrier gas, and then performing high-temperature baking to remove some organic matter remaining in the column.

[0003] In recent years, with increasing attention paid to environmental pollution across all industries, relevant departments have issued national standards to monitor environmental pollution levels, specifically the detection of volatile organic compounds (VOCs) in both organized and unorganized emissions. Currently, most testing units use modified or dedicated gas chromatographs for this purpose. Due to the uncertainty surrounding the composition and concentration of gases, high concentrations of contaminated gases entering the GC can contaminate the chromatographic column. When a chromatographic column becomes contaminated, the GC oven temperature must be raised to "age" the column and eliminate the contamination.

[0004] The widespread use of gas autosamplers has significantly reduced the tediousness of manual injection, almost achieving a state of unattended operation. However, when high-concentration samples enter the gas chromatograph, they cannot be detected in time, and the column oven temperature cannot be raised to "age" the column. This causes subsequent gas samples to enter the contaminated column, directly affecting the detection and accuracy of subsequent gas samples. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem in the prior art that when analyzing gas by gas chromatography, high concentration samples contaminate the chromatographic column, resulting in the inability to detect the samples normally or inaccurate detection values.

[0006] The specific solution of the present invention is: a method for real-time detection of contamination of a chromatographic column carrying a high-concentration sample, comprising the following steps:

[0007] (1) Signal acquisition: The concentration value of the sample gas is reflected in the microvoltage signal in the output signal of the gas chromatograph detector. The microvoltage signal in the gas chromatograph signal output by the detector is intercepted, and the signal used to feedback the sample concentration is intercepted from the gas chromatograph output signal to obtain the microvoltage information A;

[0008] (2) Signal conditioning: The micro-voltage information A is amplified in multiple stages through an integrated operational amplifier to form micro-voltage information B, and the micro-voltage information B is amplified through a filter amplifier to form micro-voltage information C;

[0009] (3) Signal conversion: The micro-voltage information C is converted into a digital signal D via an AD converter, converting the analog signal into a digital signal;

[0010] (4) Signal filtering and calculation: The signal filtering adopts the pulse interference-proof average filtering algorithm. The digital signal D is connected to the data display device on the digital circuit. The signal filtering adopts the pulse interference-proof average filtering algorithm. The pulse interference-proof average algorithm first compares N sampling signals, finds the maximum and minimum values, eliminates them, and then performs average calculation to calculate the sample concentration value E, E = (A0 + A1 + ... A20) - AMAX - AMIN) / 19; where A0-A20 represents the sampling value; AMAX represents the maximum sampling value; AMIN represents the minimum sampling value; 19 represents the number of sampling values;

[0011] (5) Monitor sample concentration: Based on the stability of the monitoring baseline, when the sample concentration is greater than or equal to the alarm concentration, the automatic sampler will stop and alarm. At the same time, the gas chromatography column oven temperature will be increased automatically or manually. The temperature will be increased by 20°C again to age the chromatographic column and the injection line will be purged until the sample concentration returns to normal and the baseline returns to stability. The large fluctuations here mainly refer to fluctuations in the non-horizontal state that are visible to the naked eye.

[0012] In step (1), a shielded twisted pair is used to intercept the micro-voltage signal.

[0013] In step (5), the standard for the sample concentration value to return to normal is that the electrical signal gradually approaches the original zero value and no longer has large fluctuations, that is, the positive and negative fluctuations are less than 20 microvolts.

[0014] The present application also relates to a device for real-time detection of contamination of a chromatographic column carrying a high-concentration sample, comprising an information monitoring and transmission mechanism, a control mechanism, a chromatographic gas path mechanism, and an injector gas path mechanism connected to the inlet of the chromatographic gas path mechanism; wherein the chromatographic gas path mechanism comprises a chromatographic column, a temperature-controlled box for accommodating the chromatographic column, and a detector connected to the chromatographic column; the information monitoring and transmission mechanism comprises a signal amplifier board, a signal converter, and a chromatographic workstation in sequence along the direction of electrical information transmission, the input end of the signal amplifier board is connected to the detector, and the output end of the signal amplifier board is also connected to a signal acquisition board of the control mechanism; the control mechanism comprises a main control board, the input end of the main control board is connected to the signal acquisition board, and the output end of the main control board is connected to an injector host computer and the opening and closing switches corresponding to each component in the injector gas path mechanism; the injector gas path mechanism comprises a sampling circuit and a purge circuit, which are connected via an injection valve and a two-position three-way solenoid valve, and are selectively opened, wherein the sampling circuit comprises a container for loading sampling gas and connected to the injection valve, and a vacuum pump, wherein the purge circuit comprises an inert gas container and a pressure-stabilizing valve and a flow-stabilizing valve connected thereto.

[0015] The sampling circuit includes at least two sampling gas containers, and the outlet of each sampling gas container is connected in parallel to the inlet of the selection valve as a branch pipeline, and the outlet of the selection valve is connected to the injection valve.

[0016] An electric heating device is provided in the temperature control box, and a circuit of the electric heating device is connected to the output end of the main control board.

[0017] The detector and the signal amplifier board are connected via two shielded twisted cables, forming a two-wire loop with a single twist at its midpoint. While twisted-pair technology is currently available, its use in this technology effectively eliminates interference and improves measurement accuracy, offering beneficial results. An air block is provided between the vacuum pump's air inlet and the two-position, three-way valve.

[0018] The signal amplifier board is provided with an LC filter circuit a, an input signal amplifier circuit b, a signal conditioning circuit c, a primary filter circuit d and a secondary filter circuit e in sequence, wherein the input signal amplifier circuit b and the signal conditioning circuit c are each connected in parallel with an independent branch filter circuit f.

[0019] The beneficial effects of the present invention are:

[0020] High concentration automatic detection prevents the accuracy of subsequent sample analysis from being affected by high concentration sample contamination of the chromatographic column;

[0021] It can process and convert different signals generated by chromatographs of different manufacturers and models, thus achieving real-time detection;

[0022] When high-concentration contamination is detected, all functions of the injector except purge are frozen to eliminate cross-contamination problems in the injector's own pipelines;

[0023] The temperature is automatically raised to age the chromatographic column, and the process is simple and easy to operate. When the sample concentration signal reaches the user-set alarm value, the injector operating software automatically freezes all functions and buttons except the pipeline purge to prevent cross-contamination of the autosampler pipeline due to misoperation. The injector can only be operated normally after the chromatographic column is aged and the baseline is stabilized again.

[0024] The anti-pulse interference average algorithm first compares N sampled signals, finds the maximum and minimum values, removes them, and then performs average calculation. This can effectively eliminate the interference of interference signals on useful signals. This algorithm has the characteristics of fast calculation speed and strong anti-interference ability. After the signal is filtered, the circuit can be used to calculate the sample concentration value;

[0025] The voltage reference circuit's temperature drift can reach 5ppm, ensuring that the device's measurement impact within normal ambient temperature fluctuations does not exceed 200ppm. Shielded twisted-pair cables introduce signals into the device, enhancing its immunity to interference. Since the conditions of the two lines are identical, the total interference current, I, equals zero. Setting a reasonable twist length eliminates interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a workflow diagram of the present invention;

[0027] Figure 2 It is the overall structural diagram of the present invention;

[0028] Figure 3 It is a schematic diagram of the control mechanism structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the gas path structure of the sample injector in the present invention;

[0030] Figure 5 This is a schematic diagram of the information monitoring and transmission mechanism structure of the present invention;

[0031] Figure 6 This is a schematic diagram of the structure of the chromatographic gas path mechanism in the present invention;

[0032] Figure 7 This is a schematic diagram of the circuit structure of the signal amplifier board in the present invention;

[0033] Figure 8 is a schematic diagram of an AD converter in the present invention;

[0034] Figure 9It is a flow chart of the sampling stage;

[0035] Figure 10 It is a schematic diagram of the injection stage;

[0036] Figure 11 It is a schematic diagram of the purge stage;

[0037] Figure 12 This is a schematic diagram of the connection of double-shielded twisted cables;

[0038] Figure 13 It is a schematic diagram of the structure of the gas chromatography column and the temperature control box;

[0039] 1. Control mechanism; 2. Injector gas path mechanism; 3. Information monitoring and transmission mechanism; 4. Chromatographic gas path mechanism; 5. Temperature control box; 6. Electric heating device; 7. Thermometer;

[0040] a. LC filter circuit; b. Input signal amplification circuit; c. Signal conditioning circuit; d. Primary filter circuit; e. Secondary filter circuit; f. Branch filter circuit; g. Signal input;

[0041] 101. Sampler host computer; 102. Main control board; 103. Signal acquisition board;

[0042] 201. Vacuum pump; 202. Vacuum pump outlet; 203. Vacuum pump inlet; 204. Exhaust port; 205. Air block; 206. Two-position three-way solenoid valve; 207. Selector valve; 208. Standard gas container; 209. Injection valve; 210. Flow stabilizing valve; 211. Pressure stabilizing valve; 212. Inert gas inlet;

[0043] 301. Chromatographic workstation; 302. Signal converter; 303. Signal amplifier board;

[0044] 401. First carrier gas inlet; 402. Second carrier gas inlet; 403. Detector; 404. Chromatographic column;

[0045] Figure 12 In, US is the signal voltage, and RS is the load impedance. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0047] Example 1

[0048] A method for real-time detection of contamination of a chromatographic column by a high-concentration sample comprises the following steps:

[0049] (1) Signal acquisition: The concentration value of the sample gas is reflected in the micro-voltage signal in the output signal of the gas chromatograph detector 403. The micro-voltage signal in the gas chromatograph signal output by the detector 403 is intercepted, and the signal used to feedback the sample concentration is intercepted from the gas chromatograph output signal to obtain the micro-voltage information A;

[0050] (2) Signal conditioning: The micro-voltage information A is amplified in multiple stages after passing through an integrated operational amplifier to form micro-voltage information B. The micro-voltage information B is then amplified through a filter amplifier to form micro-voltage information C.

[0051] (3) Signal conversion: The micro-voltage information C is converted into a digital signal D via an AD converter, converting the analog signal into a digital signal;

[0052] (4) Signal filtering and calculation: The signal filtering adopts the pulse interference-proof average filtering algorithm. The digital signal D is connected to the data display device on the digital circuit. The signal filtering adopts the pulse interference-proof average filtering algorithm. The pulse interference-proof average algorithm first compares N sampling signals, finds the maximum and minimum values, eliminates them, and then performs average calculation to calculate the sample concentration value E, E=(A0+A1+…A20-AMAX-AMIN) / 19; where A0-A20 represents the sampling value; AMAX represents the maximum sampling value; AMIN represents the minimum sampling value; 19 represents the number of sampling values;

[0053] (5) Monitor the sample concentration value: Based on the stability of the monitoring baseline, when the sample concentration value is greater than or equal to the alarm concentration value, the automatic sampler will stop and alarm, and automatically or manually intervene to increase the temperature of the gas chromatography column 404 oven, and then increase the temperature by 20℃ again to age the chromatographic column 404, and purge the injection pipeline until the sample concentration value returns to normal and the baseline returns to stability.

[0054] In step (1), a shielded twisted pair is used to intercept the micro-voltage signal. The shielded twisted pair includes two shielded conductors twisted at least once to shield interference signals.

[0055] In step (5), the standard for the sample concentration value to return to normal is that the electrical signal gradually approaches the original zero value and no longer has large fluctuations.

[0056] The present application also relates to a device for real-time detection of contamination of a chromatographic column carrying a high-concentration sample, comprising an information monitoring and transmission mechanism 3, a control mechanism 1, a chromatographic gas path mechanism 4, and an injector gas path mechanism 2 connected to the inlet of the chromatographic gas path mechanism 4; wherein the chromatographic gas path mechanism 4 comprises a chromatographic column 404, a temperature control box for accommodating the chromatographic column 404, and a detector 403 connected to the chromatographic column 404; the information monitoring and transmission mechanism 3 comprises a signal amplifying board 303, a signal converter 302, and a chromatographic workstation 301 in sequence along the direction of electrical information transmission, the input end of the signal amplifying board 303 is connected to the detector 403, and the output end of the signal amplifying board 303 is also connected to the control mechanism 1. The signal acquisition board 103 of the mechanism 1; the control mechanism 1 includes a main control board 102, the input end of the main control board 102 is connected to the signal acquisition board 103, and the output end of the main control board 102 is connected to the injector host computer 101 and the opening and closing switches corresponding to the components in the injector gas path mechanism 2; the injector gas path mechanism 2 includes a sampling circuit and a purge circuit that are selectively opened and connected via an injection valve 209 and a two-position three-way solenoid valve 206, wherein the sampling circuit includes a container loaded with sampling gas and connected to the injection valve 209, and a vacuum pump 201, wherein the purge circuit includes an inert gas container and a pressure-stabilizing valve 211 and a flow-stabilizing valve 210 connected thereto.

[0057] The sampling circuit includes at least two gas sampling containers. The outlet of each container serves as a branch line connected in parallel to the inlet of selector valve 207, which in turn connects to injection valve 209. An electric heater 6 is installed within the temperature control box 5, its circuit connected to the output of the main control board 102. The detector 403 and the signal amplifier board 303 are connected via two shielded twisted cables, forming a two-wire circuit. An air block 205 is installed between the air inlet of the vacuum pump 201 and the two-position three-way valve.

[0058] The signal amplifier board 303 is provided with an LC filter circuit a, an input signal amplifier circuit b, a signal conditioning circuit c, a primary filter circuit d and a secondary filter circuit e in sequence, wherein the input signal amplifier circuit b and the signal conditioning circuit c are each connected in parallel with an independent branch filter circuit f.

[0059] The electric injection valve 209, also known as an electric rotary valve or electric rotary valve, is primarily controlled by a stepper motor and is used for automated sample collection, injection, or flow path switching. The inert flow path of the electric injection valve 209 is suitable for various corrosive samples, and the internal materials of the valve body are matched to each other to form an effective seal and prevent leakage.

[0060] During operation, the injector works as follows:

[0061] The gas injector pushes each set of fixed volume sample gas into the chromatographic analysis with carrier gas in a process injection mode, that is, sampling, injection, and then waiting for the end of the chromatographic analysis to sample and inject the next sample.

[0062] During the sampling process: Fill the sample loop with sample in preparation for injection. Selector valve 207 switches to connect to the container, injection valve 209 switches to the sampling state and connects to the sample loop, and the two-position three-way solenoid valve 206 switches to connect to the flow path of vacuum pump 201. Vacuum pump 201 operates for a certain time calculated by the program and then stops, allowing the sample to fill the sample loop.

[0063] During the injection process: the injection valve 209 is switched to connect the carrier gas to the quantitative loop, and the sample is pushed into the gas chromatograph for analysis. When the substance passes through the detector 403, a voltage signal is generated and displayed on the workstation in the form of a spectrum after passing through the signal amplifier and signal converter 302.

[0064] During the purge process: when the sample enters the detector 403, the signal acquisition board 103 detects that the voltage signal of the detector 403 after passing through the signal amplification board 303 exceeds the set voltage value, the injector will alarm, freeze other functions and start the purge function of the injector, using inert gas to purge the contaminated pipeline. At the same time, the chromatographic column 404 oven is started to automatically heat up.

[0065] As described above, the injector operates on the principle that when the response voltage of a sample entering detector 403 falls below the set alarm voltage, the injector sequentially samples, injects, and analyzes each sample until all samples have been processed. If a sample concentration is too high—that is, if the response voltage of a sample passing through detector 403 exceeds the set alarm voltage—the injector generates an alarm, halts all operations, and prompts the user to remove the current sample and execute the purge function. Except for the purge function, all other operating buttons are frozen to prevent user error. Simultaneously, a signal is output to activate the chromatographic column heating oven. If a high-concentration sample contaminates the chromatographic column 404, the response voltage of detector 403 will fluctuate significantly for a period of time. As the column temperature rises over time, the electrical signal gradually approaches its original zero value, or baseline. Once the signal acquisition board 103 in the injector detects that the electrical signal has remained stable at zero for a certain period of time, it unfreezes the injector interface, allowing the injector to continue operating until all samples have been processed.

[0066] During the process, the device is equipped with RS232 and Ethernet communication interfaces, and any communication method can be used to send the measured sample concentration value to the monitoring software.

[0067] During this process, the monitoring software displays the current sample concentration and allows for setting alarm levels. When the sample concentration reaches or exceeds the alarm level, the autosampler shuts down and issues an alarm. Simultaneously, the temperature of the gas chromatograph column 404 oven is raised, either automatically or manually, to "age" the column and purge the injection line in preparation for subsequent sample injections. Furthermore, when the sample concentration reaches the user-set alarm level, the autosampler operating software automatically freezes all functions and buttons, except for the line purge, to prevent cross-contamination of the autosampler line caused by misoperation. Normal operation of the autosampler will resume only after the column 404 has aged and the baseline has stabilized.

[0068] Figure 12 In the figure, Us is the interference signal source, and the interference current Is generates interference currents I1 and I2 on the two conductors L1 and L2 of the two-wire circuit respectively. Since L1 is closer to the interference source, I1 is much larger than I2, I=I1-I2≠0, and interference current exists. The interference signal interferes with the twisted two-wire circuit, see Figure 2 .and Figure 1 The difference is that the two-wire loop is twisted at the midpoint. Interference currents I11 and I12 are present on L1, and I21 and I22 are present on L2. Interference current I = I21 + I22 - I11 - I12. Since the conditions on both lines are identical, the total interference current I = 0. Therefore, by setting a reasonable lay length, interference can be eliminated. US is the signal voltage, and RS is the load impedance.

[0069] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for real-time detection of contamination of a chromatographic column by a high-concentration sample, characterized in that: The steps include: (1) Signal acquisition: The concentration value of the sample gas is reflected in the micro-voltage signal in the output signal of the gas chromatograph detector (403). The micro-voltage signal in the gas chromatograph signal output by the detector (403) is intercepted, and a signal for feedback of the sample concentration is intercepted from the gas chromatograph output signal to obtain micro-voltage information A; Using a shielded twisted pair cable to intercept the micro-voltage signal; (2) Signal conditioning: The micro-voltage information A is amplified in multiple stages after passing through an integrated operational amplifier to form micro-voltage information B, and the micro-voltage information B is amplified through a filter amplifier to form micro-voltage information C; (3) Signal conversion: The micro-voltage information C is converted into a digital signal D via an AD converter, converting the analog signal into a digital signal; (4) Signal filtering and calculation: The signal filtering adopts the pulse interference-proof average filtering algorithm. The digital signal D is connected to the data display device on the digital circuit. The signal filtering adopts the pulse interference-proof average filtering algorithm. The pulse interference-proof average algorithm first compares N sampling signals, finds the maximum and minimum values, eliminates them, and then performs average calculation to calculate the sample concentration value E, E = (A0 + A1 + ... A20) - AMAX - AMIN) / 19; where A0-A20 represents the sampling value; AMAX represents the maximum sampling value; AMIN represents the minimum sampling value; 19 represents the number of sampling values; (5) Monitoring the sample concentration value: Based on the stability of the monitoring baseline, when the sample concentration value is greater than or equal to the alarm concentration value, the automatic sampler stops and alarms, and automatically or manually intervenes to increase the temperature of the gas chromatography column (404) oven, and then increases the temperature by 20°C again to age the chromatographic column (404), and purges the injection pipeline until the sample concentration value returns to normal and the baseline returns to stability; The standard for the sample concentration value to return to normal is that the electrical signal gradually approaches the original zero value, that is, the fluctuation is less than plus or minus 20 microvolts.

2. A device for real-time detection of contamination of a chromatographic column by a high-concentration sample using the method of claim 1, characterized in that: It includes an information monitoring and transmission mechanism (3), a control mechanism (1), a chromatographic gas path mechanism (4), and an injector gas path mechanism (2) connected to the inlet of the chromatographic gas path mechanism (4); The chromatographic gas path mechanism (4) includes a chromatographic column (404), a temperature control box (5) for accommodating the chromatographic column (404), and a detector (403) connected to the chromatographic column (404); The information monitoring and transmission mechanism (3) includes a signal amplifying board (303), a signal converter (302), and a chromatography workstation (301) in sequence along the direction of electrical information transmission. The input end of the signal amplifying board (303) is connected to the detector (403), and the output end of the signal amplifying board (303) is also connected to the signal acquisition board (103) of the control mechanism (1). The control mechanism (1) includes a main control board (102), an input end of the main control board (102) is connected to the signal acquisition board (103), and an output end of the main control board (102) is connected to the injector host computer (101) and the opening and closing switches corresponding to the components in the injector gas path mechanism (2); An electric heating device (6) is provided in the temperature control box (5), and the circuit of the electric heating device (6) is connected to the output end of the main control board (102); The injector gas path mechanism (2) includes a sampling circuit and a purge circuit that are selectively opened and connected via an injection valve (209) and a two-position three-way solenoid valve (206), wherein the sampling circuit includes a container loaded with sampling gas and connected to the injection valve (209), and a vacuum pump (201), wherein the purge circuit includes an inert gas container and a pressure regulating valve (211) and a flow regulating valve (210) connected thereto.

3. The device for real-time detection of contamination of a chromatographic column by a high-concentration sample according to claim 2, characterized in that: The sampling circuit includes at least two sampling gas containers, and the outlet of each sampling gas container is connected in parallel to the inlet of the selection valve (207) as a branch pipeline, and the outlet of the selection valve (207) is connected to the injection valve (209).

4. The device for real-time detection of contamination of a chromatographic column by a high-concentration sample according to claim 2, characterized in that: The detector (403) and the signal amplifying board (303) are connected via two shielded twisted wires.

5. The device for real-time detection of contamination of a chromatographic column by a high-concentration sample according to claim 2, characterized in that: An air resistance (205) is provided between the air inlet of the vacuum pump (201) and the two-position three-way valve.

6. The device for real-time detection of contamination of a chromatographic column by a high-concentration sample according to claim 2, characterized in that: The signal amplifying board (303) is provided with an LC filter circuit a, an input signal amplifying circuit b, a signal conditioning circuit c, a primary filter circuit d, and a secondary filter circuit e in sequence, wherein the input signal amplifying circuit b and the signal conditioning circuit c are each connected in parallel with an independent branch filter circuit f.

Images