Switching valve device of multi-mode online ion chromatograph and analysis method

Abstract

The switching valve device comprises a first switching valve, a second switching valve, a third switching valve, a fourth switching valve, a fifth switching valve and an enrichment column, the first switching valve is connected with a real-time water sample inlet, the second switching valve is connected with an automatic sample injector and a filter, and the second switching valve is connected with the enrichment column. The third switching valve is connected with the leacheate generator, the sample injector valve and the enrichment column, the fourth switching valve is connected with the conductance cell and the enrichment column, the fifth switching valve is connected with the enrichment column and the chromatographic column, and high integration of three analysis modes of real-time online detection, automatic sample injector sample injection and two-dimensional sample injection is realized through the specific connection relation between the first to fifth switching valves and the enrichment column.

Description

Technical Field

[0001] This application relates to the field of water quality testing technology, specifically to the field of switching valve devices and analytical methods for multi-mode online ion chromatographs. Background Technology

[0003] Traditional manual laboratory testing methods are cumbersome, time-consuming, and labor-intensive, making them unsuitable for long-term, continuous, and real-time monitoring of critical water sources and treated water. Especially when responding to sudden water pollution incidents or seasonal risks such as saltwater intrusion, conventional testing methods exhibit significant data lag, failing to provide timely and effective technical support for emergency decision-making.

[0004] In response, ion chromatography, as an authoritative method for detecting anions and cations in water, has been widely used in the field of water quality analysis. However, existing online ion chromatography equipment generally suffers from limitations in functionality: some devices only support online detection at a fixed frequency, lacking flexibility; while some devices have automatic sample introduction capabilities, they cannot achieve truly unmanned long-term operation; more importantly, when dealing with water samples with complex compositions (such as coastal waters affected by salinity intrusion), high concentrations of coexisting ions (such as chlorides and sulfates) can severely interfere with adjacent disinfection byproducts (such as dichloroacetic acid and trichloroacetic acid), leading to distorted detection results and seriously affecting the accuracy and reliability of online detection data.

[0005] In summary, current technologies lack a comprehensive online ion chromatography solution that can accommodate multiple application scenarios, achieve full-time coverage, and effectively overcome matrix interference. Summary of the Invention

[0006] This application proposes a switching valve device and analysis method for a multi-mode online ion chromatograph to solve the problems of existing technologies, such as inability to accommodate multiple detection scenarios, inability to achieve unattended operation, and high-concentration ion interference.

[0007] To achieve the above objectives, the present application adopts the following technical solution: In a first aspect, this application proposes a switching valve device for a multi-mode online ion chromatograph, comprising: a first switching valve, a second switching valve, a third switching valve, a fourth switching valve, a fifth switching valve, and an enrichment column; The fourth port of the first switching valve is the real-time water sample inlet, the third port is connected to the sixth port of the second switching valve, and the fifth port is the online water sample discharge port. The second port of the second switching valve is connected to the outlet of the autosampler, and the first port is connected to the inlet of the filter; The first port of the third switching valve is connected to the outlet of the eluent generator, the second port is connected to the sample inlet of the injector valve, and the third port is connected to the inlet of the enrichment column. The outlet of the filter is connected to the sample inlet of the injector valve; the first port of the fourth switching valve is connected to the outlet of the conductivity cell, and the third port is connected to the inlet of the enrichment column. The first port of the fifth switching valve is connected to the outlet of the enrichment column, and the third port is connected to the inlet of the chromatographic column.

[0008] Thus, the switching valve device of the multi-mode online ion chromatograph provided in this application achieves a high degree of integration of three analytical modes: real-time online detection, autosampler injection, and two-dimensional injection, through the specific connection relationship between the first to fifth switching valves and the enrichment column. Firstly, its compact structure and simple piping enhance the overall system integrity and reliability; moreover, it enables rapid and non-destructive automatic switching between multiple modes, significantly improving analytical efficiency and automation levels.

[0009] In some possible implementations, the first switching valve, the second switching valve, the third switching valve, the fourth switching valve, and the fifth switching valve are all six-way switching valves.

[0010] In some possible implementations, the first switching valve, the second switching valve, the fourth switching valve, and the fifth switching valve all have ports connected to waste liquid pipes.

[0011] In some possible implementations, the third port of the third switching valve is connected to the inlet of the enrichment column.

[0012] In some possible implementations, the third port of the fourth switching valve is connected to the inlet of the enrichment column via a tee connector, and the third port of the third switching valve is also connected to the tee connector.

[0013] In some possible implementations, the enrichment column is filled with an adsorbent material for enriching anions.

[0014] Secondly, this application also proposes an analytical method using a multi-mode online ion chromatograph switching valve device, comprising the following steps: S1: Select the autosampler injection mode, real-time online detection mode, or two-dimensional injection mode according to the source of the sample to be tested and the analysis requirements; S2: The control system generates control commands based on the selected mode and sends them to the first to fifth switching valves; S3: Each switching valve responds to the control command, adjusts its port on / off state, and constructs the corresponding sample flow path; S4: The sample is injected, separated, and detected in the constructed flow path to obtain analytical results.

[0015] Thus, by systematically integrating analysis mode selection, control command generation, automatic flow path construction, and sample analysis workflow, intelligent and one-click switching between different injection modes is achieved. This method eliminates the need for manual intervention or reconnection of tubing, allowing flexible selection of autosampler injection, real-time online detection, or two-dimensional injection modes based on actual needs. This significantly shortens mode switching time, avoids the risks of misconnection, leakage, or contamination caused by manual operation, and improves the automation level, ease of operation, and reliability of results in the analysis process. Simultaneously, this method fully leverages the hardware advantages of the switching valve device, providing a reliable technical path for continuous, efficient, and high-sensitivity detection of samples in complex aquatic environments.

[0016] In some possible implementations, when the autosampler injection mode is selected, step S3 specifically includes: The second switching valve is controlled to open the flow path between the autosampler outlet and the filter, while the first switching valve is controlled to close the real-time water sample inlet flow path. The filter outlet is connected to the quantitative loop of the injector valve, and the third switching valve is controlled to be in the injection preparation state, so that the eluent generator is connected to the drive flow path of the injector valve to maintain system balance. Control the fourth switching valve to open the flow path from the conductivity cell outlet to the waste liquid pipe and close the flow path of the enrichment column; When the autosampler completes sample extraction and sends an injection signal, the autosampler valve is switched to the injection position, causing the eluent to push the sample in the quantitative loop into the chromatographic column for separation and analysis.

[0017] In some possible implementations, when the real-time online detection mode is selected, step S3 specifically includes: The first switching valve is controlled to open the flow path between the real-time water sample inlet and the filter, while the second switching valve is controlled to close the flow path of the autosampler. The filter outlet is connected to the quantitative loop of the injector valve, and the third switching valve is controlled to be in the injection preparation state, so that the eluent generator is connected to the drive flow path of the injector valve to maintain system balance. Control the fourth switching valve to open the flow path from the conductivity cell outlet to the waste liquid pipe and close the flow path of the enrichment column; When the preset injection cycle is reached, the injector valve is switched to the injection position, so that the eluent pushes the sample in the quantitative loop into the chromatographic column for separation and analysis.

[0018] In some possible implementations, when the two-dimensional injection mode is selected, step S3 specifically includes: Step S31: Complete the first separation analysis of step S3 as described above in autosampler injection mode or real-time online detection mode; Step S32: Control the fourth switching valve to open the flow path between the outlet of the conductivity cell and the inlet of the enrichment column, so that the effluent from the first injection enters the enrichment column and the target substance is adsorbed and enriched. At the same time, the fifth switching valve remains closed. S33: After the predetermined enrichment time is over, control the third switching valve to switch to its third port, and introduce the eluent generated by the eluent generator into the enrichment column to elute the target analyte. S34: Controls the fifth switching valve to open the flow path between the enrichment column outlet and the chromatographic column inlet, so that the eluted target analyte enters the chromatographic system under the push of the eluent for a second separation and analysis. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the switching valve device in the autosampler injection mode in this application; Figure 2 This is a chromatogram of experimental data results in autosampler injection mode in this application; Figure 3 This is a schematic diagram of the status of the switching valve device in real-time online detection mode in this application; Figure 4 This is a schematic diagram of the switching valve device in the two-dimensional injection mode in this application; Figure 5 In two-dimensional injection mode, the experiment extracts peak fragments of dichloroacetic acid and trichloroacetic acid from the first injection for secondary injection analysis of the spectrum; Figure 6 This is a peak spectrum of dichloroacetic acid and trichloroacetic acid obtained from a single injection. Figure 7 This is the peak spectrum of dichloroacetic acid and trichloroacetic acid after two injections. Detailed Implementation

[0020] The following examples further illustrate the features of this application and other related features in detail, so as to facilitate understanding by those skilled in the art: It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions in the attached diagrams, while the terms “bottom surface,” “top surface,” “inner,” and “outer” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0021] Furthermore, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this case based on the specific circumstances.

[0022] The switching valve device for the multi-mode online ion chromatograph provided in this application embodiment, such as... Figure 1 , Figure 3 and Figure 4 As shown, the system includes a first switching valve, a second switching valve, a third switching valve, a fourth switching valve, a fifth switching valve, and an enrichment column. The fourth port of the first switching valve is the real-time water sample inlet, the third port is connected to the sixth port of the second switching valve, and the fifth port is the online water sample waste discharge port. The second port of the second switching valve is connected to the outlet of the autosampler, and the first port is connected to the inlet of the filter. The first port of the third switching valve is connected to the outlet of the eluent generator, the second port is connected to the sample inlet of the autosampler valve, and the third port is connected to the inlet of the enrichment column. The outlet of the filter is connected to the sample inlet of the autosampler valve. The first port of the fourth switching valve is connected to the outlet of the conductivity cell, and the third port is connected to the inlet of the enrichment column. The first port of the fifth switching valve is connected to the outlet of the enrichment column, and the third port is connected to the inlet of the chromatographic column. This port configuration achieves physical isolation between the sample injection and waste discharge paths and independent purging and flushing of the pipelines, balancing injection accuracy, system stability, and ease of maintenance.

[0023] In this embodiment, the first switching valve, the second switching valve, the third switching valve, the fourth switching valve, and the fifth switching valve are all six-way switching valves, and each of the first switching valve, the second switching valve, the fourth switching valve, and the fifth switching valve has one port connected to a waste liquid pipe for draining the flow path when not in operation, to prevent residue and cross-contamination.

[0024] In some embodiments, the third port of the third switching valve is connected to the inlet of the enrichment column to support eluent elution in two-dimensional injection mode. Preferably, the second port of the fourth switching valve is connected to the inlet of the enrichment column via a tee connector, and the third port of the third switching valve is also connected to this tee connector, allowing the eluent to mix with the effluent from the first injection before entering the enrichment column. The enrichment column is filled with an adsorbent material for enriching anions, which can selectively adsorb target substances such as dichloroacetic acid and trichloroacetic acid.

[0025] Thus, the switching valve device of the multi-mode online ion chromatograph provided in this application achieves a high degree of integration of three analytical modes: real-time online detection, autosampler injection, and two-dimensional injection, through the specific connection relationship between the first to fifth switching valves and the enrichment column. Firstly, its compact structure and simple piping enhance the overall system integrity and reliability; moreover, it enables rapid and non-destructive automatic switching between multiple modes, significantly improving analytical efficiency and automation levels.

[0026] Especially in two-dimensional injection mode, the third switching valve directly introduces eluent to the enrichment column for elution, successfully achieving online enrichment and secondary separation of trace targets, significantly improving detection sensitivity and selectivity. Meanwhile, each switching valve is equipped with a waste liquid discharge path, facilitating system maintenance and reducing operating costs.

[0027] This application also provides an analytical method using the aforementioned multi-mode online ion chromatograph switching valve device. This method, through a control system, executes steps S1 to S4 based on the source of the sample and analytical requirements to achieve intelligent switching between different analytical modes. Specifically, S1: Select the autosampler injection mode, real-time online detection mode, or two-dimensional injection mode according to the source of the sample to be tested and the analysis requirements; S2: The control system generates control commands based on the selected mode and sends them to the first to fifth switching valves; S3: Each switching valve responds to the control command, adjusts its port on / off state, and constructs the corresponding sample flow path; S4: The sample is injected, separated, and detected in the constructed flow path to obtain analytical results.

[0028] When executing the autosampler injection mode, such as Figure 1 As shown, the control system controls the second switching valve to open its first and second ports, allowing the sample extracted by the autosampler to enter the quantitative loop of the injector valve through the filter. Simultaneously, the first switching valve closes to isolate the real-time water sample inlet. The third switching valve is configured in the injection preparation state, ensuring that the eluent output from the eluent generator continuously flows through the drive path of the injector valve, maintaining system flow balance. The fourth switching valve opens the flow path from the conductivity cell outlet to the waste liquid pipe and closes the enrichment column flow path.

[0029] When the autosampler completes sample extraction and sends an injection signal, the control system triggers the autosampler valve to switch to the injection position. The eluent then pushes the sample in the quantitative loop into the chromatographic column, where it passes through the suppressor and conductivity cell for separation and detection.

[0030] In practical applications, this mode is suitable for automated analysis of batch samples. A series of mixed standard solutions are prepared by mixing standard solutions of anionic fluorides, chlorites, bromates, chlorides, dichloroacetic acid, chlorates, bromides, nitrates, trichloroacetic acid, and sulfates in a specific ratio. The samples are then injected into an online ion chromatograph using the autosampler injection mode. The results show that the ten substances can be completely separated, and the detection is completed within 36 minutes. Experimental data are as follows: Figure 2 As shown, the system exhibits good stability and repeatability. The numerical symbols in the figure are: 2 fluoride, 3 chlorite, 4 bromate, 5 chloride, 6 dichloroacetic acid, 7 chlorate, 8 bromide, 9 nitrate, 10 trichloroacetic acid, and 11 sulfate.

[0031] The linear equations, correlation coefficients, and precision results for each substance were good, with correlation coefficients ranging from 0.9993 to 0.99999. In six injection tests, the relative standard deviations of the mass concentrations ranged from 0.55% to 2.07%, indicating stable instrument performance (see Table 1 for details).

[0032]

[0033] Table 1 When executing real-time online detection mode, such as Figure 3 As shown, the control system controls the first switching valve to open the flow path between the real-time water sample inlet and the filter, allowing the water sample to continuously enter the system. Simultaneously, the second switching valve closes to block the autosampler flow path. The third switching valve is in the sample preparation state, ensuring a continuous supply of eluent to the autosampler valve. The fourth switching valve opens the flow path from the conductivity cell outlet to the waste liquid pipe and closes the enrichment column flow path.

[0034] The system performs timed injections according to a preset injection cycle: when the cycle is reached, the injector valve switches to the injection position, injecting the sample accumulated in the quantitative loop into the chromatographic system for analysis. This mode enables long-term, continuous, and unattended monitoring of key nodes such as source water and treated water, effectively solving the data lag problem of traditional detection methods.

[0035] In practical application, the experiment was conducted during the off-duty hours from 10 PM to 6 AM the following day, with real-time monitoring of the water leaving the water plant. Monitoring was performed once per hour on average, and the real-time monitoring results are shown in Table 2 below. The experimental results show that the water quality leaving the plant was consistently qualified during the unattended period of the laboratory.

[0036]

[0037] Table 2 Real-time detection data results When executing the two-dimensional injection mode, such as Figure 4 As shown, the system first completes step S31, which involves performing the first separation analysis in either autosampler injection mode or real-time online detection mode. Then, the control system executes step S32, controlling the fourth switching valve to open the flow path between the conductivity cell outlet and the enrichment column inlet, allowing the effluent from the first injection to enter the enrichment column, where the target analyte is adsorbed and enriched. Simultaneously, the fifth switching valve remains closed. After the predetermined enrichment time, step S33 is executed, where the control system switches the third switching valve to its third port, introducing the eluent generated by the eluent generator into the enrichment column for elution of the target analyte. Finally, step S34 is executed, controlling the fifth switching valve to open the flow path between the enrichment column outlet and the chromatographic column inlet, allowing the eluted target analyte to enter the chromatographic system under the influence of the eluent for a second separation analysis.

[0038] In coastal areas, the water is highly susceptible to saltwater intrusion, resulting in higher chloride content compared to inland cities. The peak elution time of chloride is similar to that of dichloroacetic acid, and high chloride concentrations can easily affect the peak elution of dichloroacetic acid. Carbonate and high concentrations of sulfate can also affect the peak elution of trichloroacetic acid.

[0039] like Figure 5 As shown, this mode successfully captured the peak fragments of dichloroacetic acid and trichloroacetic acid that were interfered with by high concentrations of coexisting ions in the first injection, and achieved clear and interference-free separation in the second analysis. Figure 6 and Figure 7 The peak elution of dichloroacetic acid and trichloroacetic acid in the first and second injections are shown, which fully verifies the excellent performance of this method in detecting trace disinfection byproducts in complex matrices.

[0040] A series of mixed standard solutions of dichloroacetic acid and trichloroacetic acid were prepared by mixing standard solutions of dichloroacetic acid and trichloroacetic acid in a certain proportion. The solutions were then introduced into an online ion chromatograph using two-dimensional injection mode. The results showed that dichloroacetic acid and trichloroacetic acid had good linearity and the instrument performance was stable. The results are shown in Table 3.

[0041]

[0042] Table 3 Two-dimensional data results Thus, by systematically integrating analysis mode selection, control command generation, automatic flow path construction, and sample analysis workflow, intelligent and one-click switching between different injection modes is achieved. This method eliminates the need for manual intervention or reconnection of tubing, allowing flexible selection of autosampler injection, real-time online detection, or two-dimensional injection modes based on actual needs. This significantly shortens mode switching time, avoids the risks of misconnection, leakage, or contamination caused by manual operation, and improves the automation level, ease of operation, and reliability of results in the analysis process. Simultaneously, this method fully leverages the hardware advantages of the switching valve device, providing a reliable technical path for continuous, efficient, and high-sensitivity detection of samples in complex aquatic environments.

[0043] As stated above, this case protects the switching valve device and analytical method of a multi-mode online ion chromatograph, and all technical solutions that are the same as or similar to this case should be considered to fall within the protection scope of this case.

Claims

1. A switching valve device for a multi-mode online ion chromatograph, characterized in that, include: First switching valve, second switching valve, third switching valve, fourth switching valve, fifth switching valve and enrichment column; The fourth port of the first switching valve is the real-time water sample inlet, the third port is connected to the sixth port of the second switching valve, and the fifth port is the online water sample discharge port. The second port of the second switching valve is connected to the outlet of the autosampler, and the first port is connected to the inlet of the filter; The first port of the third switching valve is connected to the outlet of the eluent generator, the second port is connected to the sample inlet of the injector valve, and the third port is connected to the inlet of the enrichment column. The outlet of the filter is connected to the sample inlet of the injector valve; the first port of the fourth switching valve is connected to the outlet of the conductivity cell, and the third port is connected to the inlet of the enrichment column. The first port of the fifth switching valve is connected to the outlet of the enrichment column, and the third port is connected to the inlet of the chromatographic column.

2. The switching valve device for the multi-mode online ion chromatograph as described in claim 1, characterized in that, The first switching valve, the second switching valve, the third switching valve, the fourth switching valve, and the fifth switching valve are all six-way switching valves.

3. The switching valve device for the multi-mode online ion chromatograph as described in claim 1, characterized in that, The first switching valve, the second switching valve, the fourth switching valve, and the fifth switching valve all have ports connected to the waste liquid pipe.

4. The switching valve device for a multi-mode online ion chromatograph as described in claim 1, characterized in that, The third port of the fourth switching valve is connected to the inlet of the enrichment column via a tee connector, and the third port of the third switching valve is also connected to the tee connector.

5. The switching valve device for a multi-mode online ion chromatograph as described in claim 1, characterized in that, The enrichment column is filled with an adsorbent material for enriching anions.

6. An analytical method using a switching valve device in a multi-mode online ion chromatograph, characterized in that, Includes the following steps: S1: Select the autosampler injection mode, real-time online detection mode, or two-dimensional injection mode according to the source of the sample to be tested and the analysis requirements; S2: The control system generates control commands based on the selected mode and sends them to the first to fifth switching valves; S3: Each switching valve responds to the control command, adjusts its port on / off state, and constructs the corresponding sample flow path; S4: The sample is injected, separated, and detected in the constructed flow path to obtain analytical results.

7. The analytical method using a multi-mode online ion chromatograph switching valve device as described in claim 6, characterized in that, When selecting the autosampler injection mode, step S3 specifically includes: The second switching valve is controlled to open the flow path between the autosampler outlet and the filter, while the first switching valve is controlled to close the real-time water sample inlet flow path. The filter outlet is connected to the quantitative loop of the injector valve, and the third switching valve is controlled to be in the injection preparation state, so that the eluent generator is connected to the drive flow path of the injector valve to maintain system balance. Control the fourth switching valve to open the flow path from the conductivity cell outlet to the waste liquid pipe and close the flow path of the enrichment column; When the autosampler completes sample extraction and sends an injection signal, the autosampler valve is switched to the injection position, causing the eluent to push the sample in the quantitative loop into the chromatographic column for separation and analysis.

8. The analytical method using a multi-mode online ion chromatograph switching valve device as described in claim 6, characterized in that, When the real-time online detection mode is selected, step S3 specifically includes: The first switching valve is controlled to open the flow path between the real-time water sample inlet and the filter, while the second switching valve is controlled to close the flow path of the autosampler. The filter outlet is connected to the quantitative loop of the injector valve, and the third switching valve is controlled to be in the injection preparation state, so that the eluent generator is connected to the drive flow path of the injector valve to maintain system balance. Control the fourth switching valve to open the flow path from the conductivity cell outlet to the waste liquid pipe and close the flow path of the enrichment column; When the preset injection cycle is reached, the injector valve is switched to the injection position, so that the eluent pushes the sample in the quantitative loop into the chromatographic column for separation and analysis.

9. The analytical method using a multi-mode online ion chromatograph switching valve device as described in claim 7 or claim 8, characterized in that, When the two-dimensional injection mode is selected, step S3 specifically includes: Step S31: Complete the first separation analysis of step S3 as described above in autosampler injection mode or real-time online detection mode; Step S32: Control the fourth switching valve to open the flow path between the outlet of the conductivity cell and the inlet of the enrichment column, so that the effluent from the first injection enters the enrichment column and the target substance is adsorbed and enriched. At the same time, the fifth switching valve remains closed. S33: After the predetermined enrichment time is over, control the third switching valve to switch to its third port, and introduce the eluent generated by the eluent generator into the enrichment column to elute the target analyte. S34: Controls the fifth switching valve to open the flow path between the enrichment column outlet and the chromatographic column inlet, so that the eluted target analyte enters the chromatographic system under the push of the eluent for a second separation and analysis.

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