Ion chromatography system

Abstract

An ion chromatography system includes a liquid feed pump that delivers an eluent, a sample injection section fluidly connected downstream of the liquid feed pump to inject a sample into the eluent, a separation column fluidly connected downstream of the sample injection section to separate ion components in the sample from each other, a suppressor fluidly connected downstream of the separation column to apply a suppressor voltage to a flow path through which the eluent from the separation column flows and to remove a prescribed ion component from the eluent, a detector fluidly connected to an outlet of the suppressor to measure electrical conductivity of the eluent from the suppressor, and a system monitoring section that monitors a background value of a measurement value of the detector and the suppressor voltage as monitoring values, respectively, and determines whether a variation occurs in the monitoring values at a prescribed timing, detects when the variation is determined to occur, and determines whether the variation is short-term or long-term occurrence based on a variation rate within a certain time of a prescribed state of the monitoring values most recently, so that a cause of a system abnormality can be easily determined.

Description

Technical Field

[0001] This invention relates to an ion chromatography analysis system. Background Technology

[0002] In ion chromatography, the analyte sample and eluent are introduced into a separation column, where the ionic components in the sample are separated. A detector downstream of the separation column measures the conductivity of the eluent, generating a chromatogram. If the eluent contains unwanted ions, the background of the eluent's conductivity measured by the detector increases, leading to decreased detection sensitivity. Therefore, a suppressor is often placed between the separation column and the detector. This suppressor removes unwanted ions from the eluent and replaces them with hydrogen ions (see Patent Document 1). By replacing unwanted ions with hydrogen ions through the suppressor, the conductivity of the eluent introduced into the detector decreases, reducing the background of the detector signal and enabling highly sensitive ion analysis.

[0003] [Existing technical documents]

[0004] [Patent Literature]

[0005] [Patent Document 1] International Publication No. 2020 / 194609 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] In ion chromatography analysis, background value fluctuations in the measured data sometimes occur. When this anomaly occurs, there is a possibility that ion exchange cannot proceed normally within the suppressor, making analysis impossible. These anomalies, such as background value fluctuations, are believed to be caused by factors such as shortened suppressor lifespan due to years of degradation, internal contamination of the suppressor, incorrect eluent delivery, or poor liquid flow to the suppressor (applying voltage when the suppressor is not flowing). However, when this anomaly occurs, it is difficult for the user to determine the cause. Therefore, it is necessary to temporarily verify various parameters, check piping, and clean the suppressor.

[0008] The present invention was made in view of the aforementioned problems, and its purpose is to detect whether there are any abnormalities in an ion chromatography analysis system, and to easily determine the cause when abnormalities are present.

[0009] [Technical means to solve the problem]

[0010] The ion chromatography analysis system of the present invention includes: a delivery pump for delivering eluent; a sample injection unit configured to be fluidly connected downstream of the delivery pump for injecting a sample into the eluent delivered by the delivery pump; a separation column fluidly connected downstream of the sample injection unit for separating ionic components in the sample injected into the eluent through the sample injection unit; a suppressor configured to be fluidly connected downstream of the separation column for applying a suppressor voltage to the flow path through which the eluent exits from the separation column and removing specified ionic components from the eluent; and a detector fluidly connected to the outlet of the suppressor for detecting... The conductivity of the eluent flowing from the suppressor is measured; and the system monitoring unit is configured to monitor the background value of the detector measurement and the suppressor voltage as monitoring values, and at a predetermined time under a predetermined state in which the eluent is delivered by the delivery pump, determine whether the monitoring value has changed from the previous predetermined state, detect the anomaly when the change is determined to have occurred, and determine whether the change is a short-term change or a long-term change based on the recent rate of change of the monitoring value, and determine the cause of the anomaly by whether the change is a short-term change or a long-term change.

[0011] [The effects of the invention]

[0012] In the ion chromatography analysis system of the present invention, a system monitoring unit is included. The system monitoring unit monitors the background value of the detector measurement and the suppressor voltage as monitoring values. At a predetermined time under a predetermined state, the system not only detects anomalies by checking whether the monitoring values ​​have changed from the previous predetermined state, but also automatically distinguishes the cause of the anomaly by whether the change in the monitoring values ​​is a short-term change or a long-term change. Therefore, when an anomaly exists in the system, its cause can be easily determined. Attached Figure Description

[0013] Figure 1 This is a schematic structural diagram illustrating one embodiment of an ion chromatography analysis system.

[0014] Figure 2 This is a flowchart illustrating an example of system monitoring actions in the described embodiment.

[0015] [Explanation of Symbols]

[0016] 1: Ion Chromatography Analysis System

[0017] 2: Liquid delivery pump

[0018] 4: Automatic Sampler

[0019] 6: Separation column

[0020] 8: Suppressor

[0021] 10: Detector

[0022] 12: Operation and control device

[0023] 14: Monitor

[0024] 16: Voltage application section

[0025] 18: System Monitoring Department Detailed Implementation

[0026] Hereinafter, an embodiment of the ion chromatography analysis system of the present invention will be described with reference to the accompanying drawings.

[0027] The ion chromatography analysis system 1 includes a liquid delivery pump 2, an autosampler 4, a separation column 6, a suppressor 8, a detector 10, a computing control device 12, and a display 14.

[0028] Pump 2 is used to deliver the eluent.

[0029] The autosampler 4 is fluidly connected downstream of the delivery pump 2 and injects the sample into the eluent delivered by the delivery pump 2.

[0030] The suppressor 8 is fluidly connected downstream of the separation column 6 and removes specified ionic components from the eluent to reduce its electrical conductivity. A voltage application section 16 is provided in the suppressor 8, which applies a suppressor voltage to the flow path through which the eluent flowing from the outlet of the separation column 6 passes. The voltage application section 16 performs constant current control of the suppressor voltage to maintain a constant electrical conductivity of the eluent flowing within the flow path.

[0031] The detector 10 is fluidly connected downstream of the suppressor 8 and is used to measure the electrical conductivity of the eluent passing through the suppressor 8.

[0032] The computational control device 12 is used to manage the operation of the ion chromatography analysis system 1, and is implemented by a computer device such as a personal computer including a central processing unit (CPU) and a data storage device. The display 14 is communicatively connected to the computational control device 12.

[0033] The operational control device 12 includes a system monitoring unit 18. The system monitoring unit 18 functions through software stored in the operational control device 12. The system monitoring unit 18 monitors the suppressor voltage of the suppressor 8 and the background value (hereinafter, BG (Base Ground) value) of the conductivity measured by the detector 10 as monitoring values, and records each monitoring value in the data storage memory of the operational control device 12 in a frequency distribution format. Furthermore, the system monitoring unit 18 determines whether an anomaly has occurred in the system 1 by checking whether the monitoring values ​​under a specified state have changed from the normal state, and if an anomaly has occurred, determines the cause of the anomaly based on the magnitude and / or rate of change of the monitoring values.

[0034] use Figure 1 as well as Figure 2 The flowchart illustrates an example of a system monitoring operation performed by the system monitoring unit 18.

[0035] The system monitoring unit 18 performs the system monitoring actions described below at a predetermined time when the system state is in a predetermined state. The following describes an example of performing system monitoring actions when the analytical method is updated. A predetermined state refers to a state where a predetermined eluent is stably supplied at a predetermined flow rate, and where no sample is injected into the eluent. An analytical method is a set of analytical conditions, including the type of eluent used, the flow rate of the eluent, and the temperature of the separation column 6 (column oven). Since the analytical method is set for each analysis, in continuous analysis where multiple analyses are performed consecutively, the analytical method to be used in the next analysis is updated after each analysis. Therefore, the system monitoring unit 18 performs the system monitoring actions described below each time an analysis is completed and the method set for the next analysis is read.

[0036] The system monitoring unit 18 updates the analysis method and reads the BG value and suppressor voltage when the system is in standby mode (step 101). The BG value and suppressor voltage to be read are not instantaneous values ​​but average values ​​over a certain period (e.g., 5 seconds). The system monitoring unit 18 determines whether the BG value has changed from its normal value (step 102). If the BG value has not changed from its normal value, the system 1 is determined to be normal (i.e., without abnormalities) (step 103).

[0037] The normal value of the BG value can be, for example, the average value of the BG values ​​obtained when the system was in a specified state (the same type of eluent as the one set by the current analysis method was used and transported at the same flow rate). The system monitoring unit 18 uses the normal BG value and sets a reference range, such as the normal BG value ± α, as the basis for determining whether the BG value has changed from the normal state. If the read BG value is within the reference range, it is determined that the BG value has not changed from the normal state (step 102: No). If the read BG value deviates from the reference range, it is determined that the BG value has changed from the normal state (step 102: Yes).

[0038] When the system monitoring unit 18 determines that the BG value has changed from its normal value, it detects anomalies within the system and determines whether the change is short-term or long-term (step 104). A short-term change in the BG value refers to a rapid change in the BG value within a short period of time, while a long-term change in the BG value refers to a gradual change in the BG value within a long period of time. Whether a change in the BG value is short-term or long-term can be determined based on the rate of change (change amount / time) of the BG value within the most recent certain period of time (e.g., 300 seconds) when the system state is in a specified state. When the system monitoring unit 18 determines that the BG value has changed from its normal value, it calculates the rate of change of the BG value within the most recent certain period of time. If the calculated rate of change deviates from the specified range, it is determined to be a short-term change (step 104: Yes); if the rate of change is within the specified range, it is determined to be a long-term change (step 104: No).

[0039] The causes of short-term fluctuations in the BG value can be attributed to factors such as dry burning of the suppressor 8 or errors in the eluent. Dry burning of the suppressor 8 refers to situations where, due to factors such as piping errors, the eluent does not flow through the suppressor 8 (poor flow to the suppressor 8), and the eluent is introduced to the detector 10 without passing through the suppressor 8; or the eluent is not introduced into the suppressor 8 or the detector 10. In such cases, the eluent flowing within the detector 10 does not pass through the suppressor 8 or is not introduced into the detector 10, therefore the conductivity of the eluent measured by the detector 10 changes significantly before and after the dry burning of the suppressor, resulting in a larger rate of change in the recent BG value. At this time, when the suppressor voltage is applied to the suppressor 8 without any eluent flowing, the suppressor voltage also increases significantly. On the other hand, "errors in the eluent" refers to a situation where the type of eluent delivered by the delivery pump 2 differs from the eluent specified in the analytical method. In this case, the types and / or amounts of ions contained in the currently supplied eluent differ from those set by the current analytical method, thus causing a sharp change in the electrical conductivity of the eluent flowing within detector 10 from its most recent value. In this case, the suppressor voltage of suppressor 8 may also change from its normal value, but the change is smaller than in the case of "suppressor 8 running dry."

[0040] When the system monitoring unit 18 detects short-term fluctuations in the BG value by setting the reference range for determining whether the suppressor voltage fluctuation is large as the average value of the suppressor voltage under normal conditions ± β, it determines whether the suppressor voltage fluctuation from the normal condition is large based on whether the suppressor voltage is within the reference range (step 105). Furthermore, if the suppressor voltage fluctuation from the normal condition is large (step 105: Yes), the system monitoring unit 18 determines the cause of the anomaly as "dry burning of suppressor 8" (step 106), and if the suppressor voltage fluctuation from the normal condition is small (step 105: No), the cause of the anomaly is determined as "eluent error" (step 107). Moreover, in the case of suppressor 8 dry burning, the short-term fluctuation rate of the suppressor voltage is significantly larger than in the case of an eluent error; therefore, the magnitude of the most recent fluctuation rate of the suppressor voltage can be used instead of the magnitude of the suppressor voltage fluctuation to distinguish the cause of the anomaly.

[0041] Furthermore, the long-term fluctuations in the BG value can be attributed to factors such as the deterioration of the suppressor 8 and internal contamination of the suppressor 8. When the suppressor 8 deteriorates, its ability to remove unwanted ions from the eluent decreases, and the conductivity of the eluent after passing through the suppressor 8 increases compared to normal. Additionally, when the suppressor 8 deteriorates, a higher suppressor voltage is required to remove unwanted ions from the eluent, thus the suppressor voltage also increases compared to normal. On the other hand, when internal contamination occurs in the suppressor 8, the conductivity of the eluent after passing through the suppressor 8 increases due to ions retained within the suppressor 8, while the suppressor voltage does not change significantly from its normal value compared to cases of suppressor 8 deterioration.

[0042] When the system monitoring unit 18 detects long-term fluctuations in the BG value by setting a reference range for determining whether the suppressor voltage changes significantly from its normal value, it determines whether the suppressor voltage changes significantly from its normal value based on whether the suppressor voltage is within the reference range (step 108). Furthermore, if the suppressor voltage changes significantly from its normal value (step 108: Yes), the system monitoring unit 18 determines the cause of the abnormality as "deterioration of the suppressor 8" (step 109), and if the suppressor voltage changes little from its normal value (step 108: No), the system monitoring unit 18 determines the cause of the abnormality as "contamination of the suppressor 8" (step 110).

[0043] When the system monitoring unit 18 detects system anomalies based on changes in the BG value and determines the cause of the anomaly, it displays the determined cause on the display 14 or similar device and informs the user. This eliminates the need for the user to perform temporary tasks to eliminate the anomaly, thus reducing the user's workload when an anomaly occurs.

[0044] Furthermore, the embodiments described above are merely one example of implementation of the ion chromatography analysis system of the present invention. Implementation of the ion chromatography analysis system of the present invention is as follows.

[0045] In one embodiment of the ion chromatography analysis system of the present invention, the system includes: a delivery pump for delivering eluent; a sample injection unit configured to be fluidly connected downstream of the delivery pump for injecting a sample into the eluent delivered by the delivery pump; a separation column fluidly connected downstream of the sample injection unit for separating ionic components in the sample injected into the eluent through the sample injection unit; a suppressor configured to be fluidly connected downstream of the separation column for applying a suppressor voltage to the flow path through which the eluent flows from the outlet of the separation column and removing a specified ionic component from the eluent; and a detector fluidly connected to the outlet of the suppressor for detecting the ionic components flowing from the eluent. The system measures the electrical conductivity of the eluent flowing out of the suppressor; and the system monitoring unit is configured to monitor the background value of the detector's measurement and the suppressor voltage as monitoring values, and at a predetermined time under a predetermined state in which the eluent is delivered by the delivery pump, determine whether the monitoring value has changed from the previous predetermined state. If the change is determined to have occurred, an anomaly is detected, and the rate of change of the monitoring value over a certain period of time under the most recent predetermined state is used to determine whether the change is a short-term change or a long-term change, and the cause of the anomaly is determined by whether the change is a short-term change or a long-term change.

[0046] In one embodiment [1], the system monitoring unit is configured to: set a first reference range for the background value and a second reference range for the suppressor voltage based on the background value and the suppressor voltage when the ion chromatography analysis system is in normal operation; determine that the background value has changed when the background value deviates from the first reference range; and determine that the suppressor voltage has changed when the suppressor voltage deviates from the second reference range.

[0047] In one embodiment [2],

[0048] The system monitoring unit is,

[0049] The system is configured to detect the anomaly when it is determined that the background value has changed.

[0050] The configuration is such that when the change in the background value is a long-term change, either the degradation of the suppressor or the internal contamination of the suppressor is determined as the cause of the anomaly based on the magnitude or rate of change of the suppressor voltage.

[0051] The configuration is such that when the change in the background value is a short-term change, either poor liquid flow to the suppressor or an error in the eluent is determined as the cause of the anomaly based on the magnitude of the change in the suppressor voltage or the magnitude of the rate of change.

[0052] In one embodiment [3], the system monitoring unit is configured to: determine that the change in the background value is a long-term change when the most recent rate of change of the background value is within a first predetermined range, and determine that the change in the background value is a short-term change when the most recent rate of change of the background value is within a second predetermined range, wherein the first predetermined range is smaller than the second predetermined range.

[0053] In one embodiment [4], the system monitoring unit is configured to notify the user of the determined cause when the anomaly is detected and the cause of the anomaly is determined.

Claims

1. An ion chromatography analysis system, comprising: The eluent pump delivers the eluent. The sample injection section is configured to be fluidly connected downstream of the delivery pump to inject the sample into the eluent delivered by the delivery pump. A separation column, fluidly connected downstream of the sample injection section, is used to separate the ionic components in the sample injected into the eluent through the sample injection section. An inhibitor is configured to be fluidly connected downstream of the separation column, applying an inhibitor voltage to the flow path through which the eluent flows from the outlet of the separation column, and removing specified ionic components from the eluent; A detector, fluidly connected to the outlet of the suppressor, measures the electrical conductivity of the eluent flowing out of the suppressor; as well as The operational control unit monitors the background value of the detector's measured values ​​and the suppressor voltage, and manages the state of the ion chromatography analysis system based on the background value and the suppressor voltage. The computation control device is configured such that, The system stores a first reference range, a second reference range, and a third reference range. The first reference range is set based on the background value when the eluent is stably delivered by the pump at a specified flow rate, the eluent is free of sample, and the ion chromatography analysis system is functioning normally. The second reference range is a reference range for the rate of change of the background value over a certain period of time. The third reference range is set based on the suppressor voltage when the eluent is stably delivered by the pump at the specified flow rate, the eluent is free of sample, and the ion chromatography analysis system is functioning normally. The background value at a predetermined time when the eluent is stably delivered by the delivery pump at the predetermined flow rate and no sample is injected into the eluent is compared with the first reference range. When the background value deviates from the first reference range, the anomaly of the ion chromatography analysis system is detected. When the anomaly is detected, the rate of change of the background value within the most recent certain period of time is calculated when the eluent is stably delivered by the delivery pump at the specified flow rate and no sample is injected into the eluent. The calculated rate of change is compared with the second reference range to determine whether the calculated rate of change is within the second reference range, and further to determine whether the suppressor voltage at the specified time is within the third reference range. When the rate of change of the background value deviates from the second reference range, if the suppressor voltage is within the third reference range, then the error of the eluent is determined to be the cause of the anomaly; if the suppressor voltage deviates from the third reference range, then the poor flow of the suppressor is determined to be the cause of the anomaly. When the rate of change of the background value is within the second reference range, if the suppressor voltage is within the third reference range, then internal contamination of the suppressor is determined to be the cause of the anomaly; if the suppressor voltage deviates from the third reference range, then degradation of the suppressor is determined to be the cause of the anomaly.

2. The ion chromatography analysis system according to claim 1, wherein, The operation control device is configured to notify the user of the determined cause when the anomaly is detected and the cause of the anomaly is determined.

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