Method and system for automatically adjusting a suppressor

Abstract

A system for automatically adjusting an ion chromatography suppressor includes an ion chromatography suppressor; a power supply for applying an electrical potential to the suppressor; and a control unit configured to apply an offset voltage V OS and an applied voltage V A to the suppressor; measure a current of the suppressor in response to the offset voltage V OS and the applied voltage V A ; determine a suppressor state of the suppressor based on the measured current; and adjust the offset voltage V OS based on the suppressor state. A method for automatically adjusting an ion chromatography suppressor is also disclosed.

Description

Technical Field

[0001] This application generally relates to the separation of ionic substances in ion chromatography, and more specifically, to methods and systems for automatically adjusting suppressors during ion chromatography. Background Technology

[0002] Ion chromatography is widely used to analyze samples containing anions or cations. Suppressors play a crucial role in ion chromatography by making analytes detectable.

[0003] A typical ion chromatography procedure begins by introducing the sample into a conductive eluent solution. The sample ions in the eluent are then chromatographically separated. The eluent is then suppressed to remove eluent ions with opposite conductivity to the sample ions, and finally, the sample ions are detected. The purpose of suppression is to reduce the background conductivity of the eluent and increase the conductivity of the analyte, thereby facilitating subsequent conductive detection of the analyte.

[0004] Suppressors are used to suppress the eluent. A suppressor typically comprises an eluent channel and a regenerator channel, separated by an ion-exchange membrane. The membrane allows ions to pass between the channels while preventing liquid flow between them. Applying a potential to the suppressor causes ions of a specific charge to cross the membrane from the eluent flowing through the eluent channel to the regenerator flowing through the regenerator channel. This reduces the background conductivity and noise of the analytical stream while increasing the conductivity of the analyte, effectively improving the signal-to-noise ratio.

[0005] Currently, users must determine the voltage and / or current settings for the suppressor based on various parameters. These parameters include the electrolytic characteristics of a given eluent, as well as the concentration and flow rate of the eluent flowing through the suppressor. Furthermore, in existing systems, the suppressor typically requires a current higher than theoretically predicted to achieve quantitative suppression, especially when using gradients of different concentrations. For example, current systems provide users with a range of currents to apply to the suppressor, and if a lower range is insufficient to suppress the eluent, the user is typically encouraged to increase the current. Disadvantageously, higher currents often translate into heat and higher background noise, especially under high eluent concentration conditions.

[0006] In view of the foregoing, methods and systems that overcome the above and other drawbacks of known suppressors and ion chromatography systems would be beneficial. Summary of the Invention

[0007] One aspect of the present invention relates to a method for automatically adjusting a suppressor in an ion chromatography system. The method may include: setting a power supply to provide an offset voltage V to the suppressor. OS ;Activate the power supply to provide the suppressor with a voltage other than the offset voltage V OS The applied voltage waveform V A; Initiate ion chromatography operation on the ion chromatography system, wherein the eluent flows through the suppressor; During ion chromatography operation, in response to the offset and the applied voltage V OS and V A Measure the current of the suppressor; determine the suppressor state of the suppressor based on the measured current in response to the offset voltage; and / or adjust the offset voltage V based on the suppressor state. OS (a) Increasing the offset voltage V for the unsuppressed state OS (b) Maintain offset voltage V for the suppressed state OS .

[0008] Another aspect of the invention relates to a system for automatically regulating the separation of ionic substances in a liquid sample. The system may include: an ion chromatography suppressor comprising a liquid sample channel, an ion receiving channel, and an ion exchange membrane configured to substantially prevent large-volume liquid flow between the liquid sample channel and the ion receiving channel, while allowing ions with a positive or negative charge to pass between the channels; first and second electrodes electrically connected to the liquid sample channel and the ion receiving channel, respectively; a power supply for applying a potential to the suppressor via the first and second electrodes; and / or a control unit comprising one or more processors and a memory. The one or more processors run software configured to perform the following steps: setting the power supply to provide an offset voltage V to the suppressor. OS ;Activate the power supply to provide the suppressor with a voltage other than the offset voltage V OS The applied voltage V A ; Start ion chromatography run, in which the eluent flows through the suppressor; During ion chromatography run, in response to the offset and the applied voltage V OS and V A Measure the current of the suppressor; determine the suppressor state of the suppressor based on the measured current in response to the offset voltage; and / or adjust the offset voltage V based on the suppressor state. OS (a) Increasing the offset voltage V for the unsuppressed state OS (b) Maintain offset voltage V for the suppressed state OS .

[0009] Furthermore, another aspect of the present invention relates to an apparatus for automatically regulating the separation of ionic substances in a liquid sample. The apparatus may include: a power source configured to apply a potential to an ion chromatography suppressor, the suppressor comprising a liquid sample channel, an ion receiving channel, and an ion exchange membrane configured to substantially prevent large-volume fluid flow between the liquid sample channel and the ion receiving channel, while allowing ions with a positive or negative charge to pass between the channels; and / or a control unit comprising one or more processors and a memory. The one or more processors run software configured to perform the following steps: setting the power source to provide an offset voltage V to the suppressor. OS ;Activate the power supply to provide the suppressor with a voltage other than the offset voltage V OS The applied voltage waveform V A ; Start ion chromatography run, in which the eluent flows through the suppressor; During ion chromatography run, in response to the offset and the applied voltage V OS and V A Measure the current of the suppressor; determine the suppressor state of the suppressor based on the measured current in response to the offset voltage; and / or adjust the offset voltage V based on the suppressor state. OS (a) Increasing the offset voltage V for the unsuppressed state OS (b) Maintain offset voltage V for the suppressed state OS .

[0010] Embodiments of the present invention may include one or more of the following features.

[0011] As the eluent flows through the suppressor, the concentration of the eluent can change over time, and the adjustment step can change the offset voltage V in response to the change in the eluent concentration over time. OS .

[0012] A reduced upper limit current can indicate the capacitance and resistance within the suppressor, while a substantially constant current can indicate a substantially constant resistance within the suppressor.

[0013] The determination step can also be based on the measured current in response to the offset voltage, where the increased upper limit current indicates an over-suppression state. The adjustment step can also be based on the suppressor state, where the offset voltage V is reduced for over-suppression states. OS .

[0014] An oscillating voltage can have a voltage amplitude A and a voltage frequency F, and the applied voltage V A It can be a square waveform voltage with both positive and negative pulse widths. The current slope (S) is less than a first predetermined threshold value for a positive pulse width. PThis can indicate an unsuppressed state. The essentially midline current slope (S) of a positive pulse width greater than a first predetermined threshold and less than a second predetermined threshold. P This can indicate the suppression state. The current slope (S) of a positive pulse width greater than a second predetermined threshold. P It can indicate an oversuppressed state.

[0015] Applied voltage V A It can be a square waveform voltage with positive and negative pulse widths, where the positive pulse width has a slope S. P The slope S is less than 0.1 mA / s. P It can indicate the unsuppressed state, with a slope S from 0.1 mA / s to 0.3 mA / s. P It can indicate the state of inhibition and has a slope S greater than 0.3 mA / s. P It can indicate an oversuppressed state.

[0016] Applied voltage V A It can be a square waveform voltage with positive and negative pulse widths, where the negative pulse width has a slope S. N A slope S greater than -0.05 mA / s N It can indicate the unsuppressed state and a slope S less than -0.05. N It can indicate a state of suppression or oversuppression.

[0017] Applied voltage V A It can be an oscillating voltage with a period T, wherein measurement, determination, and adjustment steps are performed within each period T.

[0018] The adjustment step can adjust the offset voltage V in each cycle T. OS Adjust the voltage ΔV after adjustment. The adjusted voltage ΔV can be less than the applied voltage V. A The adjusted voltage ΔV can be less than the applied voltage V. A 10%. The adjusted voltage ΔV can be 5mV.

[0019] Increasing the upper limit current indicates the increased resistance and thermal effects within the suppressor. Furthermore, (a) a decreased upper limit current indicates the unsuppressed state of the eluent flowing through the suppressor, and (b) a substantially constant upper limit current indicates the suppressed state.

[0020] The system may further include a chromatographic column upstream of the suppressor and a conductivity detector downstream of the suppressor.

[0021] The power supply may be a dedicated power supply that provides a potential to the suppressor. The system may further include a power module that includes a power supply and a control unit. The power supply may be a dedicated power supply that provides a potential only to the suppressor.

[0022] The methods and systems of the present invention have other features and advantages that will be apparent from or set forth in more detail in the accompanying drawings and the following detailed description, which together serve to explain certain principles of the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an exemplary system for automatically adjusting an ion chromatography suppressor according to various aspects of the present invention.

[0024] Figure 2 This is a block diagram illustrating an exemplary method for automatically adjusting an ion chromatography suppressor according to various aspects of the present invention.

[0025] Figure 3 This illustrates exemplary correlations between voltage and current signals during the three impedance forms: resistance, capacitance, and inductance.

[0026] Figure 4 Exemplary voltage waveforms applied to a suppressor according to various aspects of the present invention are illustrated.

[0027] Figure 5 An exemplary evaluation of the suppressor impedance according to various aspects of the present invention is provided.

[0028] Figure 6 This is a block diagram illustrating another exemplary method for automatically adjusting an ion chromatography suppressor according to various aspects of the present invention.

[0029] Figure 7 Exemplary current response of a suppressor in response to a voltage signal applied to the suppressor, according to various aspects of the present invention. Detailed Implementation

[0030] Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings and described below. Although the invention will be described in conjunction with exemplary embodiments, it should be understood that this description is not intended to limit the invention to those exemplary embodiments. Rather, the invention is intended to cover not only exemplary embodiments but also various alternatives, modifications, equivalents, and other embodiments, all of which can be included within the spirit and scope of the invention as defined by the appended claims.

[0031] Chromatography is a separation technique in which analytes within a sample mixture are separated as they pass through a chromatographic column based on their different affinities for the stationary and mobile phases. In ion chromatography (IC), separation is ion-specific. After separation, the analytes can be detected by a conductivity detector due to the electrical properties of the ions. This inherently presents a challenge because the separated analytes are encapsulated in a sea of ​​eluent, which is also conductive, making conductive detection of the eluted analytes impossible. This challenge can be overcome by utilizing a suppressor between the separation column and the conductivity detector, which removes the background conductivity of the eluent by converting it to water, effectively enhancing the analyte signal.

[0032] The mechanisms for anion and cation analysis differ slightly. With anion suppressors, sodium or potassium ions are removed from the eluent flowing through sodium hydroxide or potassium hydroxide suppressors, respectively, and the remaining hydroxide ions combine with hydrated hydrogen ions to form water, which has extremely low conductivity and thus reduces the background signal of the eluent. The antication of the analyte is replaced by hydrated hydrogen, thereby changing the analyte from its salt form to its acidic form, thus enhancing the analyte signal. With cation suppressors, sulfite and sulfate ions are removed from the eluent flowing through sulfurous acid and sulfuric acid suppressors, respectively, and the remaining hydrated hydrogen ions combine with hydroxide ions to form water, again reducing the background signal of the eluent. Similarly, the antianion of the analyte is replaced by hydroxide, thereby changing the analyte from its salt form to its basic form, thus enhancing the analyte signal.

[0033] Over time, suppressors have evolved from single-column devices requiring multiple regeneration cycles (e.g., those described in U.S. Patents Nos. 3,897,213, 3,920,397, 3,925,019, 3,926,559, and 5,597,734) to continuously regenerating embedded devices (e.g., those described in U.S. Patent No. 4,474,664), and more recently, to electrolytic regeneration devices (e.g., those shown in U.S. Patents Nos. 4,459,357, 4,403,039, 4,999,098, and 5,248,426), the entire contents of which are incorporated herein by reference for all purposes.

[0034] Generally, voltage is applied to the suppressor to achieve ion exchange between the eluent and the regeneration channel. The amount of voltage required to adequately suppress the eluent largely depends on the eluent flow rate and concentration.

[0035] According to various aspects of the invention, the methods and systems described herein allow for the automatic adjustment of a suppressor by determining its state to distinguish between insufficient current, optimal current, or excessive current being supplied to the suppressor. The state of the suppressor can be determined based on the impedance of the suppressor, wherein capacitance can indicate an unsuppressed state, resistance can indicate a suppressed state, and resistance with a thermal effect can indicate an oversuppressed state.

[0036] Now turn to the accompanying drawings, where similar components are indicated in the various drawings by similar reference numerals. Please note... Figure 1 , Figure 1 An exemplary chromatography (IC) system 30 according to various aspects of the present invention is described. The IC system typically includes an eluent source 32, a sample injection valve 33, an ion chromatography column 35, a suppressor 37, and a conductivity detector 39. According to various aspects of the present invention, the system further includes a power supply 40 and a control unit 42, which are configured to monitor and adjust the voltage applied to the suppressor to improve or optimize the suppressor's performance. The control unit typically includes one or more processors and a memory, wherein the processor is configured to run software to perform various steps.

[0037] The power supply may be a dedicated power supply that provides a potential to the suppressor, and this configuration may be particularly suitable for retrofitting existing IC systems. The power supply and control unit may be discrete components, or they may be integrated into the power module 44, which may be provided integrally in the new IC system or separately to retrofit existing IC systems.

[0038] Generally, the sample is introduced into the eluent through sample injection valve 33, and the resulting solution flows through column 35, which is filled with chromatographic separation medium to separate the analytes within the sample from one another. The solution exiting column 35 is directed downstream of suppressor 37, which suppresses the conductivity of the eluent but does not suppress the ionic conductivity of the separated analytes.

[0039] Typically, the suppressor 37 includes: a main eluent or liquid sample channel 46 through which a sample containing ionic substances flows; and a regenerator or ion receiving channel 47 through which a regenerator flows. It will be understood that this suppressor is particularly suitable for IC suppression; however, such suppressors can also be used for sample pretreatment and other applications. Thus, the main channel can suppress eluents containing ionic substances, or alternatively, can simply pretreat liquids containing ionic substances.

[0040] The suppressed eluent is then directed downstream of a detection element, such as conductivity detector 39, for the detection of the decomposed ionic substances. In the conductivity detector, the presence of ionic substances generates an electrical signal proportional to the amount of ionic material, thus allowing the detection of the concentration of the separated ionic substances. The conductivity detector can be operatively connected to a computer, processing device, data acquisition system, or other suitable component for acquiring and / or processing data.

[0041] After passing through conductivity detector 39, the eluent can be directed to ion receiving channel 47 of suppressor 37, thereby providing water to suppressor 37 in a manner similar to that described in U.S. Patent No. 5,352,360, the entire contents of which are incorporated herein by reference for all purposes. The suppressed eluent can then be directed to waste.

[0042] To prevent degassing of the eluent in the conductivity detector 39, the system may include a backpressure coil 49 downstream of the conductivity detector, through which the eluent flows before reaching the ion receiving channel of the suppressor. The backpressure coil helps prevent degassing of gases generated during suppression, and thus prevents bubble formation in the conductivity detector, thereby reducing noise and improving detector accuracy.

[0043] As described above, the suppressor includes: a liquid sample channel 46 through which a sample containing ionic substances flows; and an ion receiving channel 47 through which a regenerant flows. An ion exchange membrane 51 between the channels is configured to substantially prevent large-scale liquid flow between the liquid sample and the ion receiving channel, while allowing ions with a positive or negative charge to pass between the channels.

[0044] The suppressor is equipped with a first electrode 53 electrically connected to a liquid sample channel 46 and a second electrode 54 electrically connected to an ion receiving channel 47. The electrodes may be in the form of flat plates or other structures that can be mounted or embedded in the respective channels. The electrodes may be formed of a highly conductive material that is inert to the solution passing through the suppressor. Platinum is a preferred material for this purpose; however, it will be understood that other suitable materials may be used. A potential is applied between the electrodes from a power source.

[0045] Power supply 40 is configured to apply a potential to suppressor 37 via first electrode 53 and second electrode 54. An external power supply can be used, such as an N6774A power supply combined with an N6705C power analyzer, both supplied by Keysight Technologies, Colorado Springs, Inc. It will be understood that other suitable power supply devices, either integrated into one or more components of system 30 or provided externally to the system, can be used.

[0046] The power supply is configured to operate or offset voltage V OSProvided to the suppressor. Besides the offset voltage V. OS In addition, the power supply is configured to transmit the applied voltage waveform V A The purpose of providing a suppressor will become apparent as described below.

[0047] In various embodiments, the power module and / or control unit can utilize engineering software for measurement, hardware control, and data insight. Suitable engineering software is LabVIEW systems engineering software, provided by National Instruments, Austin, Texas. It will be understood that this software can be equipped with a separate computing device and incorporated into the firmware of the power module and / or control unit, or integrated into other firmware or software of the IC system. It will be understood that various power supplies and control units can be utilized according to various aspects of the invention.

[0048] To determine the state of the suppressor, identifying features distinguish it from other suppressors in three main phases: (1) unsuppressed; (2) suppressed; and (3) oversuppressed. Disadvantageously, these states are difficult to assess using a conductivity detector because the conductivity signal is higher in the unsuppressed state, typically resulting in a negative peak in the presence of the analyte. The conductivity signal in the suppressed state (e.g., typically close to or less than 1.0 μS / cm) is generally acceptable, exhibiting a positive peak that identifies the analyte. Furthermore, the conductivity signal in the oversuppressed state is not easily distinguishable from that in the suppressed state, i.e., because the conductivity signal in the oversuppressed state is higher than that in the suppressed state, but typically has a similar positive peak within the same magnitude as the suppressed state conductivity signal.

[0049] Therefore, the systems and methods described herein do not rely on conductivity signals. Alternatively, and according to various aspects of the invention, the systems and methods described herein rely on the measured current signal of the suppressor itself. Furthermore, the measured current signal of the suppressor can be used to distinguish the main operating states of the suppressor based on its impedance.

[0050] According to Ohm's law, the voltage and current in a system are generally related to its impedance:

[0051] Equation (1) V=Z*I

[0052] Where V is voltage, Z is impedance, and I is current. Impedance is the opposition to current flow at a given applied voltage. There are three forms of impedance: resistance, capacitance, and inductance. In the case of pure resistance, the voltage and current signals are in phase and generally proportional to each other. In the case of capacitance, the voltage signal lags behind the current signal. And in the case of inductance, the voltage signal leads the current signal.

[0053] One way to illustrate this impedance is to apply a square voltage signal and observe the response of the current signal. For example, Figure 3 Explain the various forms of impedance. Resistive impedance has a square current signal i(t) that is very similar to the input square voltage signal V(t) – the voltage and current waveforms are in phase and proportional. Capacitive impedance has a square current signal i(t) that lags behind the input square voltage signal V(t) – here, the current signal is the derivative of the voltage signal. And inductive impedance has a leading current signal i(t) that leads the input square voltage signal V(t) – here, the current signal is the integral of the voltage signal.

[0054] Therefore, when the offset voltage V OS When applied to the suppressor to operate the suppressor, in addition to the offset voltage V OS In addition, it can also reduce the relatively small applied voltage waveform V A An applied voltage waveform V is used to monitor the current response of the suppressor to the applied voltage. This is achieved when an oscillating square waveform with frequency F and amplitude A is applied. A At that time, it can be like Figure 4 The diagram shows the combined offset and applied voltage waveforms. Furthermore, when measuring the suppressor's current, the measured current response generated from the offset voltage and applied voltage provides an indication of the suppressor's impedance and corresponding operating state.

[0055] like Figure 5 As shown, when the suppressor is not suppressed, it is highly capacitive, and the measured current response exhibits a decreasing waveform, as shown in the leftmost measured current response. Because the capacitance decreases as the suppressor approaches suppression, the measured current response exhibits a less decreasing waveform, as shown in the second measured current response from the left.

[0056] When the suppressor is appropriately suppressed, the resulting waveform is essentially a square waveform. For example... Figure 5 As shown, the measured current response in the middle is largely approximated by Figure 4 The applied voltage waveform is shown. In the suppressed state, due to the fact that the eluent is mainly water, the impedance is primarily driven by resistance. Therefore, the measured current response is essentially in phase and... Figure 4 The applied voltage wave formation ratio is shown in the figure.

[0057] In the oversuppression state, there may be additional thermal effects, such as excessive voltage, that could cause a higher current to flow through the suppressor. Since there is sufficient current during suppression, the excess current can be converted into heat, which is reflected in the upward movement of the observed measured current signal. As can be seen from the second measured current response from the right, the waveform increases slightly, while the rightmost measured current response gradually increases.

[0058] Based on the exemplary system described above, exemplary methods for an automatic adjustment IC system suppressor according to various aspects of the present invention can now be described.

[0059] refer to Figure 2 The power supply can be set to offset the oscillation voltage V. OS Provided to the suppressor. And the power supply can be activated to remove the offset voltage V. OS In addition to the applied voltage waveform V A The eluent is then supplied to the suppressor. An ion chromatography run can then be started on an IC system where the eluent flows through the suppressor.

[0060] During ion chromatography operation, in response to the offset and the applied V OS and V A The current of the suppressor is measured periodically, and the suppressor state is determined based on the measured current waveform. A decreasing current corresponding to a higher voltage waveform indicates an unsuppressed state of the eluent flowing through the suppressor, which can be attributed to the capacitance and resistance within the suppressor. A substantially constant current indicates a suppressed state, which can be attributed to the substantially constant resistance within the suppressor. Furthermore, an increasing current corresponding to a higher voltage waveform indicates an oversuppressed state, which can be attributed to the increased resistance and thermal effects within the suppressor.

[0061] The offset voltage V supplied to the suppressor can be adjusted based on the suppressor state. OS For the unsuppressed state, the offset voltage V can be increased. OS For the suppressed state, the offset voltage V can be maintained. OS Furthermore, for the over-suppression state, the offset voltage V can be reduced. OS In response to changes in the concentration of the eluent flowing through the suppressor over time, such adjustments can alter the offset voltage V. OS .

[0062] A voltage waveform can have a voltage amplitude A and a voltage frequency F, and the applied voltage waveform V A It can be a waveform voltage with positive and negative pulse widths. In various embodiments, the applied waveform voltage is used to provide easily identifiable positive and negative pulse widths, and the resulting current response signal will provide an easily identifiable current slope. A positive pulse width (S) less than a first predetermined threshold value... P The current slope can indicate the unsuppressed state, with a positive pulse width (S) greater than a first predetermined threshold and less than a second predetermined threshold. P The slope of the midline current can essentially indicate the suppression state, and the positive pulse width (S) is greater than a second predetermined threshold. P The current slope can indicate the oversuppression state.

[0063] Applied voltage V A The applied voltage can have a square waveform, which has both a positive and a negative pulse width. A It can be an oscillating voltage with a period T, wherein measurement, determination, and adjustment steps are performed for each period T. The measured current response has a positive pulse width slope S. P (For example, in) Figure 7 The slope S in P ) and negative pulse width slope S N (For example, in) Figure 7 The slope S in N According to various aspects of the invention, (a) a slope S less than approximately 0.1 mA / s P (b) Indicating an unsuppressed state, the slope S ranges from approximately 0.1 mA / s to 0.3 mA / s. P The indication is a suppressed state, and (c) is greater than a slope S of approximately 0.3 mA / s. P This indicates an oversuppressed state. And (a) the slope S is greater than approximately -0.05 mA / s. N The indication is an unsuppressed state, and (b) the slope S is less than approximately -0.05. N Indicates a state of suppression or oversuppression.

[0064] The adjustment step can adjust the offset voltage V in each cycle T. OS Adjust the adjusted voltage ΔV. In various embodiments, the adjusted voltage ΔV is less than the applied voltage V. A Furthermore, in some embodiments, the adjusted voltage ΔV is less than 10% of the amplitude A. For example, the adjusted voltage ΔV can be approximately 5mV. It will be understood that a ΔV of approximately 0.01 to 10% of the amplitude A can effectively adjust the voltage while avoiding overcorrection.

[0065] In various embodiments, the power supply and control unit can be configured in various ways to offset the voltage V. OS and the applied voltage waveform V A An application is made to the suppressor, and the suppressor's response to the offset voltage V is measured. OS and the applied voltage V A The response current.

[0066] For example, the power supply and control unit can be configured to perform similar functions. Figure 6 The described procedure is a repeating loop. This procedure allows for automatic adjustment of the offset voltage supplied to the suppressor based on the suppressor's current response, thereby creating an automatic adjustment feedback loop. The procedure can typically be run as follows:

[0067] A) Turn on the power and set the parameters;

[0068] B) Set the voltage frequency and cycle time (e.g., 0.1 Hz, cycle time of 10 seconds) to allow a single square wave to occur within the cycle (e.g., the upper portion of the resulting current wave occurs in the first 5 seconds and the lower portion occurs in the last 5 seconds).

[0069] C) After each cycle, use the current and time information from 0.01 seconds to 4.99 seconds to calculate the upslope (or S) of the current wave. P ), and from 5.01 seconds to 9.99 seconds (e.g., in mA / s) for downslope (or S N The same operation is performed, wherein the slope can be calculated by fitting the data to the best linear function with the minimum error and extracting the slope value of the linear function;

[0070] D) After each cycle, increase or decrease the offset voltage V based on the slope value. OS The upper slope (or S) is set here. P ) and downslope (or S N The preset threshold is used to increase or decrease the offset voltage accordingly.

[0071] The above is just one example of how the power supply and control unit can be configured as an operating suppressor. It will be understood that various protocols and parameters can be used to control the predetermined operating voltage (i.e., the offset voltage V). OS ) and the observable waveform of the applied voltage (i.e., the applied voltage V) A An upslope or downslope can be applied to the suppressor and the resulting current is measured to automatically adjust the suppressor. For example, the upslope or downslope can be applied individually or together (e.g., ...). Figure 7 The slope S in P and S N To assess the operating status of the suppressor.

[0072] In an exemplary experimental method according to various aspects of the present invention, the following parameters are used to apply a square waveform voltage to a Dionex circuit. TM AERS TM 500 4mm suppressor: 10-second cycle time; 0.1Hz frequency; 100mV amplitude; and a + / -5mV incremental voltage ΔV (i.e., the amount by which the offset voltage changes every 10 seconds in each cycle). Current response in Figure 7 As shown in the figure, and it can be seen that a decreased measured current response signal indicates the unsuppressed state of the suppressor, a negligible slope indicates the suppressed state, and an increased wave signal indicates the oversuppressed state.

[0073] Based on this behavior, the upper and lower slope standards of the measured current response signal can be defined to distinguish each suppressor state.

[0074] For example, the table below illustrates the slope criteria that can be used to distinguish each suppressor state.

[0075]

[0076] refer to Figure 7 When the slope (e.g., Figure 7 S in P An unsuppressed state can be identified when the upslope is below approximately 0.100 mA / s, a suppressed state can be identified when the upslope is approximately 0.100 to 0.300 mA / s, and an oversuppressed state can be identified when the upslope is above approximately 0.300 mA / s. An unsuppressed state can also be identified when the downslope (e.g., SN) is above approximately -0.050 mA / s.

[0077] For the above conditions, the voltage of the suppressor can be adjusted as follows:

[0078] A) Apply a 0.1Hz square voltage with an oscillation amplitude of 100mV and a given offset voltage to the suppressor;

[0079] B) Calculate the upslope and downslope of the obtained current signal;

[0080] C) If the downslope is greater than -0.050mA / s, the state of the suppressor is automatically classified as unsuppressed, and the offset voltage is increased by a predetermined ΔV of 5mV;

[0081] D) If the downslope is less than -0.050 mA / s, the upslope is evaluated based on the range into which the upslope falls, and the offset voltage is adjusted accordingly.

[0082] E) When the unsuppressed state is determined, the offset voltage increases by 5mV;

[0083] F) When the suppression state is determined, the offset voltage remains the same;

[0084] G) When the oversuppression state is determined, the offset voltage decreases by 5mV; and

[0085] H) The cycle repeats every 10 seconds.

[0086] It will be understood that only the upslope (e.g., Figure 7 S in P It may be able to identify the unsuppressed, suppressed, and oversuppressed states of the suppressor. It will also be understood that only the downslope (e.g., Figure 7 S in N It may be possible to identify whether the suppressor is not suppressed. Furthermore, it will be understood that the two slopes can be used together to identify the three suppressor states.

[0087] According to various aspects of the invention, the suppressor can be automatically adjusted to completely suppress the eluent and improve the accuracy of conductivity detection results by ensuring sufficient power is delivered to it. Furthermore, over-suppression can be prevented by unintentionally over-powering the suppressor, which may significantly increase the suppressor's lifespan.

[0088] The systems and methods described herein can provide simpler device configurations because the desired voltage of the suppressor can be determined without any feedback from the conductivity detector. In fact, the systems and methods described herein can supply the desired voltage to the suppressor without knowing the eluent concentration and / or the flow rate through the suppressor.

[0089] In cases of gradient or concentration changes, the systems and methods described herein allow for automatic voltage adjustments to the suppressor. For example, when the eluent concentration through the suppressor increases, applying a constant voltage to the suppressor will result in insufficient suppression of the larger eluent concentration. However, the systems and methods of the present invention allow for the identification of this unsuppressed state and the automatic implementation of corrective actions.

[0090] Since the method and system of the present invention rely solely on the measured current response of the suppressor, the power supply and / or control unit can be easily retrofitted to existing IC systems.

[0091] For ease of interpretation and precise definition in the appended claims, the terms “upper” and “lower”, and similar terms, are used to describe features of exemplary embodiments with reference to the location of such features as shown in the figures.

[0092] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and it will be apparent that many modifications and variations can be made in light of the foregoing teachings. The exemplary embodiments were chosen and described to explain certain principles of the invention and its practical application, thereby enabling those skilled in the art to make and utilize various exemplary embodiments of the invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the appended claims and their equivalents.

Claims

1. A method for automatically adjusting a suppressor in an ion chromatography system, the method comprising: Configure the power supply to provide the offset voltage VOS to the suppressor; Activate the power supply to provide the applied voltage waveform VA to the suppressor in addition to the offset voltage VOS; An ion chromatography run is started on the ion chromatography system, wherein the eluent flows through the suppressor; During the ion chromatography operation, the current of the suppressor is measured in response to the offset voltage VOS and the applied voltage VA; In response to the offset voltage, the suppressor state of the suppressor is determined based on the measured current; and The offset voltage VOS is adjusted based on the suppressor state, wherein (a) the offset voltage VOS is increased for the unsuppressed state, and (b) the offset voltage VOS is maintained for the suppressed state.

2. The method of claim 1, wherein the concentration of the eluent changes over time as the eluent flows through the suppressor, and wherein the adjustment step changes the offset voltage VOS over time in response to the change in the concentration of the eluent over time.

3. The method of claim 1, wherein (a) the reduced upper limit current indicates the capacitance and resistance within the suppressor, and (b) the substantially constant current indicates the substantially constant resistance within the suppressor.

4. The method according to claim 1, wherein: The determining step is further based on the measured current in response to the offset voltage, wherein (c) the increased upper limit current indicates an oversuppression state; and The adjustment step is also based on the suppressor state, wherein (c) the offset voltage VOS is reduced for the oversuppression state.

5. The method of claim 4, wherein the applied voltage VA has a voltage amplitude A and a voltage frequency F, and wherein the applied voltage VA is a square waveform voltage having a positive pulse width and a negative pulse width, and wherein (a) a current slope (SP) of the positive pulse width less than a first predetermined threshold indicates an unsuppressed state, (b) a substantially midline current slope (SP) of the positive pulse width greater than the first predetermined threshold and less than a second predetermined threshold indicates a suppressed state, and (c) a current slope (SP) of the positive pulse width greater than the second predetermined threshold indicates an oversuppressed state.

6. The method of claim 5, wherein the applied voltage VA is a square waveform voltage having a positive pulse width and a negative pulse width, and the positive pulse width has a slope (SP), wherein (a) a slope (SP) less than 0.1 mA / s indicates an unsuppressed state, (b) a slope (SP) from 0.1 mA / s to 0.3 mA / s indicates a suppressed state, and (c) a slope (SP) greater than 0.3 mA / s indicates an oversuppressed state.

7. The method of claim 5, wherein the applied voltage VA is a square waveform voltage having a positive pulse width and a negative pulse width, and the negative pulse width has a slope SN, wherein (a) a slope SN greater than -0.05 mA / s indicates an unsuppressed state, and (b) a slope SN less than -0.05 indicates a suppressed or oversuppressed state.

8. The method of claim 1, wherein the applied voltage VA is an oscillating voltage having a period T, wherein the measurement, determination, and adjustment steps are performed for each period T.

9. The method of claim 8, wherein the adjustment step adjusts the offset voltage VOS to the adjusted voltage ΔV in each period T.

10. The method of claim 9, wherein the adjusted voltage ΔV is less than the applied voltage VA.

11. The method of claim 10, wherein the adjusted voltage ΔV is less than 10% of the applied voltage VA.

12. The method of claim 11, wherein the adjusted voltage ΔV is 5 mV.

13. The method of claim 4, wherein the increased upper limit current indicates increased resistance and thermal effects within the suppressor.

14. The method of claim 1, wherein (a) a reduced upper limit current indicates an unsuppressed state of the eluent flowing through the suppressor, and (b) a substantially constant upper limit current indicates an suppressed state.

15. A system for automatically regulating the separation of ionic substances in a liquid sample, the system comprising: An ion chromatography suppressor comprising a liquid sample channel, an ion receiving channel, and an ion exchange membrane configured to substantially prevent large-volume liquid flow between the liquid sample channel and the ion receiving channel, while allowing ions with a positive or negative charge to pass between the channels; The first and second electrodes are electrically connected to the liquid sample channel and the ion receiving channel, respectively. A power source for applying a potential to the suppressor via the first and second electrodes; as well as A control unit comprising one or more processors and memory, wherein the one or more processors run software configured to perform the following steps: Configure the power supply to provide the offset voltage VOS to the suppressor; Activate the power supply to provide the applied voltage VA to the suppressor in addition to the offset voltage VOS; Start the ion chromatography run, with the eluent flowing through the suppressor; During the ion chromatography operation, the current of the suppressor is measured in response to the offset voltage VOS and the applied voltage VA; In response to the offset voltage, the suppressor state of the suppressor is determined based on the measured current; and The offset voltage VOS is adjusted based on the suppressor state, wherein (a) the offset voltage VOS is increased for the unsuppressed state, and (b) the offset voltage VOS is maintained for the suppressed state.

16. The system of claim 15, further comprising a chromatographic column upstream of the suppressor and a conductivity detector downstream of the suppressor.

17. The system of claim 15, wherein the power source is a dedicated power source for providing the potential to the suppressor.

18. The system of claim 15, further comprising a power module including the power supply and the control unit.

19. An apparatus for automatically regulating the separation of ionic substances in a liquid sample, the apparatus comprising: A power source is configured to apply a potential to an ion chromatography suppressor, the suppressor comprising a liquid sample channel, an ion receiving channel, and an ion exchange membrane configured to substantially prevent large-volume liquid flow between the liquid sample channel and the ion receiving channel, while allowing ions with a positive or negative charge to pass between the channels. as well as A control unit comprising one or more processors and memory, wherein the one or more processors run software configured to perform the following steps: Configure the power supply to provide the offset voltage VOS to the suppressor; Activate the power supply to provide the applied voltage waveform VA to the suppressor in addition to the offset voltage VOS; Start the ion chromatography run, with the eluent flowing through the suppressor; During the ion chromatography operation, the current of the suppressor is measured in response to the offset voltage VOS and the applied voltage VA; In response to the offset voltage, the suppressor state of the suppressor is determined based on the measured current; and The offset voltage VOS is adjusted based on the suppressor state, wherein (a) the offset voltage VOS is increased for the unsuppressed state, and (b) the offset voltage VOS is maintained for the suppressed state.

20. The apparatus of claim 19, wherein the power source is a dedicated power source for providing the potential to the suppressor.

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