Patent Description:
Ion chromatography (IC) is a widely used analytical technique for the determination of anionic and cationic analytes in various sample matrices. Typical separation columns for IC have an internal diameter ranging from about <NUM> to <NUM> millimeters and are operated at flow rates ranging from <NUM> to <NUM>/min. In an effort to improve the performance of IC, research has been performed to develop separation columns with smaller diameters. Such smaller columns are typically referred to as a capillary separation column when the internal diameter is about <NUM> millimeter or less.

In ion chromatography, dilute solutions of acids, bases, or salts are commonly used as chromatographic eluents. Traditionally, these eluents are prepared off-line by dilution with reagent-grade chemicals. Off-line preparation of chromatographic eluents can be tedious and prone to operator errors, and often introduces contaminants. For example, dilute NaOH solutions, widely used as eluents in the ion chromatographic separation of anions, are easily contaminated by carbonate. The preparation of carbonate-free NaOH eluents is difficult because carbonate can be introduced as an impurity from the reagents or by adsorption of carbon dioxide from air. The presence of carbonate in NaOH eluents can compromise the performance of an ion chromatographic method and can cause an undesirable chromatographic baseline drift during the hydroxide gradient and even irreproducible retention times of target analytes. In recent years, several approaches that utilize the electrolysis of water and charge-selective electromigration of ions through ion-exchange media have been investigated by researchers to purify or generate high-purity ion chromatographic eluents. <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, and <CIT> describe electrolytic devices that can be used to generate high purity acid and base solutions by using water as the carrier. Using these devices, high purity, contaminant-free acid or base solutions are automatically generated on-line for use as eluents in chromatographic separations.

<NPL>, reviews the operation principles of electrolytic devices that utilize the electrolysis of water and charge-selective electromigration of ions through ion-exchange media. Their applications in the ion chromatographic determination of anionic and cationic analytes are also discussed.

<CIT> discloses a method in which an acid or base is generated in an aqueous solution by the steps of: (a) providing a source of first ions adjacent an aqueous liquid in a first acid or base generation zone, separated by a first barrier (e.g., anion exchange membrane) substantially preventing liquid flow and transporting ions only of the same charge as said first ions, (b) providing a source of second ions of opposite charge adjacent an aqueous liquid in a second acid or base generation zone, separated by a second barrier transporting ions only of the same charge as the second ions, and (c) transporting ions across the first barrier by applying an electrical potential through said first and second zones to generate an acid-containing aqueous solution in one of said first or second zones and a base-containing aqueous solution in the other one which may be combined to form a salt. Also, electrolytic apparatus for performing the above method is disclosed.

In a first aspect, an electrolytic eluent generator system is provided in accordance with claim <NUM>.

In various embodiments of the first aspect, the second electrode can be a perforated electrode.

In various embodiments of the first aspect, the ion source and ion recycle module can further include a power supply configured to drive a current between the first and second electrodes such that eluent counter ions move from the eluent solution in the eluent recovery chamber to the aqueous electrolyte solution in the electrolyte reservoir.

In various embodiments of the first aspect, the eluent counter ions can include potassium ions.

In various embodiments of the first aspect, the eluent counter ions can include methanesulfonate ions.

In a second aspect, a method is provided in accordance with claim <NUM>.

In various embodiments of the second aspect, the electrolyte can include a potassium electrolyte.

In various embodiments of the second aspect, the electrolyte can include a methanesulfonate electrolyte.

In particular embodiments, the pumping can be continuous. In particular embodiments, the pumping can be intermittent. For example, pumping can periodically replace electrolytic solution in a source chamber of the electrolytic eluent generator with the solution from the electrolyte reservoir.

Although <FIG>, <FIG>, and <FIG> do not show an embodiment encompassed by the wording of the claims, they are considered as useful for understanding the invention.

Embodiments of systems and methods for ion separation are described herein.

In this detailed description of the various embodiments, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the embodiments disclosed. One skilled in the art will appreciate, however, that these various embodiments may be practiced with or without these specific details. In other instances, structures and devices are shown in block diagram form. Furthermore, one skilled in the art can readily appreciate that the specific sequences in which methods are presented and performed are illustrative and it is contemplated that the sequences can be varied and still remain within the scope of the various embodiments disclosed herein.

Unless described otherwise, all technical and scientific terms used herein have a meaning as is commonly understood by one of ordinary skill in the art to which the various embodiments described herein belongs.

<FIG> illustrates an embodiment of a chromatography system <NUM>. Chromatography system <NUM> may include a pump <NUM>, an electrolytic eluent generator <NUM>, a continuously regenerated trap column <NUM>, a degasser <NUM>, a sample injector <NUM>, a chromatographic separation device <NUM>, an electrolytic suppressor <NUM>, a detector <NUM>, and a microprocessor <NUM>. This portion of the plumbing is similar to a standard setup of the ion chromatograph. Chromatographic separation device <NUM> may be in the form of a capillary column or an analytical column. A recycle line <NUM> may be used to transfer the liquid from an output of detector <NUM> to an inlet of the electrolytic suppressor <NUM>. An optional trap <NUM> can be used to capture analyte ions. Recycle line <NUM> may be used to transfer liquid from an outlet of the regenerant channel of the electrolytic suppressor <NUM> to an inlet of an optional catalyst column <NUM> and recycle line <NUM> may be used to transfer liquid from an outlet of the optional catalyst column <NUM> to an ISIR module <NUM>. Additionally, pump <NUM> can circulate recovered eluent source ions from the ISIR module <NUM> to the eluent generator <NUM>.

Pump <NUM> can be configured to pump a liquid from a liquid source <NUM> and be fluidically connected to electrolytic eluent generator <NUM>. In an embodiment, the liquid may be deionized water, an aqueous solution with electrolyte(s), or a mixture of an organic solvent with deionized water or with aqueous electrolyte(s) solution. A few example electrolytes are sodium acetate and acetic acid. The eluent mixture that contains an organic solvent may include a water miscible organic solvent such as, for example, methanol. Pump <NUM> can be configured to transport the liquid at a pressure ranging from about <NUM> PSI to about <NUM>,<NUM> PSI. Under certain circumstances, pressures greater than <NUM>,<NUM> PSI may also be implemented. It should be noted that the pressures denoted herein are listed relative to an ambient pressure (<NUM> PSI to <NUM> PSI). Pump <NUM> may be in the form of a high-pressure liquid chromatography (HPLC) pump. In addition, pump <NUM> can also be configured so that the liquid only touches an inert portion of pump <NUM> so that a significant amount of impurities does not leach out. In this context, significant means an amount of impurities that would interfere with the intended measurement. For example, the inert portion can be made of polyether ether ketone (PEEK) or at least coated with a PEEK lining, which does not leach out a significant amount of ions when exposed to a liquid.

An eluent is a liquid that contains an acid, base, salt, or mixture thereof and can be used to elute an analyte through a chromatography column. In addition, an eluent can include a mixture of a liquid and a water miscible organic solvent, where the liquid may include an acid, base, salt, or combination thereof. Electrolytic eluent generator <NUM> is configured to generate a generant. A generant refers to a particular species of acid, base, or salt that can be added to the eluent. In an embodiment, the generant may be a base such as cation hydroxide or the generant may be an acid such as carbonic acid, phosphoric acid, acetic acid, methanesulfonic acid, or a combination thereof.

Referring to <FIG>, eluent generator <NUM> can be configured to receive the liquid from pump <NUM> and then add a generant to the liquid. The liquid containing the generant can be outputted from eluent generator <NUM> to an inlet of continuously regenerated trap column <NUM>.

Continuously regenerated trap column <NUM> is configured to remove cationic or anionic contaminants from the eluent. Continuously regenerated trap column <NUM> can include an ion exchange bed with an electrode at the eluent outlet. An ion exchange membrane stack can separate the eluent from a second electrode and contaminate ions can be swept through the ion exchange membrane stack towards the second electrode. The ion exchange membrane stack can include one or more ion exchange membranes. In various embodiments, anion removal can utilize an anion exchange bed with a cathode at the eluent outlet separated from an anode by an anion exchange membrane. Alternatively, cation removal can utilize a cation exchange bed with an anode at the eluent outlet separated from a cathode by a cation exchange membrane.

Degasser <NUM> may be used to remove residual gas. In an embodiment, a residual gas may be hydrogen and oxygen. Degasser <NUM> may include a tubing section that is gas permeable and liquid impermeable such as, for example, amorphous fluoropolymers or more specifically Teflon AF. The flowing liquid can be outputted from degasser <NUM> to sample injector <NUM> with a substantial portion of the gas removed.

Sample Injector <NUM> can be used to inject a bolus of a liquid sample into an eluent stream. The liquid sample may include a plurality of chemical constituents (i.e., matrix components) and one or more analytes of interest. The sample injector <NUM> can include an auto sampler <NUM>, a trap column <NUM> for exchanging sample counterions with regenerant ions such as hydronium or hydroxide for cation and anion applications respectively, and a multiport valve <NUM>. The auto sampler <NUM> can draw a sample from a sample container. The sample can be injected through the trap column <NUM>. The multiport valve <NUM> can be in a first position to allow the sample to fill a sample loop. After the sample loop is filled, the multiport valve can switch to a second position and the eluent stream can drive the sample onto the chromatographic separation device <NUM>.

Chromatographic separation device <NUM> can be used to separate various matrix components present in the liquid sample from the analyte(s) of interest. Typically, chromatographic separation device <NUM> may be in the form of a hollow cylinder that contains a packed stationary phase. As the liquid sample flows through chromatographic separation device <NUM>, the matrix components and target analytes can have a range of retention times for eluting off of chromatographic separation device <NUM>. Depending on the characteristics of the target analytes and matrix components, they can have different affinities to the stationary phase in chromatographic separation device <NUM>. An output of chromatographic separation device <NUM> can be fluidically connected to electrolytic suppressor <NUM>.

Electrolytic suppressor <NUM> can be used to reduce eluent conductivity background and enhance analyte response through efficient exchange of eluent counterions for regenerant ions. Electrolytic suppressor <NUM> can include an anode chamber, a cathode chamber, and an eluent suppression bed chamber separated by ion exchange membranes. The anode chamber and/or cathode chamber can produce regenerate ions or transport supplied regenerant ions. The eluent suppression bed chamber can include a flow path for the eluent separated from the regenerant by an ion exchange barrier and eluent counterions can be exchanged with regenerate ions across the ion exchange barrier. An output of electrolytic suppressor <NUM> can be fluidically connected to detector <NUM> to measure the presence of the separated chemical constituents of the liquid sample.

Detector <NUM> may be in the form of ultraviolet-visible spectrometer, a fluorescence spectrometer, an electrochemical detector, a conductometric detector, or a combination thereof. The detector <NUM> is preferably a non-destructive detector that preserves substantially the eluent stream from the suppressor eluent output.

The fluidic output of the eluent from detector <NUM> can be recycled to the regenerant channel of electrolytic suppressor <NUM> via recycle line <NUM> after optionally passing through a trap column <NUM> for trapping the analyte ions. The trap column can be configured to remove analyte ions while passing the liquid and any remaining eluent ions through to the electrolytic suppressor <NUM>. The fluidic output of the electrolytic suppressor <NUM> which contains the eluent ions can be sent to an optional catalyst column <NUM>. The catalyst column <NUM> can recombine hydrogen and oxygen gas to form water in an eluent stream. Additionally, the catalyst column can reduce any residual electrolysis byproducts such as hydrogen peroxide. The fluidic output of the catalyst column <NUM> can be sent to the ISIR module <NUM>.

ISIR module <NUM> can be configured to receive the liquid from optional catalyst column <NUM> or electrolytic suppressor <NUM> and then remove the generant ions from the liquid. The liquid, after a significant reduction in generate concentration can be outputted from ISIR module <NUM> to waste. The generant can be combined with the source solution. To achieve this, the ISIR module <NUM> can include an ion exchange membrane stack separating a generant source solution from the liquid stream. The ion exchange membrane stack can include one or more ion exchange membranes. A current from power supply <NUM> can be applied to electrodes on either side of the ion exchange membrane to selectively drive generant ions from the liquid through the ion exchange membrane and into the generant source solution.

Pump <NUM> can circulate the generant source solution between the ISIR module <NUM> and the eluent generator <NUM> to continuously supply the eluent generator <NUM> with fresh generant source solution for the addition of generant ions into the eluent stream. Thus, a self-sustaining source of the generant source solution can be achieved as per the present invention. In various embodiments, the pump <NUM> can continuously circulate the generant source solution, intermittently circulate the generant source solution, or replace the generant source solution in the eluent generator <NUM> with fresh generant source solution from the ISIR module <NUM> in batches periodically.

An electronic circuit may include microprocessor <NUM>, a timer, and a memory portion. In addition, the electronic circuit may include a power supply that are configured to apply a controlling signal, respectively. Microprocessor <NUM> can be used to control the operation of chromatography system <NUM>. Microprocessor <NUM> may either be integrated into chromatography system <NUM> or be part of a personal computer that communicates with chromatography system <NUM>. Microprocessor <NUM> may be configured to communicate with and control one or more components of chromatography system such as pump <NUM>, pump <NUM>, eluent generator <NUM>, sample injector <NUM>, detector <NUM>, and ISIR module <NUM>. The memory portion may be used to store instructions to set the magnitude and timing of the current waveform with respect to the switching of sample injector <NUM> that injects the sample.

One advantage of the present invention is the ISIR module <NUM> in conjunction with the eluent generator <NUM> can be miniaturized in terms of dimensions. Prior commercial versions of the eluent generator cartridge have been designed to maximize the usage by having a relatively large volume of the eluent concentrate at a high concentration. Typically, the volume ranges from <NUM> to <NUM> and the concentration ranges from <NUM> to <NUM> of the source reagent. In contrast, in the present disclosure, since the generant is constantly recycled into the ISIR and this action ensures that the source supply to the eluent generator is maintained and the eluent generator can operate without any downtime. The preferable concentration of the eluent generator in the present application can be in the <NUM> concentration and at a volume of about <NUM>. Similarly, the ISIR module can have a volume of <NUM>. The concentration in the ISIR can be also start at <NUM>. Thus, a large reduction in footprint of the eluent generator and the ISIR module is feasible.

In various embodiments, the ion removal, such as in continuously regenerated trap column <NUM> and optional trap <NUM>, can be accomplished by using packed bed columns. Other multichannel membrane-based devices can also be applied for this function. When using membrane-based devices, a recycled deionized water stream will be used for this operation. The packed bed devices may need to be replaced periodically. Membrane-based devices can be continuously operated but can require a separate water stream for operation. If complete recycle of the eluent is not desired, then the effluent from the ISIR recycle channel can be routed to the regenerant channels of the membrane-based devices. When complete recycle is desired then the outlet from the recycle channel can be routed to the deionized water reservoir for recycling the deionized water since after the recycle aspect the stream should be free of any ions.

<FIG> illustrates the operation principle of an ISIR module <NUM>. The ISIR module <NUM> can include an eluent recovery chamber <NUM> and an electrolyte reservoir <NUM>.

The eluent recovery chamber <NUM> can contain a perforated platinum (Pt) electrode <NUM>. The electrolyte reservoir <NUM> can contain a Pt electrode <NUM> and a recovered electrolyte solution. In various embodiments, the ISIR module <NUM> can recover a cation electrolyte, such as potassium ions, electrode <NUM> can be an anode where hydronium ions can be formed from electrolysis, and electrode <NUM> can be a cathode where hydroxide ions can be formed. In other embodiments, the ISIR module <NUM> can recover ions, such as phosphate ions, acetate ions, and methanesulfonate ions, electrode <NUM> can be a cathode where hydroxide ions can be formed, and electrode <NUM> can be an anode where hydronium ions can be formed. The eluent recovery chamber <NUM> can be connected to the electrolyte reservoir <NUM> by means of an exchange connector <NUM> which can permit the passage of ions of only one charge, either anions or cations, from the eluent recovery chamber <NUM> into the electrolyte reservoir <NUM>.

In various embodiments, where the ISIR module <NUM> is recovering cations, the exchange connector <NUM> can permit the passage of cations while substantially preventing the passage of anions from the eluent recovery chamber <NUM> to the electrolyte reservoir <NUM>. In alternate embodiments where the electrolytic ISIR module <NUM> is recovering anions, the exchange connector <NUM> can permit the passage of anions while substantially preventing the passage of cations from the eluent recovery chamber <NUM> to the electrolyte reservoir <NUM>.

The electrolyte reservoir <NUM> can include outlet <NUM> to transport recovered electrolyte solution to the eluent generator and inlet <NUM> to receive depleted electrolyte solution from the eluent generator. In various embodiments, the electrolytic reservoir <NUM> can be partially filled with fluid such that the is a fluid-filled portion and a gas-filled portion contained in the electrolyte reservoir <NUM>. The outlet <NUM> can withdrawal solution from the fluid filled portion. The inlet <NUM> can supply the fluid within either the gas-filled portion or the fluid-filled portion. Placement of the inlet <NUM> and outlet <NUM> can be such that fluid entering through the inlet <NUM> thoroughly mixed with the solution with the electrolyte reservoir <NUM> before reaching the outlet <NUM>.

In various embodiments, the eluent recovery chamber can be packed with ion exchange screens or resins or monolithic material or combinations thereof to maximize transfer of the regenerant ions.

To recover a KOH eluent, the eluent can move through the eluent recovery chamber <NUM> and a current can be applied between the electrode <NUM> and electrode <NUM>. Under the applied electric field, the electrolysis of water can occur at both the electrode <NUM> and electrode <NUM> of the device <NUM>. Water can be oxidized to form H+ ions and oxygen gas at the electrode <NUM> in the eluent recovery chamber <NUM>: H2O → <NUM>+ + <NUM>/<NUM> O2↑+ 2e-. Water can be reduced to form OH- ions and hydrogen gas at the electrode <NUM> in the electrolyte reservoir <NUM>: <NUM> H2O + 2e-→ <NUM> OH- + H2↑. As H+ ions, generated at the anode <NUM> it consumes the hydroxide ions in the eluent to form water while K+ ions in the eluent migrates across the cation exchange connector <NUM> into the electrolyte reservoir <NUM>. These K+ ions can combine with hydroxide ions generated at the cathode <NUM> to produce the KOH solution, which can be used by the eluent generator as a source of K+ ions. The reduction in concentration of K+ in the eluent can be proportional to the current applied to the ISIR module <NUM> and the flow rate through the eluent recovery chamber <NUM>.

To recover a methanesulfonic acid eluent, the eluent can move through the eluent recovery chamber <NUM> and a current can be applied between the electrode <NUM> and electrode <NUM>. Under the applied electric field, the electrolysis of water can occur at both the electrode <NUM> and electrode <NUM> of the device <NUM>. Water can be oxidized to form H+ ions and oxygen gas at electrode <NUM> in the electrolyte reservoir <NUM>: H2O -> <NUM>+ + <NUM>/<NUM> O2↑+ 2e-. Water can be reduced to form OH- ions and hydrogen gas at electrode <NUM> in the eluent recovery chamber <NUM>: <NUM> H2O + 2e-→ <NUM> OH- + H2↑. As OH- ions, generated at the electrode <NUM> it consumes the hydronium ions in the eluent to form water while methanesulfonate ions in the eluent recovery chamber <NUM> migrates across the anion exchange connector <NUM> into the electrolyte reservoir <NUM>. These methanesulfonate ions can combine with hydronium ions generated at the electrode <NUM> to produce the methanesulfonic acid solution, which can be used by the eluent generator as a source of methanesulfonate ions. The concentration of generated methanesulfonic acid can be proportional to the current applied to the ISIR module <NUM> and the flow rate through the eluent recovery chamber <NUM>.

<FIG> illustrates an embodiment of a chromatography system <NUM> where ions are selectively removed from the sample prior to combining with the eluent. Chromatography system <NUM> may include a pump <NUM>, an electrolytic eluent generator <NUM>, a continuously regenerated trap column <NUM>, a degasser <NUM>, a sample injector <NUM>, a chromatographic separation device <NUM>, an electrolytic suppressor <NUM>, a detector <NUM>, and a microprocessor <NUM>. Chromatographic separation device <NUM> may be in the form of a capillary column or an analytical column. A recycle line <NUM> may be used to transfer the liquid from an output of detector <NUM> to an inlet of the selective ion removal <NUM>. An optional trap <NUM> can be used to capture analyte ions. Recycle line <NUM> may be used to transfer liquid from an outlet of selective ion removal <NUM> to an inlet of the electrolytic suppressor <NUM>, recycle line <NUM> may be used to transfer liquid from an outlet of electrolytic suppressor <NUM> to an inlet of an optional catalyst column <NUM>, and recycle line <NUM> may be used to transfer liquid from an outlet of the optional catalyst column <NUM> to an ISIR module <NUM>. Additionally, pump <NUM> can circulate recovered eluent ions from the ISIR module <NUM> to the eluent generator <NUM>.

Sample Injector <NUM> can be used to inject a bolus of a liquid sample into an eluent stream. The liquid sample may include a plurality of chemical constituents (i.e., matrix components) and one or more analytes of interest. The sample injector <NUM> can include an auto sampler <NUM>, selective ion removal <NUM>, and a multiport valve <NUM>. The auto sampler <NUM> can draw a sample from a sample container. The sample can be provided to the selective ion removal which can selectively remove counter ions but leave analyte ions in the sample. The multiport valve <NUM> can be in a first position to allow the sample to fill a sample loop. After the sample loop is filled, the multiport valve can switch to a second position and the eluent stream can drive the sample onto the chromatographic separation device <NUM>.

The fluidic output of the eluent from detector <NUM> can be recycled to the selective ion removal <NUM> via recycle line <NUM> after optionally passing through a trap column <NUM>. The trap column can be configured to remove analyte ions while passing the treated liquid. The fluidic output of the selective ion removal <NUM> can be recycled to the electrolytic suppressor <NUM> via recycle line <NUM>. The fluidic output of the electrolytic suppressor <NUM> can be sent to an optional catalyst column <NUM> via recycle line <NUM>. The catalyst column <NUM> can recombine hydrogen and oxygen ions to form water. The fluidic output of the catalyst column <NUM> can be sent to the ISIR module <NUM> via recycle line <NUM>.

<FIG> illustrates an embodiment of a chromatography system <NUM> where the fluidic output of the ISIR module is used as a source of liquid to a <NUM>-channel electrolytic eluent generator. Chromatography system <NUM> may include a pump <NUM>, an electrolytic eluent generator <NUM>, a sample injector <NUM>, a chromatographic separation device <NUM>, an electrolytic suppressor <NUM>, a detector <NUM>, and a microprocessor <NUM>. Chromatographic separation device <NUM> may be in the form of a capillary column or an of detector <NUM> to an inlet of the electrolytic suppressor <NUM>. An optional trap <NUM> can be used to capture analyte ions. Recycle line <NUM> may be used to transfer liquid from an outlet of electrolytic suppressor <NUM> to an inlet of an optional catalyst column <NUM> and recycle line <NUM> may be used to transfer liquid from an outlet of the optional catalyst column <NUM> to an ISIR module <NUM>. Additionally, pump <NUM> can circulate recovered eluent ions from the ISIR module <NUM> to the eluent generator <NUM>.

Pump <NUM> can be configured to pump a liquid from an outlet of the ISIR module <NUM> and be fluidically connected to electrolytic eluent generator <NUM>. The electrolytic eluent generator <NUM> can be a <NUM>-channel electrolytic eluent generator. In various embodiments, the <NUM>-channel electrolytic eluent generator can include an inner channel separated from a first outer channel by a cation exchange membrane and a second outer channel by an anion exchange member. A current can be applied to drive reagent ions from the first outer channel into the inner channel and counter ions from the second outer channel into the inner channel, thus generating the eluent in the inner channel. Advantageously, since the electrodes are placed in the outer channels, any gas formation at the electrodes (H<NUM> or O<NUM>) does not reach the inner channel, eliminating the need for a degasser. Such devices are illustrated in <CIT>, with one exemplary example from <FIG> of <CIT> as described above. Such devices can find utility in the present invention. Additionally, a continuously regenerated trap column can also be eliminated.

The fluidic output of the eluent from detector <NUM> can be recycled to electrolytic suppressor <NUM> via recycle line <NUM> after optionally passing through a trap column <NUM>. The trap column can be configured to remove analyte ions while passing the liquid and any remaining eluent ions through to the electrolytic suppressor <NUM>. The fluidic output of the electrolytic suppressor <NUM> can be sent to an optional catalyst column <NUM>. The catalyst column <NUM> can recombine hydrogen and oxygen ions to form water. The fluidic output of the catalyst column <NUM> can be sent to the ISIR module <NUM>.

ISIR module <NUM> can be configured to receive the liquid from optional catalyst column <NUM> or electrolytic suppressor <NUM> and then remove the generant from the liquid. The liquid, after a significant reduction in generate concentration can be output from ISIR module <NUM> and used as a liquid source for eluent generator <NUM> as it is primarily water with the ions substantially removed. An optional reservoir can also be placed (not shown) to collect the liquid source. The generant can be added to a source solution. To achieve this, the ISIR module <NUM> can include an ion exchange membrane separating a generant source solution from the liquid stream. A current from power supply <NUM> can be applied to electrodes on either side of the ion exchange membrane to drive generant ions from the liquid through the membrane and into the generant source solution.

<FIG> illustrates an embodiment of a chromatography system <NUM> using a <NUM> or <NUM> channel ISIR module. Chromatography system <NUM> may include a pump <NUM>, an electrolytic eluent generator <NUM>, a continuously regenerated trap column <NUM>, a degasser <NUM>, a sample injector <NUM>, a chromatographic separation device <NUM>, an electrolytic suppressor <NUM>, a detector <NUM>, and a microprocessor <NUM>. Chromatographic separation device <NUM> may be in the form of a capillary column or an analytical column. A recycle line <NUM> may be used to transfer the liquid from an output of detector <NUM> to an ISIR module <NUM>. Additionally, pump <NUM> can circulate recovered eluent ions from the ISIR module <NUM> to the eluent generator <NUM>.

The fluidic output of the eluent from detector <NUM> can be directed to ISIR module <NUM> via line <NUM> after optionally passing through a trap column <NUM>.

ISIR module <NUM> can be a <NUM>-channel module as depicted in <FIG> or <FIG>channel module. In various embodiments, a <NUM>-channel ISIR module can include an inner channel separated from a first outer channel by a cation exchange membrane and a second outer channel by an anion exchange member to recovery potassium ions from a potassium hydroxide stream. A current can be applied to drive reagent ions from the first outer channel (containing the eluent from the detector <NUM>) into the inner channel and counter ions from the inner channel into the second outer channel, thus recycling the reagent ions into the inner channel which can be pumped to the eluent generator <NUM>. The output in this example from the first outer channel is pure water in this embodiment and can be used as the source of the deionized water for the eluent generator.

ISIR module <NUM> can be configured to receive the liquid from electrolytic suppressor <NUM> or optional catalyst column <NUM> and then remove the generant from the liquid. The liquid, after a significant reduction in generate concentration can be outputted from ISIR module <NUM> to conductivity detector <NUM>. The generant can be added to a source solution. To achieve this, the ISIR module <NUM> can include an ion exchange membrane separating a generant source solution from the liquid stream. A current from power supply <NUM> can be applied to electrodes on either side of the ion exchange membrane to drive generant ions from the liquid through the membrane and into the generant source solution.

<FIG> illustrates a method of recycling eluent counter ions from an eluent stream. At <NUM>, the eluent stream can be provided to the eluent recovery chamber. At <NUM>, a current can be supplied to the electrodes of the ISIR. At <NUM>, the current can cause water to be electrolytically split at the electrodes of the ISIR, and, at <NUM>, eluent counter ions can migrate from the eluent stream in the eluent recovery chamber to the electrolyte reservoir. At <NUM>, the electrolyte solution containing the recovered eluent counter ions can be circulated from the ISIR to an electrolytic eluent generator. Depleted electrolyte solution can be circulated back to the ISIR to be refreshed with recovered eluent counter ions.

Claim 1:
An electrolytic eluent generator system comprising:
an electrolytic eluent generator (<NUM>) including:
an electrolyte reservoir including:
a source chamber containing an aqueous electrolyte solution, the source chamber including a first inlet and a first outlet; and
a third electrode;
an eluent generation chamber including a fourth electrode; and
a second ion exchange connector including a second ion exchange membrane stack, the second ion exchange connector between the electrolyte reservoir and the eluent generation chamber;
an ion source and ion recycle module (<NUM>, <NUM>) comprising: a first electrolyte reservoir (<NUM>) including:
a chamber containing an aqueous electrolyte solution including an electrolyte, the chamber having a chamber inlet (<NUM>) and a chamber outlet (<NUM>), the chamber inlet (<NUM>) fluidically connected to the source chamber of the electrolytic eluent generator (<NUM>) and configured to receive depleted electrolyte solution from the source chamber of the electrolytic eluent generator, the chamber outlet (<NUM>) fluidically connected to the source chamber of the electrolytic eluent generator (<NUM>) and
configured to provide recycled electrolyte solution to the electrolytic eluent generator source chamber; and a first electrode (<NUM>);
an eluent recovery chamber (<NUM>) including a second electrode (<NUM>) and configured to receive an eluent solution including eluent counter ions from the eluent generator; and
an ion exchange connector (<NUM>) including an ion exchange membrane stack, the ion exchange connector coupling the first electrolyte reservoir (<NUM>) and the eluent recovery chamber (<NUM>);
a pump (<NUM>) configured to circulate the aqueous electrolyte solution between the source chamber of the electrolyte reservoir of the electrolytic eluent generator (<NUM>) and the chamber of the first electrolyte reservoir (<NUM>) of the ion source and ion recycle module (<NUM>, <NUM>); and characterised in that the electrolytic eluent generator system further comprises a pump (<NUM>) fluidically connected between an outlet of the eluent recovery chamber (<NUM>) of the ion source and ion recycle module (<NUM>) and the electrolytic eluent generator (<NUM>), and configured to circulate a liquid to the eluent generation chamber of the electrolytic eluent generator (<NUM>).