Electrolytic eluent generator with stable operating voltage

Abstract

An electrolytic eluent generator comprises an electrolyte reservoir, an eluent generating chamber and an ion exchange membrane stack. The electrolyte reservoir comprises: a chamber containing an aqueous electrolyte solution, the aqueous electrolyte solution comprising an electrolyte and a surfactant; and a first electrode. The eluent generating chamber comprises a second electrode. The ion exchange connector comprises an ion exchange membrane stack and a compression block.

Description

Technical Field

[0001] The present disclosure relates generally to the field of ion chromatography comprising an electrolytic eluent generator having a stable operating voltage. Background Art

[0002] Ion chromatography (IC) is a widely used analytical technique for determining anionic and cationic analytes in various sample matrices. The internal diameter of a typical separation column of IC ranges from about 2 mm to 4 mm and operates at a flow rate ranging from 0.2 mL / min to 3 mL / min. In order to improve the performance of IC, research has been performed to develop separation columns with smaller diameters. When the internal diameter is about 1 mm or less, such smaller columns are generally referred to as capillary separation columns.

[0003] In ion chromatography, dilute solutions of acids, bases or salts are usually used as chromatographic eluents. Traditionally, these eluents are prepared offline by dilution with reagent-grade chemicals. Offline preparation of chromatographic eluents can be tedious and prone to operator error, and often introduces contaminants. For example, dilute NaOH solutions widely used as eluents in ion chromatography separation of anions are easily contaminated by carbonates. The preparation of carbonate-free NaOH eluents is difficult because carbonates can be introduced from reagents as impurities, or can be introduced by absorbing carbon dioxide from the air. The presence of carbonates in NaOH eluents may impair the performance of ion chromatography methods, and may cause undesirable chromatographic baseline drifts during the irreproducible retention time of hydroxide gradients and even target analytes. In recent years, researchers have studied several methods that utilize the electrolysis of water and the charge-selective electromigration of ions through ion exchange media to purify or generate high-purity ion chromatography eluents. U.S. Patent Nos. 6,036,921, 6,225,129, 6,316,271, 6,316,270, 6,315,954 and 6,682,701 describe electrolytic devices that can be used to generate high-purity acid and base solutions by using water as a carrier. Using these devices, high-purity, non-polluting acid or base solutions are automatically generated online for use as eluents in chromatographic separations. Summary of the invention

[0004] In a first aspect, an electrolytic eluent generator may include an electrolyte reservoir, an eluent generation chamber, and an ion exchange connector. The electrolyte reservoir may include: a chamber containing an aqueous electrolyte solution, the aqueous electrolyte solution including an electrolyte and a surfactant; and a first electrode. The eluent generation chamber may include a second electrode. The ion exchange connector may include an ion exchange membrane stack and a compression block.

[0005] In various embodiments of the first aspect, the eluent generating chamber can be configured to operate at a pressure of up to about 15,000 psi.

[0006] In various embodiments of the first aspect, the second electrode can be a porous cathode.

[0007] In various embodiments of the first aspect, the compression block can be positioned between the electrolyte reservoir and the ion exchange membrane stack, and the compression block can include a plurality of channels.

[0008] In various embodiments of the first aspect, the surfactant can be: (a) an anionic surfactant, and the ion exchange membrane stack can have a net negative charge and can be configured to allow cations to flow through and block anions and a large amount of liquid flow; or (b) a cationic surfactant, and the ion exchange membrane stack can have a net positive charge and can be configured to allow anions to flow through and block cations and a large amount of liquid flow.

[0009] In various embodiments of the first aspect, the surfactant can be a nonionic surfactant.

[0010] In various embodiments of the first aspect, the surfactant can be a surfactant that is stable under caustic and acidic conditions.

[0011] In a second aspect, a method may include providing an aqueous electrolyte solution comprising an electrolyte and a surfactant to an electrolyte reservoir, the electrolyte reservoir being coupled to an eluent generation chamber via an ion exchange connector. The ion exchange connector may include an ion exchange membrane stack and a compression block. The method may further include applying a voltage or current across a first electrode in the eluent generation chamber and a second electrode in the electrolyte reservoir; electrolytically decomposing water at the first electrode to form hydroxide anions or hydronium ions in the eluent generation chamber; and migrating ions from the electrolyte reservoir through the ion exchange membrane stack to the eluent generation chamber to combine with the hydroxide anions to form a cationic hydroxide solution, or to combine with the hydronium ions to form an anionic acid solution for ion chromatography.

[0012] In various embodiments of the second aspect, the electrolyte may include a potassium electrolyte.

[0013] In various embodiments of the second aspect, the electrolyte may include a methanesulfonate electrolyte.

[0014] In various embodiments of the second aspect, the surfactant can be: (a) an anionic surfactant, and the ion exchange membrane stack can have a net negative charge and can be configured to allow cations to flow through and block anions and a large amount of liquid flow; or (b) a cationic surfactant, and the ion exchange membrane stack can have a net positive charge and can be configured to allow anions to flow through and block cations and a large amount of liquid flow.

[0015] In various embodiments of the second aspect, the surfactant can be a nonionic surfactant.

[0016] In various embodiments of the second aspect, the surfactant can be a surfactant that is stable under caustic and acidic conditions.

[0017] In various embodiments of the second aspect, the concentration of the surfactant can be between about 1 ppm and about 100 ppm.

[0018] In various embodiments of the second aspect, the eluent generating chamber can be at a pressure of up to about 15,000 psi.

[0019] In various embodiments of the second aspect, the current across the anode and the cathode can produce a voltage that remains within a range of no greater than about + / - 2.0 V for at least 7 days.

[0020] In various embodiments of the second aspect, the current across the anode and the cathode can produce a voltage that varies by no more than 10% of a starting voltage over at least 7 days.

[0021] In various embodiments of the second aspect, the compressed mass can include a plurality of channels, and the method can further include generating bubbles in the electrolyte reservoir, wherein the bubbles do not adhere to the plurality of channels.

[0022] In a third aspect, an electrolytic eluent generator may include an electrolyte reservoir, an eluent generation chamber, and an ion exchange connector. The electrolyte reservoir may include: a chamber containing an aqueous electrolyte solution; and a first electrode. The eluent generation chamber may include a second electrode. The ion exchange connector may include an ion exchange membrane stack and a compressed block, the compressed block including a surface-modified polymer having a hydrophilic surface.

[0023] In various embodiments of the third aspect, the aqueous electrolyte solution may include a potassium electrolyte.

[0024] In various embodiments of the third aspect, the aqueous electrolyte solution may include a methanesulfonate electrolyte.

[0025] In various embodiments of the third aspect, the surface-modified polymer is a chemically modified polymer. In specific embodiments, the chemically modified polymer can be chemically modified using sodium borohydride. In specific embodiments, the chemically modified polymer can be modified by converting a ketone functional group into an alcohol functional group. In specific embodiments, the chemically modified polymer can comprise an alcohol-functionalized polyetheretherketone (PEEK-OH).

[0026] In various embodiments of the third aspect, the surface modified polymer can be a polymer treated with oxygen plasma. In certain embodiments, the polymer treated with oxygen plasma can contain alcohol and carbonyl functional groups.

[0027] In various embodiments of the third aspect, the eluent generating chamber is configured to operate at a pressure of at most about 15,000 psi.

[0028] In various embodiments of the third aspect, the second electrode can be a porous cathode.

[0029] In various embodiments of the third aspect, the compression block can be positioned between the electrolyte reservoir and the ion exchange membrane stack, and the compression block can include a plurality of channels.

[0030] In a fourth aspect, a method may include providing an aqueous electrolyte solution to an electrolyte reservoir, the electrolyte reservoir being coupled to an eluent generation chamber via an ion exchange connector. The ion exchange connector may include an ion exchange membrane stack and a compression block. The compression block may include a surface-modified polymer having a hydrophilic surface. The method may further include applying a current or voltage across a first electrode in the eluent generation chamber and a second electrode in the electrolyte reservoir; electrolytically decomposing water at the cathode to form hydroxide anions or hydronium ions in the eluent generation chamber; and migrating ions from the electrolyte reservoir through the ion exchange membrane stack to the eluent generation chamber to combine with the hydroxide anions to form a cationic hydroxide solution, or to combine with the hydronium ions to form an anionic acid solution for ion chromatography.

[0031] In various embodiments of the fourth aspect, the aqueous electrolyte solution may include a potassium electrolyte.

[0032] In various embodiments of the fourth aspect, the aqueous electrolyte solution may include a methanesulfonate electrolyte.

[0033] In various embodiments of the fourth aspect, the surface-modified polymer can be a chemically modified polymer. In specific embodiments, the chemically modified polymer can be chemically modified using sodium borohydride. In specific embodiments, the chemically modified polymer can be modified by converting a ketone functional group into an alcohol functional group. In specific embodiments, the chemically modified polymer can comprise an alcohol-functionalized polyetheretherketone (PEEK-OH).

[0034] In various embodiments of the fourth aspect, the surface-modified polymer can be an oxygen plasma-modified polymer. In certain embodiments, the oxygen plasma-treated polymer can contain alcohol and carbonyl functional groups.

[0035] In various embodiments of the fourth aspect, the eluent generating chamber is at a pressure of at most about 15,000 psi.

[0036] In various embodiments of the fourth aspect, the current across the anode and the cathode can produce a voltage that remains within a range of no greater than about + / - 2.0 V for at least 7 days.

[0037] In various embodiments of the fourth aspect, the current across the anode and the cathode can produce a voltage that varies by no more than 10% of a starting voltage over at least 7 days.

[0038] In various embodiments of the fourth aspect, the compressed mass can include a plurality of channels, and the method can further include generating bubbles in the electrolyte reservoir, wherein the bubbles do not adhere to the plurality of channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] For a more complete understanding of the principles disclosed herein and its advantages, the following description is now made with reference to the accompanying drawings, in which:

[0040] Figure 1 A chromatography system including an eluent generator according to various embodiments is presented.

[0041] Figure 2A and 2B An eluent generator according to various embodiments is shown.

[0042] Figure 3 Chemical modification of PEEK according to various examples is demonstrated.

[0043] Figure 4 and 5 Methods of chemically modifying membrane compression blocks for eluent generators are presented in accordance with various embodiments.

[0044] Figure 6Methods of operating a chemically modified eluent generator according to various embodiments are presented.

[0045] Figure 7 Methods of operating an eluent generator using a surfactant according to various embodiments are presented.

[0046] Figure 8 The operating voltage profile of the unmodified electrolytic KOH generator is shown.

[0047] Fig. 9 The operating voltage profile of an electrolytic KOH generator with a PEEK membrane compressed block component modified with dimethyl sulfoxide (DMSO) containing sodium borohydride is shown.

[0048] Fig.10 The operating voltage profile of an electrolytic KOH generator using oxygen plasma modification having a PEEK film compressed block component is shown.

[0049] Fig.11 The separation of seven common anions is demonstrated, comparing the results obtained using an unmodified electrolytic KOH generator with the results using an electrolytic KOH generator modified using oxygen plasma with a PEEK membrane compression block component.

[0050] Fig.12 Reproduction of the separation of fluoride and phosphate using an electrolytic KOH generator modified with oxygen plasma using a PEEK membrane compression block component is demonstrated.

[0051] Fig.13 The operating voltage profile of an electrolytic KOH generator treated with TERGITOL MIN foam having a PEEK film compression block component is shown.

[0052] Fig.14 The operating voltage profile of an electrolytic KOH generator treated with TRITON H55 having a PEEK film compressed block component is shown.

[0053] It should be understood that the drawings are not necessarily drawn to scale, nor are the relationships between the objects in the drawings necessarily drawn to scale. The drawings are intended to make the various embodiments of the devices, systems, and methods disclosed herein clear and easy to understand. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. Moreover, it should be understood that the drawings are not intended to limit the scope of the present teachings in any way. DETAILED DESCRIPTION

[0054] Embodiments of systems and methods for ion separation are described herein.

[0055] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in any way.

[0056] In this detailed description of the various embodiments, for the purpose of explanation, many specific details are set forth to provide a thorough understanding of the disclosed embodiments. However, those skilled in the art will appreciate that the various embodiments may be practiced with or without these specific details. In other cases, the structures and devices are shown in block diagram form. In addition, those skilled in the art can readily appreciate that the particular order of presentation and execution methods is illustrative, and it is contemplated that the order may be changed and still remain within the spirit and scope of the various embodiments disclosed herein.

[0057] All literature and similar materials cited in this application, including but not limited to patents, patent applications, papers, books, monographs, and internet web pages, are expressly incorporated by reference in their entirety for any purpose. Unless otherwise described, all technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which the various embodiments described herein belong.

[0058] It should be understood that there is an implicit "about" before the temperature, concentration, time, pressure, flow rate, cross-sectional area, etc. discussed in the present teachings, so that slight and insubstantial deviations are within the scope of the present teachings. In this application, unless otherwise specifically stated, the use of the singular includes the plural. Moreover, the use of "comprise (comprises or comprises)", "contain (contains or contains)" and "include (includes or includes)" is not intended to be restrictive. It should be understood that both the foregoing general description and the following detailed description are merely exemplary and explanatory and do not limit the present teachings.

[0059] As used herein, "a" or "an" may also mean "at least one" or "one or more". Moreover, the use of "or" is inclusive, such that the phrase "A or B" is true when "A" is true, "B" is true, or both "A" and "B" are true. In addition, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

[0060] A "system" describes a set of real or abstract components, comprising a whole, in which each component interacts with or is related to at least one other component within the whole.

[0061] Chromatography system

[0062] Figure 1 An embodiment of a chromatography system 100 is shown. The chromatography system 100 may include a pump 102, an electrolytic eluent generator 104, a continuously regenerated trap column 106, a degasser 108, a sample injector 110, a chromatographic separation device 112, an electrolytic suppressor 114, a detector 116, and a microprocessor 118. The chromatographic separation device 112 may take the form of a capillary column or an analytical column. A recirculation line 120 may be used to transfer liquid from the output of the detector 116 to the inlet of the electrolytic suppressor 114, a recirculation line 122 may be used to transfer liquid from the outlet of the electrolytic suppressor 114 to the inlet of the degasser 108, and a recirculation line 124 may be used to transfer liquid from the outlet of the degasser 108 to the inlet of the continuously regenerated trap column 106.

[0063] Pump 102 can be configured to pump liquid from liquid source 124 and fluidly connected to electrolytic eluent generator 104. In one embodiment, liquid can be deionized water, aqueous solution with one or more electrolytes or mixture of organic solvent and deionized water or with one or more aqueous electrolyte solutions. Several example electrolytes are sodium acetate and acetic acid. Eluent mixture containing organic solvent can contain water-miscible organic solvent, such as methanol. Pump 102 can be configured to deliver liquid with a pressure ranging from about 20PSI to about 15,000PSI. In some cases, the pressure greater than 15,000PSI can also be implemented. It should be noted that the pressure indicated herein is listed relative to ambient pressure (13.7PSI to 15.2PSI). Pump 102 can take the form of a high pressure liquid chromatography (HPLC) pump. In addition, pump 102 can also be configured so that liquid only contacts the inert part of pump 102, so that a significant amount of impurities will not be filtered out. In this context, significant means the amount of impurities that will interfere with the expected measurement results. For example, the inert portion may be made of polyetheretherketone (PEEK) or at least coated with a PEEK lining that does not leach out significant amounts of ions when exposed to liquids.

[0064] Eluent is a liquid containing acid, alkali, salt or its mixture, and can be used for eluting analyte by chromatographic column. In addition, eluent can comprise a mixture of liquid and water miscible organic solvent, wherein the liquid can comprise acid, alkali, salt or its combination. Electrolytic eluent generator 104 is configured to generate product. Product refers to the acid, alkali or salt of the specific species that can be added to the eluent. In one embodiment, product can be alkali, such as cationic hydroxide, or product can be acid, such as carbonic acid, phosphoric acid, acetic acid, methanesulfonic acid or its combination.

[0065] Reference Figure 1The eluent generator 104 may be configured to receive the liquid from the pump 102 and then add the product to the liquid. The liquid containing the product may be output from the eluent generator 104 to the inlet of the continuously regenerated trap column 106.

[0066] The continuously regenerated capture column 106 is configured to remove cation or anion pollutants from the eluent. The continuously regenerated capture column 106 can be included in an ion exchange bed with an electrode at the eluent outlet. The ion exchange membrane interface can separate the eluent from the second electrode, and the pollutant ions can be swept through the ion exchange membrane toward the second electrode. In various embodiments, anion removal can utilize anion exchange bed, wherein the cathode at the eluent outlet is separated from the anode by anion exchange membrane. Alternatively, cation removal can utilize cation exchange bed, wherein the anode at the eluent outlet is separated from the cathode by cation exchange membrane. Pollutant ions can be filtered out from the regenerated capture column 106 using recycled liquid through the recirculation line 124 located downstream of the degasser assembly 108.

[0067] Degasser 108 can be used to remove residual gas. In one embodiment, the residual gas can be hydrogen and oxygen. Degasser 108 can include a gas permeable and liquid impermeable pipeline section, such as an amorphous fluoropolymer or more specifically Teflon AF. The flowing liquid can be output from the degasser 108 to a sample injector 110 where a significant portion of the gas is removed. The gas can be filtered out from the degasser 108 using a recirculating liquid through a recirculation line 122 downstream of the electrolytic suppressor 114. The recirculated liquid containing the residual gas can also be output from the degasser 108 and directed to the continuously regenerated capture column 106.

[0068] The sample injector 110 can be used to inject a large dose of a liquid sample into the eluent stream. The liquid sample can contain a variety of chemical components (ie, matrix components) and one or more analytes of interest.

[0069] The chromatographic separation device 112 can be used to separate various matrix components present in the liquid sample from one or more analytes of interest. Typically, the chromatographic separation device 112 can take the form of a hollow cylinder containing a filled stationary phase. When the liquid sample flows through the chromatographic separation device 112, the matrix components and the target analyte can have a certain range of retention times to elute from the chromatographic separation device 112. According to the characteristics of the target analyte and the matrix components, they can have different affinities to the stationary phase in the chromatographic separation device 112. The output of the chromatographic separation device 112 can be fluidically connected to an electrolytic suppressor 114.

[0070] Electrolytic suppressor 114 can be used to reduce eluent conductivity background and enhance analyte response by effectively exchanging eluent counter ions for regenerant ions. Electrolytic suppressor 114 can include an anode chamber, a cathode chamber, and an eluent suppression bed chamber separated by an ion exchange membrane. The anode chamber and / or cathode chamber can produce regenerative ions. The eluent suppression bed chamber can include a flow path for an eluent separated from the regenerant by an ion exchange barrier, and the eluent counter ions can be exchanged with the regenerative ions across the ion exchange barrier. The cathode chamber or the anode chamber can be supplied with recirculated liquid by a recirculation line 120 located downstream of the conductivity detector 116. The output of the electrolytic suppressor 114 can be fluidically connected to the detector 116 to measure the presence of the separated chemical components of the liquid sample.

[0071] like Figure 1 As shown in FIG, the fluid output of the eluent from the detector 116 is recycled to the electrolytic suppressor 114 through the recycling line 120, the fluid output of the electrolytic suppressor 114 is recycled to the degasser 108 through the recycling line 122, the fluid output of the degasser 108 is recycled to the continuously regenerated trap column 106 through the recycling line 124, and the fluid output of the continuously regenerated trap column 106 flows to waste.

[0072] Detector 116 can take the form of an ultraviolet-visible spectrometer, a fluorescence spectrometer, an electrochemical detector, a conductivity detector, a charge detector or a combination thereof. Details on charge detectors based on charged barriers and two electrodes can be found in U.S. Pre-authorization Publication No. 20090218238, which is fully incorporated herein by reference. For situations where a recirculation line 120 is not required, detector 116 can also take the form of a mass spectrometer or a charged aerosol detector. The charged aerosol detector sprays the effluent flow and produces charged particles, which can be measured as a current proportional to the analyte concentration. Details on the charged aerosol detector can be found in U.S. Patent Nos. 6,544,484 and 6,568,245, which are fully incorporated herein by reference.

[0073] The electronic circuit may include a microprocessor 118, a timer, and a memory portion. In addition, the electronic circuit may include a power supply configured to apply control signals respectively. The microprocessor 118 may be used to control the operation of the chromatographic system 100. The microprocessor 118 may be integrated into the chromatographic system 100 or as a part of a personal computer that communicates with the chromatographic system 100. The microprocessor 118 may be configured to communicate and control one or more components of the chromatographic system, such as pump 102, eluent generator 104, sample injector 110, and detector 116. The memory portion may be used to store instructions to set the magnitude and timing of the current waveform relative to the switching of the sample injector 110 that injects the sample.

[0074] Figure 2A The operating principle of the electrolysis generator cartridge 200 is shown. The cartridge may include a high pressure eluent generation chamber 202 and a low pressure electrolyte reservoir 204. In various embodiments, the high pressure generation chamber 202 may operate at a pressure of up to about 15,000 psi, such as between about 2000 psi and about 10,000 psi.

[0075] The eluent generation chamber 202 may contain a porous platinum (Pt) electrode 206. The electrolyte reservoir 204 may contain a Pt electrode 208 and an electrolyte solution. In various embodiments, the electrolysis generator box 200 may produce a base, such as KOH, the electrode 206 may be a cathode that can form hydroxide ions, and the electrode 208 may be an anode. In other embodiments, the electrolysis generation box 200 may produce an acid, such as carbonic acid, phosphoric acid, acetic acid, methanesulfonic acid, the electrode 206 may be an anode that can form hydronium ions, and the electrode 208 may be a cathode. The eluent generation chamber 202 may be connected to the electrolyte reservoir 204 via an exchange connector 210, which may allow ions of only one charge to be transferred from the electrolyte reservoir 204 to the high pressure generation chamber 202. The exchange connector 210 may also play a key role as a high pressure physical barrier between the low pressure electrolyte reservoir 204 and the high pressure generation chamber 202. In various embodiments, where the electrolysis generator cartridge 200 is a base generator, the swap connector 210 can allow the transfer of cations while substantially preventing the transfer of anions from the electrolyte reservoir 204 to the generation chamber 202. In alternative embodiments where the electrolysis generator cartridge 200 is an acid generator, the swap connector 210 can allow the transfer of anions while substantially preventing the transfer of cations from the electrolyte reservoir 204 to the generation chamber 202.

[0076] To generate the KOH eluent, deionized water may be pumped through the eluent generation chamber 202, and a DC current may be applied between the electrode 208 and the electrode 206. Under the applied electric field, electrolysis of the water may occur at both the electrode 208 and the electrode 206 of the device 200. The water may be oxidized at the electrode 208 in the electrolyte reservoir 204 to form H+ ions and oxygen gas: H2O→2H++1 / 2O2↑+2e-. The water may be reduced at the electrode 206 in the KOH generation chamber 202 to form OH- ions and hydrogen gas: 2H2O+2e-→2OH-+H2↑. When the H+ ions generated at the anode 206 replace the K in the electrolyte reservoir 204, the water may be oxidized to form OH- ions and hydrogen gas: 2H2O+2e-→2OH-+H2↑. + ions, the displaced ions can migrate across the cation exchange connector 210 into the eluent generating chamber 202. + The ions can be combined with the hydroxide ions generated at cathode 206 to produce a KOH solution, which can be used as an eluent for anion exchange chromatography. The concentration of the generated KOH can be determined by the current applied to the generator cartridge 200 and the carrier water flow rate through the generation chamber 202.

[0077] To generate the methanesulfonic acid eluent, deionized water may be pumped through the eluent generation chamber 202, and a DC current may be applied between the electrode 208 and the electrode 206. Under the applied field, electrolysis of the water may occur at both the electrode 208 and the electrode 206 of the device 200. The water may be oxidized at the electrode 206 in the KOH generation chamber 202 to form H+ ions and oxygen gas: H2O→2H++1 / 2O2↑+2e-. The water may be reduced at the electrode 208 in the electrolyte reservoir 204 to form OH- ions and hydrogen gas: 2H2O+2e-→2OH-+H2↑. When the OH generated at the electrode 206 is - When the ions replace the methanesulfonate ions in the electrolyte reservoir 204, the replaced ions can migrate across the anion exchange connector 210 into the eluent generation chamber 202. These methanesulfonate ions can combine with the hydronium ions generated at the electrode 206 to produce a methanesulfonic acid solution, which can be used as an eluent for cation exchange chromatography. The concentration of the generated methanesulfonic acid can be determined by the current applied to the generator cartridge 200 and the carrier water flow rate through the generation chamber 202.

[0078] Figure 2BA cross-sectional view of an electrolytic generator 200 is shown. The stack of ion exchange membranes 212 is supported by a PEEK compression block 214 so that the generation chamber 202 can withstand high pressure. In various embodiments, the PEEK compression block 214 can be porous with open vertical channels that can generally be cylindrical. The electrolyte solution in the low-pressure electrolyte reservoir 204 is in direct contact with the ion exchange membrane stack 212 through the open vertical channels 216 of the PEEK membrane compression block 214.

[0079] During operation of the electrolysis generator 202, oxygen gas may be generated at the anode positioned in the electrolyte reservoir 204. Most of the oxygen gas rises and dissipates through the exhaust port from the low-pressure electrolyte reservoir 204. However, some oxygen gas may dissolve in the alkaline solution and may gather to form bubbles. These oxygen bubbles may adhere to the hydrophobic surfaces of the low-pressure electrolyte reservoir 204 and the PEEK film compression block 214, and some of the bubbles may settle and block the open vertical channels 216 of the PEEK film compression block 214.

[0080] If the open vertical channels of the PEEK membrane compression block 214 are blocked by oxygen bubbles, the contact between the electrolyte solution in the low-pressure electrolyte reservoir 204 and the ion exchange membrane stack 212 can be reduced or lost. Therefore, the migration of ions across the cation exchange membrane stack 212 in the electrolyte reservoir 204 to the eluent generation chamber 202 can be limited thereby, resulting in an increase in the operating voltage of the electrolysis generator 200. Higher operating voltages may result in higher operating wattages, as well as potentially excessive amounts of heat generated during the operation of the electrolysis generator 202. Excessive amounts of heat may result in damage to the ion exchange membrane 212, and may be detrimental to the reliable operation of the electrolysis eluent generator 202. It is necessary to develop new embodiments of the electrolysis eluent generator, which can avoid the influence of bubbles that can adhere to the hydrophobic surfaces of the open vertical channels 216 of the low-pressure electrolyte reservoir 204 and the PEEK membrane compression block 214.

[0081] Bubbles in aqueous solutions have a tendency to adhere to solid surfaces, such as the surfaces of the low pressure electrolyte reservoir 204 and the PEEK membrane compression block 214. The contact angle of the bubble on the solid surface depends on the hydrophobicity of the solid surface. On a hydrophilic surface, the contact angle of the bubble can generally be less than 90°, and on a hydrophobic surface, the contact angle of the bubble can generally be greater than 90°. The amount and size of bubbles adhering to a hydrophilic surface in an aqueous solution can be significantly reduced compared to a hydrophobic surface in an aqueous solution.

[0082] Chemical modification

[0083] An embodiment of an electrolytic eluent generator constructed using high-strength polymer components is described, in which the surface is modified to be hydrophilic to reduce and minimize the amount and size of oxygen bubbles adhering to the surface of the low-pressure electrolyte reservoir and the PEEK membrane compression block. The surface-modified electrolytic eluent generator can eliminate the blockage of the open vertical channels of the PEEK membrane compression block, can maintain continuous fluid contact between the electrolyte solution in the low-pressure electrolyte reservoir and the ion exchange membrane stack, and can thereby provide stabilization of the operating voltage of the electrolytic KOH generator and improvement of the operational reliability.

[0084] The hydrophobic surface of the PEEK membrane compression block can be obtained by using Figure 3 The sodium borohydride-containing dimethyl sulfoxide (DMSO) shown in FIG. 5 chemically modifies the PEEK surface into a hydrophilic surface by converting the ketone functional groups of PEEK into alcohol functional groups (PEEK-OH).

[0085] Figure 4 A method 400 for chemically modifying a compressed block of PEEK film is shown. At 402, a modification solution can be prepared. For example, sodium borohydride and dimethyl sulfoxide can be added to a flask under magnetic bar stirring, and an argon-enclosed atmosphere can be applied. The flask can be heated in an oil bath, for example at 120°C. After the sodium borohydride is completely dissolved, the compressed block of PEEK film can be treated as indicated at 404. For example, a component can be added to the flask. In various embodiments, reacting the component with the modification solution can continue for 4 hours or more. At 406, the component can be removed from the modification solution, and at 408, the component can be washed. For example, after cooling to room temperature, the DMSO solution can be discarded, and the PEEK component can be washed twice with isopropanol and three times with acetone, respectively. After washing the component, the electrolytic KOH eluent generator box can be assembled as indicated at 410.

[0086] Figure 5 A method 500 is shown for modifying a hydrophobic surface of a PEEK membrane compression block using an oxygen plasma treatment to form a hydrophilic surface comprising alcohol and carbonyl functional groups on the PEEK surface. At 502, the PEEK membrane compression block component can be washed. For example, DI H 2 O The PEEK film compression block components are rinsed thoroughly and then oven dried overnight. At 504, the components can be treated. For example, the components can be placed in a plasma chamber of a plasma cleaner / disinfector for oxygen plasma treatment. In various embodiments, the oxygen plasma treatment can be performed with a high level of oxygen plasma for 60 minutes at a time, where the plasma treatment is repeated three times. At 506, the oxygen plasma treated components can be used to assemble an electrolytic KOH eluent generator box.

[0087] Figure 6 A method 600 of operating a chemically modified electrolytic eluent generator is shown. At 602, a K + An electrolytic eluent generator is prepared with an electrolyte solution such as an ionic electrolyte solution. At 604, a voltage can be applied to the electrolytic eluent generator, and at 606, the electrolytic eluent generator can produce an electrolytic eluent. In various embodiments, the current across the anode and the cathode will produce a voltage that remains within a range of about + / -2.0V, such as within a range of about + / -1.0V, or even within a range of about + / -0.5V over a period of at least 7 days. In various embodiments, the current across the anode and the cathode will produce a voltage that does not vary by more than about 10% of the starting voltage over at least 7 days. At 608, the electrolytic eluent can be used to perform chromatographic separation.

[0088] Surfactants

[0089] In another preferred embodiment of the electrolytic eluent generator, a surfactant containing ionic or hydrophilic functional groups can be used to coat the PEEK surface to reduce and minimize the amount and size of oxygen bubbles adhering to the surface of the low-pressure electrolyte reservoir and the PEEK membrane compression block. In this embodiment, a small amount of surfactant can be added to the electrolyte solution. The surfactant should be chemically stable in the electrolyte solution and cannot migrate across the ion exchange membrane stack under the applied electric field.

[0090] In various embodiments, the surfactant can be an ionic surfactant or a nonionic surfactant. In a particular embodiment, when used in a base generator, such as for the generation of KOH, the ionic surfactant can be an anionic surfactant. Alternatively, the cationic surfactant can be a suitable ionic surfactant for an acid generator, such as for the generation of methanesulfonic acid. In addition, the surfactant can be stable in caustic or acidic solutions.

[0091] In various embodiments, the concentration of the surfactant may be between about 1 ppm and about 100 ppm.

[0092] Figure 7 A method 700 of operating an electrolytic eluent generator with a surfactant is shown. At 702, a surfactant can be added to an electrolyte solution, and at 704, a surfactant such as K +The electrolytic eluent generator is prepared by using an electrolyte solution such as an ionic electrolyte solution. For example, the electrolyte solution can be mixed with a nonionic surfactant, such as TERGITOL MIN foam. In another example, when the eluent is an alkali, the electrolyte solution can be mixed with an anionic surfactant, such as TRITONH55, and the ion exchange membrane stack can have a net negative charge, and can be configured to allow cations to flow through and block anions and a large amount of liquid flow. In another example, when the eluent is an acid, the electrolyte solution can be mixed with a cationic surfactant, and the ion exchange membrane stack can have a net positive charge, and can be configured to allow anions to flow through and block cations and a large amount of liquid flow. Advantageously, the ion exchange membrane stack can prevent surfactants from contaminating the eluent. At 706, a voltage can be applied to the electrolytic eluent generator, and at 708, the electrolytic eluent generator can produce an electrolytic eluent. In various embodiments, the current across the anode and cathode will produce a voltage that is maintained within a range of about + / -2.0V, such as about + / -1.0V, for a period of at least 7 days. In various embodiments, the current across the anode and cathode produces a voltage that does not vary by more than about 10% of the starting voltage over at least 7 days. At 710, a chromatographic separation can be performed using an electrolytic eluent.

[0093] Although the present teachings are described in conjunction with various embodiments, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be understood by those skilled in the art.

[0094] In addition, in describing various embodiments, this specification may have presented methods and / or processes in the form of a specific sequence of steps. However, to the extent that the method or process does not rely on the specific sequence of steps set forth herein, the method or process should not be limited to the specific sequence of steps described. As will be appreciated by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of steps set forth in this specification should not be interpreted as a limitation to the claims. In addition, claims for the method and / or process should not be limited to performing their steps in the order written, and those of ordinary skill in the art can easily understand that the sequence can be changed and the sequence still remains within the spirit and scope of the various embodiments.

[0095] result

[0096] Figure 8An example of an operating voltage profile of an unmodified electrolytic KOH generator under the conditions of 1.5 mL / min, 60 mM KOH and 4150 psi is shown. The box operating voltage remained relatively stable within one day of continuous operation. However, thereafter, the box operating voltage began to climb from about 12 V to over 35 V, which resulted in excessive amounts of heat being generated during operation of the electrolytic KOH eluent generator.

[0097] Fig. 9 The typical operating voltage profile of the electrolytic KOH eluent generator using a PEEK membrane compressed block component obtained by converting the PEEK ketone functional group into an alcohol functional group using dimethyl sulfoxide (DMSO) containing sodium borohydride is shown. Under the conditions of 1.5 mL / min, 60 mM KOH, 3550 psi, the device operating voltage is stable, ranging from 15.7 V to 16.5 V during 7 days of continuous operation. That is, the voltage varies within a range of about + / - 0.5 V and less than 10% of the starting voltage.

[0098] Fig.10 The typical operating voltage profile of the electrolytic KOH eluent generator using the PEEK membrane compressed block component modified by oxygen plasma is shown, and under the conditions of 1.5 mL / min, 60 mM KOH, 3995 psi, the device operating voltage is stable, ranging from 14.5 V to 15.5 V during 10 days of continuous operation. That is, the voltage is maintained within a range of about + / - 0.5 V and less than 10% of the starting voltage.

[0099] Fig.11 The separation of 7 common anions (see Table 1 for anion concentration) on a DIONEX IONPAC AS11-HC 4μm column is shown. The results show that the same separation effect is obtained using a standard DIONEX EGC 500KOH box and a modified DIONEX EGC-500KOH box assembled using a PEEK membrane compression block treated with oxygen plasma. The test conditions are 1.5mL / min, 30mM KOH, 4200psi, 15min / run and 10μL injection. The baseline is shifted on the y-axis to provide a comparison of retention time and peak shape. The results show that surface modification by oxygen plasma treatment does not affect the performance of the DIONEXEGC-500KOH box.

[0100] Table 1: Analytes used to compare modified and unmodified KOH generators

[0101] peak Analytes concentration 1 <![CDATA[F - ]]> 2mg / L 2 <![CDATA[Cl - ]]> 10mg / L 3 <![CDATA[NO 2 - ]]> 10mg / L 4 <![CDATA[SO 4 2- ]]> 10mg / L 5 <![CDATA[Br - ]]> 10mg / L 6 <![CDATA[NO 3 - ]]> 10mg / L 7 <![CDATA[PO 4 3- ]]> 20mg / L

[0102] Fig.12The separation of fluorine (2 mg / L) and phosphate (20 mg / L) on a DIONEX IONPAC AS11-HC 4 μm column obtained using a DIONEX EGC 500KOH box is shown, which is assembled using a PEEK membrane compression block treated with oxygen plasma. The test conditions are 1.5 mL / min, 60 mM KOH, 4350 psi, 60 min / run and 10 μL injection. The baseline is shifted on the y axis to provide a comparison of retention time and peak shape. The results show that excellent retention time reproducibility of the target analyte is obtained in 400 consecutive runs.

[0103] Fig.13 An overlay of the operating voltages obtained for a DIONEXEGC 500KOH cell assembled using a compressed block of PEEK film treated with TERGITOL MIN foam is shown. Under conditions of 1.5 mL / min, 60 mM KOH, 4150 psi, the device operating voltage was stable, ranging from 11.5 V to 13.5 V during 12 days of continuous operation. That is, the voltage remained within a range of approximately + / - 1.0 V and less than 10% of the starting voltage.

[0104] Fig.14 An overlay of the operating voltages obtained for a DIONEX EGC 500KOH cell assembled using TRITON H55 (anionic surfactant) treated with a PEEK film compression block is shown. Under the conditions of 1.5 mL / min, 60 mM KOH, 3950 psi, the device operating voltage was stable, ranging from 12 V to 13.4 V during 7 days of continuous operation. That is, the voltage remained within a range of about + / - 1.0 V and less than 10% of the starting voltage.

Claims

1. An electrolytic eluent generator, comprising: An electrolyte reservoir, the electrolyte reservoir comprising: a chamber containing an aqueous electrolyte solution comprising an electrolyte and a surfactant; as well as a first electrode; an eluent generating chamber, the eluent generating chamber comprising a second electrode; as well as An ion exchange connector, the ion exchange connector comprising: Ion exchange membrane stack; as well as A compressed block, wherein the compressed block comprises a surface-modified polymer having a hydrophilic surface, the polymer being PEEK.

2. The electrolytic eluent generator according to claim 1, wherein the surface-modified polymer is a chemically modified polymer.

3. The electrolytic eluent generator according to claim 2, wherein the chemically modified polymer is chemically modified using sodium borohydride.

4. The electrolytic eluent generator of claim 2, wherein the chemically modified polymer is modified by converting ketone functional groups into alcohol functional groups.

5. The electrolytic eluent generator of claim 2, wherein the chemically modified polymer comprises alcohol-functionalized polyetheretherketone (PEEK-OH).

6. The electrolytic eluent generator according to claim 1, wherein the surface-modified polymer is a polymer treated with oxygen plasma.

7. The electrolytic eluent generator of claim 6, wherein the oxygen plasma treated polymer comprises alcohol and carbonyl functional groups.

8. The electrolytic eluent generator of claim 1, wherein the eluent generating chamber is configured to operate at a pressure of up to 15,000 psi.

9. The electrolytic eluent generator of claim 1, wherein the compression block is disposed between the electrolyte reservoir and the ion exchange membrane stack, and the compression block comprises a plurality of channels.

10. A method comprising: providing an aqueous electrolyte solution comprising electrolyte to an electrolyte reservoir, the electrolyte reservoir being coupled to an eluent generation chamber via an ion exchange connector comprising an ion exchange membrane stack and a compression block comprising a surface-modified polymer having a hydrophilic surface, the polymer being PEEK; applying a voltage or current across a first electrode in the eluent generating chamber and a second electrode in the electrolyte reservoir; electrolytically decomposing water at the first electrode to form hydroxide anions or hydronium ions in the eluent generating chamber; as well as Ions are migrated from the electrolyte reservoir through the ion exchange membrane stack to the eluent generation chamber to combine with the hydroxide anions to form a cationic hydroxide solution, or with the hydronium ions to form an anionic acid solution for use in ion chromatography.

11. The method of claim 10, wherein the electrolyte comprises a potassium electrolyte.

12. The method of claim 10, wherein the electrolyte comprises a methanesulfonate electrolyte.

13. The method of claim 10, wherein the eluent generating chamber is at a pressure of at most 15,000 psi.

14. The method of claim 10, wherein the current across the anode and cathode produces a voltage that remains within a range of no greater than + / - 2.0 V for at least 7 days.

15. The method of claim 10, wherein the current across the anode and cathode produces a voltage that does not vary by more than 10% of the starting voltage over at least 7 days.

16. The method of claim 10, wherein the compressed mass comprises a plurality of channels, and the method further comprises generating gas bubbles in the electrolyte reservoir, wherein the gas bubbles do not adhere to the plurality of channels.

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