Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
  • G01N30/96—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation using ion-exchange
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
  • B01D15/08—Selective adsorption, e.g. chromatography
  • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
  • B01D15/16—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to the conditioning of the fluid carrier
  • B01D15/166—Fluid composition conditioning, e.g. gradient
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/30—Polyalkenyl halides
  • B01D71/32—Polyalkenyl halides containing fluorine atoms
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J47/00—Ion-exchange processes in general; Apparatus therefor
  • B01J47/02—Column or bed processes
  • B01J47/06—Column or bed processes during which the ion-exchange material is subjected to a physical treatment, e.g. heat, electric current, irradiation or vibration
  • B01J47/08—Column or bed processes during which the ion-exchange material is subjected to a physical treatment, e.g. heat, electric current, irradiation or vibration subjected to a direct electric current
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J47/00—Ion-exchange processes in general; Apparatus therefor
  • B01J47/12—Ion-exchange processes in general; Apparatus therefor characterised by the use of ion-exchange material in the form of ribbons, filaments, fibres or sheets, e.g. membranes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J49/00—Regeneration or reactivation of ion-exchangers; Apparatus therefor
  • B01J49/50—Regeneration or reactivation of ion-exchangers; Apparatus therefor characterised by the regeneration reagents
  • B01J49/57—Regeneration or reactivation of ion-exchangers; Apparatus therefor characterised by the regeneration reagents for anionic exchangers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/14—Alkali metal compounds
  • C25B1/16—Hydroxides
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/22—Inorganic acids
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B13/00—Diaphragms; Spacing elements
  • C25B13/04—Diaphragms; Spacing elements characterised by the material
  • C25B13/08—Diaphragms; Spacing elements characterised by the material based on organic materials
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
  • G01N30/02—Column chromatography
  • G01N30/26—Conditioning of the fluid carrier; Flow patterns
  • G01N30/28—Control of physical parameters of the fluid carrier
  • G01N30/34—Control of physical parameters of the fluid carrier of fluid composition, e.g. gradient
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
  • G01N30/96—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation using ion-exchange
  • G01N2030/965—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation using ion-exchange suppressor columns

Definitions

• the present invention relates to an ion transport barrier, particularly one used for an ion transport device such as one for generating a high-purity acid, base, or salt or for a suppressor in an ion chromatography system.
• liquid chromatography In liquid chromatography, a liquid sample containing a number of components to be separated is directed through a chromatography separator, typically an ion exchange resin bed. The components are separated on elution from the bed in a solution of eluent.
• a chromatography separator typically an ion exchange resin bed.
• ions to be detected in the sample consisting of ions in an aqueous solution, are separated in a chromatography separator, such as a chromatography column, using an eluent containing an acid or a base and, thereafter, sent to a suppressor, followed by detection, typically by an electrical conductivity detector.
• the electrical conductivity of the electrolyte is suppressed but not that of the separated ions, so that the latter may be detected by the conductivity detector.
• One such suppressor disclosed in US Patent No. 6,325,976, is continuous and electrolytic. Suppression is in a packed bed of ion exchange resin.
• Other suppressors are disclosed in U.S. Patents 4,999,098, 4,500,430, 4,647,380 and 5,352,360. There, the suppressor is in the form of a membrane suppressor in which a regenerant solution flows on one side of an ion exchange membrane and the sample stream flows on the other side.
• a convenient source of high-purity acid, base, or salt for use as an eluent for liquid chromatography and, particularly, for ion chromatography is disclosed in U.S. Patents 5,045,204 and 6,225,129.
• a cation or anion source is disposed in a flowing or non-flowing cation or anion source reservoir.
• aqueous liquid flows through a base- or acid-generation chamber separated from the source reservoir by an ion exchange barrier, in the form of an ion exchange membrane, substantially blocking liquid flow across it while providing a cation or anion transport bridge.
• Electrical potential is applied to electrolytically generate hydroxide or hydronium ions in the base or acid generation chamber.
• the acid or base generation apparatus of US Patents 6,225,129 or 5,045,204 or devices described in US Patent Application 20060211125 are ion transport apparatus in which ions are transported across an ion exchange membrane.
• an ion transport barrier comprising a wall with a bead seat and an ion exchange bead sealed in the bead seat.
• the bead is capable of passing ions of one charge, positive or negative, and of substantially blocking bulk liquid flow.
• ion transport apparatus in which ions of one charge, positive or negative, in a liquid in a first or second chamber are transported to a liquid in the other of the first or second chambers through a barrier which blocks bulk liquid flow between the first and second chambers.
• the apparatus comprises a first chamber and an adjacent second chamber having an inlet and an outlet, and a first wall separating said first and second chambers.
• the first wall comprises a first ion exchange bead sealed in a first bead seat in said first wall.
• the first ion exchange bead is capable of passing ions of one charge, positive or negative, and of blocking bulk liquid flow.
• Specific ion transport apparatuses include electrolytic eluent generator and a suppressor for ion chromatography.
• a suppressor comprises an ion receiving flow channel and an adjacent liquid sample flow-through channel having an inlet and an outlet, and a first wall separating said ion receiving flow channel and said sample flow-through channel.
• the first wall comprises a first ion exchange bead sealed in a bead seat in said first wall, said first ion exchange bead being capable of passing ions of one charge, positive or negative, and of blocking bulk liquid flow.
• a method which includes transporting ions of one charge, positive or negative, in a liquid in a first chamber to liquid in a second chamber through a barrier which blocks liquid flow between the first and second chambers.
• the method comprises providing a first ion source containing a selected ion of one charge, positive or negative, in a first chamber, flowing an ion receiving liquid stream through an ion receiving flow channel adjacent said first chamber, and providing a first wall separating said first chamber from said ion receiving flow channel, said first wall comprising a first ion exchange bead sealed in a bead seat in said first wall.
• the selected ion is transported from said ion source to said flowing ion receiving stream through the first ion exchange bead.
• Such method can be for suppression of a liquid for ion chromatography or as a method for generating an acid or a base.
• One embodiment of a suppression method comprises providing an ion receiving flow channel and an adjacent liquid sample flow-through channel having an inlet and an outlet, providing a first wall separating said ion receiving flow channel and said sample flow-through channel.
• the first wall comprises a first ion exchange bead sealed in a bead seat in said first wall.
• the first ion exchange bead is capable of passing ions of one charge, positive or negative, and of blocking bulk liquid flow.
• the selected ions are suppressed by transporting said selected ions from said sample stream flow channel through said first ion exchange bead into said ion receiving flow channel.
• Another embodiment is an electrolytic method for generating an acid or a base.
• the method comprises providing an anion or a cation source in an aqueous liquid in an anion or cation source reservoir in a first chamber, and flowing an aqueous liquid stream through an acid or base generation chamber which is separated from the anion or cation source reservoir by a first wall separating said first chamber and said acid or base generation flow-through channel.
• the first wall comprises a first ion exchange bead sealed in a bead seat in said first wall.
• the first ion exchange bead is capable of passing ions of one charge, positive or negative, and of substantially blocking bulk liquid flow.
• An electrical potential is applied between said anion or cation source reservoir and said acid or base generation chamber, respectively, through said ion exchange bead.
• the anion or cation from said anion or cation source reservoir is transported through said first ion exchange bead into said acid or base generation chamber to electrolytically generate an acid, base, or salt.
• Figures 1 and 2 are schematic representations of ion transport apparatus according to the invention.
• Figure 3a and 3b arc top and side views, respectively, of a bead array barrier according to the present invention.
• Figure 4a is a side view of a bead array barrier; and Figure 4b is an enlarged cross- sectional view of one bead in a bead seat of the bead array barrier of Figure 4a.
• Figure 5 is a graph showing current-voltage-concentration behavior of high pressure bead-based electrodialytic generator, 4 M KOH in both cathode and anode chambers.
• Figure 6 is a chromatogram performed by low-pressure planar membrane eluent generator, 10 mM KOH anode feed, cathode feed water. 75 ⁇ m x 5 m fused silica column coated with AS 11 latex, flow rate 1.5 ⁇ L/min. Sample 200 picoequivalents of each anion in 20 nL. Lower chromatogram isocratic, 2.1 mM KOH eluent. Actual gradient profile for upper gradient chromatogram is shown in the figure.
• Method and apparatus of the present invention are applicable to ion transport apparatus and methods, particularly ones for generating a chromatography eluent and for ion chromatography suppression such as set forth above, specifically by replacing an ion exchange membrane barrier with a wall seating an ion exchange bead. Also, it is applicable to generation of an eluent for liquid chromatography other than ion chromatography which does not use a suppressor and which uses a different detector, e.g. an ultraviolet (UV) detector.
• the eluent may be in a form (e.g., salt) other than an acid or base.
• the term "aqueous stream" includes pure water or water with such additives.
• the terms "eluent comprising a base,” “eluent comprising an acid,” an “acid” or a “base” meets an aqueous stream including acid or base generated in the ion transport apparatus and combinations thereof.
• the method and apparatus of the present invention are also applicable to a suppressor, and other electrolytic devices such as eluent purifier (US Patent Application 20030127392) or aqueous stream purifier (US Patent Application 20030132163), and the like.
• eluent purifier US Patent Application 20030127392
• aqueous stream purifier US Patent Application 20030132163
• the system is first described with respect to the generation of a base suitable for use as an eluent in the analysis of anions in a chromatographic separator, such as a chromatography column packed with anion exchange resin.
• the generated base typically is an alkali-metal hydroxide, such as sodium or potassium hydroxide, for analysis of anions.
• the eluent generated would be an acid such as methanesulfonic acid.
• one way of electrodialytically generating a hydroxide eluent uses a substantially stationary or non-flowing stream of KOH on one side of an ion exchange barrier.
• An electrode e.g., formed of a metal, e.g. a noble metal, functioning as an anode in electrical communication with the KOH solution, preferably is disposed in the solution.
• the KOH solution is separated from the other side by a cation exchange membrane (CEM) or a stack of CEMs (for mechanical stability in high-pressure application).
• CEM cation exchange membrane
• Aqueous solutions preferably purified water, flows on the other side of the CEM. Under the electric field, K ions move across the membrane, according to the principle illustrated in the ' 129 patent.
• a barrier comprising a wall with an ion exchange bead in a bead seat or a barrier comprising an array of beads replaces the ion exchange membrane, e.g. in the devices of the ' 129 or '976 patents.
• the source of anions or cations can be a flowing stream as set forth in the '204 patent.
• Electrodialytic generation of a hydroxide eluent is performed using a stationary or flowing stream of KOH on one side and an ion exchange barrier with a noble metal electrode, functioning as an anode, disposed therein in electrodialytic eluent generators (EDGs).
• EDGs electrodialytic eluent generators
• the KOH solution is separated from the other side by the cation exchange barrier. Pure water flows into the other side where a negative electrode is disposed. Under the electric field, K + moves across the membrane, the cathode reaction being
• an ion transport barrier which includes a wall with a bead seat and an ion exchange bead sealed in the bead seat.
• the bead is capable of passing ions of one charge, positive or negative, and of substantially blocking bulk liquid flow.
• substantially blocking means blocking all flow except a small amount of liquid leakage. Preferably, essentially all bulk liquid flow is blocked.
• ions of one charge, positive or negative, e.g. K + ion, in an aqueous liquid in a first chamber are transported to an aqueous liquid in a second chamber through a barrier which prevents ion flow but which blocks bulk liquid flow.
• the first chamber serves as an ion source chamber
• the second chamber includes a flowing aqueous solution, typically a flowing purified water stream.
• the barrier is a wall separating the first and second chambers which comprises at least a first ion exchange bead sealed in one or more bead seats.
• the ion exchange bead is in fluid communication with the ion source liquid in the first chamber and with the aqueous liquid in the second eluent generation chamber and is capable of passing positive or negative ions and of blocking bulk liquid flow.
• a first electrode is in electrical communication with the ion source (first) chamber and a second electrode of opposite charge is in electrical communication with the solution in the eluent generation (second) chamber in which the acid or base eluent is generated.
• the second chamber is of an elongate generally tubular configuration, specifically a capillary conduit.
• the ion exchange bead is particularly effective for use in a high pressure system for the second chamber, and one of small dimensions, such as a capillary conduit.
• the bead is preferably of spherical shape. Other shapes are possible provided the bead is scaled in the bead seat.
• the present invention also describes an array of bead configuration.
• an electrodialytic generator according to the present invention which is very effective for use in producing an eluent in a high- pressure system, e.g. greater than about 100 psi, or greater than about 1000 psi, 5000 psi or more.
• This system includes a source of purified aqueous liquid, preferably deionized (DI) water 10, which flows through a conduit, tubing 12, with suitable connector 14 to flow- through eluent generation chamber 16 in cylindrical conduit or tubing 18 connected by suitable connector 20 to an outlet conduit, tubing 22.
• Tubes 24a and 24b define ion source reservoirs 26a and 26b, respectively, terminating at one end with outlets adjacent to chamber 16.
• ion exchange bead 28a and 28b Disposed between chamber 16 and chambers 26a and 26b are ion exchange bead 28a and 28b, respectively, of the same or opposite charge.
• Bead 28a is in fluid communication with chamber 26a and chamber 16
• bead 28b is in fluid communication with chamber 26b and chamber 16.
• the ion exchange beads are capable of passing ions of one charge, positive or negative, and of blocking bulk liquid flow.
• Beads 28a and 28b are sealed in cavities or bead seats 24c and 24d in the form of recesses in the portion of tubes 24a and 24b adjacent to tube 18.
• the combination of the beads and the surrounding interior walls of conduits 24a and 24b are bead seats 24c and 24d forming liquid seal.
• the term "wall” encompasses a wall or wall portion defining a bead seat or seats in which a bead or beads are sealed.
• the wall is sealed at its periphery to the interior of the device to block bulk liquid flow around the wall.
• Other embodiments of walls according to the invention could include walls of any configurations such as a flat or curved sheet-like walls, or the interior wall of a conduit such as a tube.
• the walls are inert, not electrical conductive, and do no swell substantially due to hydration.
• Preferred substrates include substantially non-swellable plastic or non- swellable polymer materials such as polypropylene, polyethylene, PEEK, PTFE and the like.
• the thickness of the substrate material typically is less than 5000 microns ( ⁇ m), preferably less than 1000 microns, and more preferably less than 500 microns.
• the bead seat opening typically are less than 5000 microns in diameter for a round opening and of comparable cross-section for an opening of another shape, preferably less than 1000 microns and more preferably less than 500 microns.
• the bead seat recesses can be of any shape so long as the ion exchange bead is tightly held in the recess without any substantial leaks.
• the bead seat recesses can be machine drilled.
• the bead seat recesses may be formed as a counter-sunk bore, or of semi-spherical shape.
• the wall may be injection molded in the form of a substrate sheet or other configuration, with the required bead seat configuration. In the molded version appropriate details to the hardware may be integrated to ensure that the bead is entrapped in the bead seat recess in a check valve type configuration. Other modes of sealing may be used.
• One way to form the seal is to insert the bead in a dry form in bead seats 24c and 24d in the tubing. Then the bead is wetted to expand and form a tight seal within the tubing, preferably formed of a rigid, electrically non-conducting (e.g. plastic) material such as PEEK. The bead is trapped in the bead seat and exposed to liquids on both sides.
• a rigid, electrically non-conducting (e.g. plastic) material such as PEEK.
• PEEK electrically non-conducting
• Such an assembly functions as a ball-in-seat check valve since flow would ensure a tight seal between the bead and the surface of the tube in which it is seated.
• the dry bead expands in place when contacted with liquid to ensure a tight fit.
• anion exchange resin beads could be put into a shrunken nitrate form and then converted to the hydroxide form to expand and provide a physical seal against the cavity.
• cation exchange resin beads the sodium form may be converted to hydronium form, resulting in an expansion of the beads that can be used to make a seal against the PEEK cavity.
• the resin beads are of a generally spherical form and can be of the type and size used for resin beds used in a variety of applications from chromatography to water purification.
• the beads are cross-linked to a sufficient extent to provide structural strength, e.g. at least 2 %, more preferably at least about 8% and to as high as 50% or more.
• the beads are ion exchange materials. Such materials are well known in the prior art and are typically polymer based for example styrene divinylbenzene based cross-linked resin and the like.
• Another advantage of the present invention over ion exchange membranes is avoiding the influence of such swelling on membrane performance. For example, when suppressor membranes are too dry and are assembled, the swelling forces may result in increasing the device internal back pressure due to the expansion of the membrane. Higher internal pressures in suppressor devices or water purifier devices are not desirable as this can cause these devices to leak. By selectively allowing ion transport through ion exchange beads in specific regions in the wall of the present invention, the above problems of ion exchange membranes are minimized or overcome. [0034] A device built with the single bead or array of bead configuration shows high resiliency under high pressure conditions. In contrast, devices built with conventional ion exchange membranes can leak and show poor pressure resiliency.
• the resin beads of the present invention are preferably slightly smaller than the bead seat holes when the sealing occurs via swelling of the beads.
• the resin bead can be slightly larger than the bead seat recesses. It is also possible to use large resin bead and only expose a small portion of the resin surface via the bead seat. This can be used when the resin is held in place by sealing against the bead seat perimeter, e.g. by the application of heat as described above..
• the resin beads are preferably substantially spherical although other shapes may be used. They are typically less than 5000 microns nominal diameter; preferably less than 1000 microns, and more preferably less than 500 microns for use in some devices such as microdevices, e.g. when seated in a capillary tube.
• the rate of ion transport through the ion exchange bead or beads in a wall can be controlled by the ratio of the exposed surface area of the beads relative to the wall in which the beads are seated.
• the ratio of exposed bead surface area to the surface area of the exposed surrounding wall containing the bead seats be at least 1 :1 , more preferably at least 2:1, and most preferably at least 5:1 to 10:1 or more.
• the ion source 30, e.g., KOH in an aqueous solution flows through the interior of electrically conductive (metal) tubes 32a and 32b disposed in chambers 26a and 26b to direct the KOH solution to outlets in chambers 26a and 26b close to beads 28a and 28b, respectively.
• the KOH solution flows out of tubes 32a, and 32b through outlet tubes 34a and 34b, respectively.
• Tubes 32a and 32b also serve as electrodes of opposite polarity and are connected to a power source, not shown. During operation, an electric current flows between chambers 26a and 26b through chamber 16.
• the ion source is ion exchange medium such as an ion exchange bed in an aqueous solution.
• the second electrode is in communication with the eluent generating chamber, preferably in contact with solution therein.
• FIG. 2 Another embodiment is illustrated in Figure 2 in which the two beads are side by side within the same horizontal plane. Like parts will be designated with like numbers.
• Bead 28a is a cation exchange bead
• bead 28b is an anion exchange bead.
• the water flows into an inlet tube 36 at the top of the device through conduit 38 across conduit 40 and the produced KOH flows up conduit 42 and out conduit 44.
• This embodiment has the advantage that it is easily modified to accommodate multiple resin beads or bead arrays as will be described hereinafter.
• an array of beads is used seated in multiple seats in a wall which can be of a generally flat or curved sheet- like configuration.
• a flat configuration of the array of beads configuration is shown in Figure 3a and 3b and 4a and 4b.
• the exposed surface of one bead is arranged in close proximity to or in contact with other exposed bead surfaces in their respective seats.
• the resulting configuration produces a functional sheet-like (e.g. thin-film) ion exchange surface analogous to an ion exchange membrane as used in prior art ion transport devices.
• Advantages of the bead array configuration over an ion exchange membrane include physical rigidity and strength.
• a single ion exchange bead is in fluid communication with fluid in the chambers on opposite sides of the bead.
• two or more ion exchange beads are stacked in a tandem line extending between fluids in the two chambers.
• a first bead is in fluid communication with a first chamber and a second bead is in fluid communication with a second chamber.
• Intermediate beads can be interposed between the first and second beads.
• the tandem beads contact each other and provide a continuous ion transport path between the first and second chambers.
• the ions are transported from the first chamber to the second chamber through at least one ion exchange bead.
• a reverse electrical bias may be applied in the system of the present invention.
• a potential is applied in the reverse direction of the current normally applied to generate the eluent.
• An eluent generator that can produce nearly pure water when demanded (i.e. water containing less KOH than would be leaking out under no-voltage applied conditions) and also produce high KOH concentrations when demanded can be provided with a bipolar variable voltage power supply which contains at least two electrodes one being held at ground potential and connected to the water side while the second electrode, whose potential can vary continuously from a negative value with respect to the said ground electrode to a positive value with respect to the said ground electrode is deployed on the feed KOH side.
• the potential of the electrode on the KOH side is varied, continuously if desired, from a negative value to a positive value.
• terminal 1 is maintained at ground potential
• terminal 2 can assume any potential from 0 to +15 V with respect to terminal 1
• terminal 3 can assume any potential from 0 to -15 V with respect to terminal 1.
• one of the electrodes is connected to terminal 1.
• the other electrode is connected to either terminal 2 or terminal 3 as selected by an automated relay, which is switched at the appropriate time.
• the bipolar variable voltage power supply of the prior paragraph is a single power supply capable of applying two voltages of opposite polarity to a pair of electrodes so that two different voltages of opposite polarity can be applied in a programmed manner.
• This is referred to as the reverse electrical bias embodiment.
• two independent power supplies can perform this reverse polarity function.
• the term "power supply" refers to both a single power supply and two or more independent power supplies that perform these dual functions.
• the above system has been described with respect to an eluent generator. However, it is applicable to the substitution of the seated ion exchange bead barrier for ion exchange membranes in other ion transport apparatus and method.
• the ion exchange bead is substituted for the ion exchange membrane.
• the reverse electrical bias embodiment may not be applicable to a suppressor.
• the KOH solution illustrated in Figures 1 and 2 herein can comprise the liquid sample stream containing the electrolyte to be suppressed exiting from the chromatographic column 10 in Figure 1 of the '360 patent.
• the solution on the other side of the ion exchange beads 28a and 28b may comprise a regenerant solution (e.g. water for an electrolytic suppressor) which flows on the other side of the ion exchange membrane from the liquid sample stream in the '360 patent.
• a regenerant solution e.g. water for an electrolytic suppressor
• the ion source can be fed to the ion source chambers without flowing through electrode tubes.
• the ion source chamber can be a substantially non-flowing solution, such as illustrated in the large-capacity reservoir of U.S. Patent No. 5,352,360.
• the bead array approach is particularly effective.
• the ion exchange bead approach is applicable to a non-electrolytic ion transport device and method which does not use electrodes. Note that a bead array does not have to be a one dimensional array (1 x n); rather it can be a multidimensional array where mn beads are deployed in a m x n array.
• FIG. 1 The design in Figure 1 is made from a commercial cross fitting and the data are based on this device.
• the through-channels of both arms of a 10-32 cross fitting (P-730, Upchurch) were bored out for V 16 in. o.d. PEEK tubing to just pass through.
• the terminal bore at one end was widened to 0.9 mm (0.035 in.) to a depth of ⁇ 1 mm.
• Ion exchange resin beads (Rexyn 101 H + -type for the cation exchange resin (CER) and Dowex AG -2X8 Cl -form for the anion exchange resin (AER)) were dried in a desiccator and hand-picked to obtain resin beads in the 0.8 -0.85 mm size range.
• CER and AER bead were placed in the respective drilled out cavities in the PEEK tube and wetted with water whereupon they expanded and lodged tightly in the cavity.
• these two bead-bearing tubes were placed opposite each other and fixed in place with 10-32 nuts and ferrules, water inlet and eluent outlet tubes were then similarly connected.
• each bead-bearing tube was cut off essentially flush with the back of the holding nuts and a small segment of Tygon sleeve tubing put over the ends of the Vi 6 in. o.d. PEEK tubes.
• a blunt-ended platinum needle (0.25 mm i.d., 0.45 mm o.d.; 26 ga., 1 in. long, P/N 21126 PT 3, Hamilton Co. Reno, NV) was put in all the way into the PEEK tubing, (almost) touching the bead.
• the exit of the Pt Needle from the Tygon tube was sealed with hot-melt adhesive.
• the Pt- needle functioned both as the electrode and the liquid inlet tube; the liquid outlet was provided by a 0.25 mm. i.d., 0.51 mm o.d. PEEK tube (P/N 1542, Upchurch) breaching the Tygon tube wall, and affixed in place with adhesive.
• the nominal internal volume of this generator without considering the space that the protrusion of the spherical beads may consume, the volume is ⁇ 3.2 ⁇ L.
• a high pressure capillary IC system consisted of a high pressure syringe and a high pressure header valve (P/N 23994 and 26098, Kloehn) connected to a flow-through pressure sensor (SP70 A-3000, www.senso-metrics.com) via 0.25 mm i.d., 1.6 mm o.d. PEEK tubing.
• the stream passes through the high pressure generator, as described above. Unless otherwise stated, in the generator, 100-200 mM KOH was used for feeding both electrode chambers.
• the reservoir was pressurized at 12 psi (the pneumatic line contained a soda lime trap to prevent intrusion Of CO 2 into the liquid) and this was sufficient to establish a flow of ⁇ 500 ⁇ L/min each through both anode and cathode chambers.
• the effluent could in principle be recycled but this was not presently carried out.
• the injection volume was 200 nL.
• a chromatographic flow rate of 3.2 ⁇ L/min was used throughout otherwise stated.
• the generator output proceeded through a first conductivity cell consisting of two 4.5 cm long, 0.25 mm bore, 1.6 mm o.d. stainless steel (SS) tubes joined by a 10-32 PEEK union with the gap between the two SS tubes being ⁇ 1 mm).
• SS stainless steel
• the SS tubes functioned as flow-through electrodes connected to bipolar pulse conductivity detection electronics (CDM-I , Dionex Corp.).
• CDM-I bipolar pulse conductivity detection electronics
• the conductance calibration data were used to translate measured conductance values to KOH concentration. This detector output was thus used to measure the generated KOH concentration.
• a monolithic anion exchanger column (housed in a 0.25 mm i.d. x 0.365 mm o.d. x 260 mm long fused silica capillary) used in this work utilized a sulfonated functionality acrylate cation exchanger as a starting point. This was converted to an anion exchanger by pumping a colloidal solution of anion exchanger nanoparticles (AS 18 latex, Dionex Corp.) until no further retention of the latex was apparent.
• silica capillary columns 50 ⁇ m and 75 ⁇ m in i.d., each 5-m long, were coated with AS-11 anion exchanger latex nanoparticles supplied by Dionex Corp.
• a Kloehn V6 syringe pump www.Kloehn.com
• the anode compartment of the generator was fed with 10-20 mM (10 mM if not otherwise specified) KOH by a peristaltic pump.
• the cathode compartment was fed independently with the same liquid or with pure water. In this case a 20 nL loop volume internal loop sample injector was used.
• the column effluent passed through a tubular Nafion membrane suppressor regenerated by 10 mM H 2 SO 4 ) into a contactless conductivity detector.
• This detector was calibrated to function in a low conductivity range and to thus measure analyte signals.
• two tubular SS segments (0.41 mm i.d. x 0.66 mm o.d. x 15 mm long) were affixed with epoxy adhesive directly on the silica capillary exiting the suppressor, with a 1 mm interelectrode gap.
• the electrodes were coupled to an AD7746 (www.analogdevices.com) capacitance to voltage digital converter evaluation board and then forms a complete contactless conductance detector, in which the measured signal is proportional to the solution conductance in the low conductance domain relevant to this work.
• AD7746 www.analogdevices.com
• FIG. 3a This example illustrates the bead array of Figures 3a and 3b.
• cation exchange resin beads (52) purchased from Rohm & Haas and sold as Amberjet UP 1400 semi conductor grade cation exchange resin, were sized to barely fit the 508 micron hole. The ion exchange resin bead is in the dry form during this step.
• FIG. 4a This example illustrated the bead area of Figures 4a and 4b.
• a thicker version of the polypropylene sheet from Example 3 (0.06" in thickness) was drilled with multiple conduits of 0.02" id from the surface 48a and up to a depth of 0.055". The bottom of the conduit was opened on the 48b surface to a dimension of 0.015" to create a bead seat.
• Dry cation exchange resin from Example 3 was used to pack the conduit, three beads in each conduit.
• the finished product is a thick cation exchange membrane similar to the membrane shown in Example 3. The resin in the bottom layer is held in place against the bead seat and forms a seal.
• Appropriate backing such as a polypropylene screen (not shown) can be placed along the surface 48a to ensure that the resin beads are held in place. Any flow of liquid along the surface 48a will force the cation exchange beads against the surface at 48 b thus forming a high pressure seal as per the present invention.
• An enlarged view of the resin bead seat sealing interface is shown in Figure 4b. This membrane is suitable for assembly in an ASRS suppressor device and replaces the cation exchange membrane.
• Figure 5 shows plots for both current-voltage and applied voltage vs. generated KOH concentration for the resin bead based generator of Figure 1 with 4 M KOH in both CER and AER chambers.
• the applied voltage spans from negative to positive.
• significant current pass only when the polarity is such that the electric field aided induced ion transport is permitted by the respective exchangers.
• This is analogous to the behavior of a semiconductor diode but the current through the device is carried by ionic transport.
• a small negative current is generated under negative applied voltage (KOII feed side negative with respect to water receiving side); this exhibits a much smaller slope than the positive i-V slope when the applied voltage is +ve.
• a bias of approximately -1 V is needed under these specific conditions.
• a major advantage of the resin beads approach is their ability to function as robust ball-in-seat check valves. To assure ample mechanical strength of the exchange bead, we only worked with resin beads with a crosslinking of 8% and higher, it is well known that beads with up to 50% crosslinking have been prepared. The second factor is to assure the seal between the ball and the seat. As long as we picked beads with no observable surface imperfections or cracks as observed under a low magnification microscope, no problems were encountered. The ability to withstand high-backpressure and leakage from the generator chamber out was explored.
• the EDG was connected to a column that generated a backpressure of 1400 psi (the highest rated pressure for the syringe header valve was 1500 psi) at the programmed syringe flow rate of 7 ⁇ L/min.
• the terminal flow in the system was measured with and without the column. During this period the EDG was not operated (i.e., no voltage was applied) and we also measured any leakage of fluid through the capillaries in the electrode chambers over 30 min long periods. There was no observable leakage.

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• 2007
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