Current efficient electrolytic device and method
A sandwich suppressor in an ion chromatography system in which loosely packed ion exchange resin of low density is disposed in the central sample stream flow channel. Also, a method of using the suppressor is described.
1. Apparatus for treating an aqueous stream, said apparatus comprising
a first ion exchange membrane having exchangeable ions of a first charge and capable of allowing ions of said first charge to pass through said first ion exchange membrane,
an aqueous stream flow channel having an inlet and an outlet,
an ion receiving flow channel adjacent to said aqueous stream flow channel and separated therefrom by said first ion exchange membrane,
stationary flow-through ion exchange packing of a same charge as said first ion exchange membrane disposed in said ion receiving flow channel,
a packed bed of ion exchange particles disposed in said aqueous stream flow channel and extending at least partially between said aqueous stream flow channel inlet and outlet,
a portion of said packed bed being packed at a density between about 1 gram of packed dry particles per cubic centimeter (cc) of said aqueous stream flow channel and less than 2 grams of said packed dry particles per cubic centimeter (cc) of said aqueous stream flow channel,
said packed bed portion extending from said aqueous stream flow channel outlet upstream to at least 30% of a distance between said aqueous stream flow channel inlet and outlet, and
first and second electrodes being in electrical communication with said aqueous stream flow channel and said ion receiving flow channel, respectively, in which a current efficiency of said apparatus when used as a suppressor is at least 75%.
2. The apparatus of claim 1 in which said aqueous stream is a sample stream including analyte ions and matrix ions of opposite charge to said analyte ions, said aqueous stream flow channel comprising an aqueous sample stream flow channel.
3. The apparatus of claim 2 in which said aqueous sample stream flow channel has an upstream portion, in which said sample stream contains matrix ions and an adjacent downstream portion in which said matrix ions have been suppressed.
4. The apparatus of claim 1 in which an ion exchange capacity of said ion exchange particles is at least 0.3 meqv/mL.
5. The apparatus of claim 1 in which said ion exchange particles have a size range of 1 to 200 μm.
6. The apparatus of claim 1 in which an electrical conductivity between said first and second ion exchange membranes through said ion exchange particles in said bed is discontinuous at said aqueous stream flow channel outlet.
7. Apparatus for treating an aqueous stream, said apparatus comprising
a first ion exchange membrane having exchangeable ions of a first charge and capable of allowing ions of said first charge to pass through said first ion exchange membrane,
an aqueous stream flow channel having an inlet and an outlet,
an ion receiving flow channel adjacent to said aqueous stream flow channel and separated therefrom by said first ion exchange membrane,
a second ion exchange membrane of a same type as said first ion exchange membrane and disposed adjacent a side of said aqueous stream flow channel opposite from said first ion exchange membrane,
an ion source flow channel separated from said aqueous stream flow channel by said second ion exchange membrane,
stationary flow-through ion exchange packing of a same charge as said first ion exchange membrane disposed in said ion receiving flow channel,
a packed bed of ion exchange particles disposed in said aqueous stream flow channel and extending at least partially between said aqueous stream flow channel inlet and outlet,
a portion of said packed bed being packed at a density between about 1 gram of packed dry particles per cubic centimeter (cc) of said aqueous stream flow channel and less than 2 grams of said packed dry particles per cubic centimeter (cc) of said aqueous stream flow channel,
said packed bed portion extending from said aqueous stream flow channel outlet upstream to at least 30% of a distance between said aqueous stream flow channel inlet and outlet, and
first and second electrodes being in electrical communication with said aqueous stream flow channel and said ion receiving flow channel, respectively, in which a current efficiency of said apparatus when used as a suppressor is at least 75%.
8. The apparatus of claim 7 in which a static ion exchange capacity of said first and second ion exchange membranes and said packed bed for said aqueous stream flow channel is at least 3 meqv/mL of an aqueous stream flow channel volume.
9. The apparatus of claim 7 in which said current efficiency of said apparatus when used as a suppressor is at least 90%.
10. A method for treating an aqueous stream including analyte ions of one charge and matrix ions of opposite charge to said analyte ions using an apparatus for treating said aqueous stream including said analyte ions and said matrix ions of opposite charge to said analyte ions, said apparatus comprising
a first ion exchange membrane having exchangeable ions of a first charge and capable of allowing ions of said first ion exchange membrane to pass through said first ion exchange membrane, in which the first charge is of a same charge as said matrix ions,
an aqueous stream flow channel having an inlet and an outlet,
an ion receiving flow channel adjacent to said aqueous stream flow channel and separated therefrom by said first ion exchange membrane,
stationary flow-through ion exchange packing of a same charge as said first ion exchange membrane disposed in said ion receiving flow channel,
a packed bed of ion exchange particles disposed in said aqueous stream flow channel and extending at least partially between said aqueous stream flow channel inlet and outlet,
a portion of said packed bed being packed at a density between about 1 gram of packed dry particles per cubic centimeter (cc) of said aqueous stream flow channel and less than 2 grams of said packed dry particles per cubic centimeter (cc) of said aqueous stream flow channel,
said packed bed portion extending from said aqueous stream flow channel outlet upstream to at least 30% of a distance between said aqueous stream flow channel inlet and outlet, and
first and second electrodes being in electrical communication with said aqueous stream flow channel and said ion receiving flow channel, respectively, in which a current efficiency of said apparatus when used as a suppressor is at least 75%, said method comprising
flowing said aqueous stream through said aqueous stream flow channel;
simultaneously flowing an ion receiving stream through said ion receiving flow channel;
suppressing said matrix ions; and
regenerating said first ion exchange membrane, said aqueous stream flow channel having an upstream portion containing said matrix ions and an adjacent downstream portion in which said matrix ions have been suppressed.
11. The apparatus of claim 1 in which said current efficiency of said apparatus when used as a suppressor is at least 90%.
12. The method of claim 10 in which said current efficiency of said apparatus when used as a suppressor is at least 90%.
13. The method of claim 10 in which a current is passed between said first and second electrodes.
14. The method of claim 13 in which said current is passed during suppression and regeneration.
15. The method of claim 13 in which said current is passed during regeneration of said first ion exchange membrane but not during suppression of said matrix ions.
16. The method of claim 10 in which said apparatus further comprises a second ion exchange membrane of a same type as said first ion exchange membrane adjacent an opposite side of said aqueous stream flow channel from said first ion exchange membrane and an ion source flow channel separated from said aqueous stream flow channel by said second ion exchange membrane.
17. The method of claim 16 in which a static ion exchange capacity of said first and second ion exchange membranes and said packed bed for said aqueous stream flow channel is at least 3 meqv/mL of an aqueous stream flow channel volume.
18. The method of claim 10 in which an ion exchange capacity of said ion exchange particles is at least 0.3 meqv/mL.
19. The method of claim 10 in which said ion exchange particles have a size range of 1 to 200 μm.
20. The method of claim 10 in which an electrical current between said first and second ion exchange membranes through said ion exchange particles in said bed at said aqueous stream flow channel outlet is discontinuous.