Ion chromatography systems with flow-delay eluent recycle

Abstract

A chromatographic method including chromatographically separating sample ionic species in an eluent stream, detecting the separated sample ionic species, catalytically combining hydrogen and oxygen gases or catalytically decomposing hydrogen peroxide in a catalytic gas elimination chamber, and recycling the effluent stream from the chamber to the chromatography separation column. The residence time between the detector and the chamber is at least about one minute. Also, flowing the recycle sequentially through two detector effluent flow channels of an electrolytic membrane suppressor. Also, applying heat or UV energy between the detector and the chamber. Also, detecting bubbles after the chamber. Also, a Platinum group metal catalyst and ion exchange medium in the chamber. Apparatus for performing the methods.

1 . A chromatographic method comprising the steps of:
 (a) injecting sample ionic species into an aqueous eluent stream from an eluent source,   (b) chromatographically separating said sample ionic species in said eluent stream by flowing the same through chromatographic separation medium to exit as a chromatography effluent,   (c) flowing said chromatography effluent through a detector to detect said separated sample ionic species in said chromatography effluent to exit as a detector effluent stream,   (d) catalytically combining hydrogen and oxygen gases or catalytically decomposing hydrogen peroxide, or both, in said detector effluent stream by flowing it through a catalytic gas elimination chamber, to form water and reduce the gas content of the eluent effluent stream exiting said gas elimination chamber, and   (e) recycling said catalytic gas elimination chamber effluent stream from said catalytic gas elimination chamber to said chromatography separation column, the residence time for flow of said detector effluent stream between said detector and said catalytic gas elimination chamber being at least about one minute to facilitate decomposition of unstable oxidative compounds.   
   
   
       2 . The method of  claim 1  further comprising flowing said detector effluent stream through a delay conduit downstream from said detector and upstream from said catalytic gas elimination chamber. 
   
   
       3 . The method of  claim 1  in which said at least one minute residence time occurs in a delay chamber adjacent to said catalytic gas elimination chamber. 
   
   
       4 . The method of  claim 1  further comprising:
 (f) electrolytically forming said hydrogen and oxygen gases in said eluent stream.   
   
   
       5 . The method of  claim 1  further comprising flowing said catalytic gas elimination chamber effluent through an eluent purification column. 
   
   
       6 . The method of  claim 2  in which said delay conduit comprises a delay housing and said detector effluent stream flows through said delay housing in a tortuous path. 
   
   
       7 . The method of  claim 2  in which said delay conduit comprises a flow-through coil. 
   
   
       8 . The method of  claim 2  in which said delay conduit comprises a delay housing and a plurality of tubes, each tube being in parallel fluid communication with said gas elimination chamber effluent. 
   
   
       9 . The method of  claim 8  in which said delay conduit include a delay housing having a cross-sectional area transverse to fluid flow at least 3 times the cross-sectional area of said recycle conduit. 
   
   
       10 . A chromatographic method comprising:
 (a) injecting sample ionic species into an aqueous eluent stream from an eluent source,   (b) chromatographically separating sample ionic species in an aqueous liquid eluent stream flowing through a chromatography separation medium, to form a chromatography effluent,   (c) suppressing the chromatography effluent from step (b) by flowing it through a chromatography effluent flow channel in an electrolytic membrane suppressor to exit as a suppressor effluent stream,   (d) flowing said suppressor effluent stream past a flow-through detector to exit as a detector effluent stream,   (e) flowing the detector effluent stream from step (d) through a first detector effluent flow channel in said membrane suppressor on the opposite side of a first ion exchange membrane from said chromatography effluent flow channel, said detector effluent exiting said first detector effluent flow channel as a recycle stream,   (f) flowing said recycle stream through a catalytic gas elimination chamber to catalytically combine hydrogen and oxygen gas, or catalytically decomposing hydrogen peroxide, or both, to form water thereby reducing the gas content in said recycle stream, and   (g) flowing said recycle stream from said catalytic gas elimination chamber to said chromatography separation medium, the time for flow of said detector effluent from said first detector effluent flow channel to said catalytic gas elimination chamber being at least 0.5 minute to facilitate decomposition of unstable oxidation compounds.   
   
   
       11 . The method of  claim 10  further comprising, between steps (e) and (f), flowing said recycle stream from said first detector effluent flow channel through flow-through ion exchange medium in an electrolytic eluent generator separated from an eluent generator chamber by a charged generator barrier and applying a current across said generator ion exchange medium to electrolytically generate the same, electrolytically regenerating said suppressor ion exchange medium, and flowing said generated eluent to said chromatography separation medium. 
   
   
       12 . A chromatographic method comprising:
 (a) injecting sample ionic species into an aqueous eluent stream from an eluent source,   (b) chromatographically separating sample ionic species in an aqueous liquid eluent stream flowing through a chromatography separation medium, to form a chromatography effluent,   (c) suppressing the chromatography effluent from step (b) by flowing it through a chromatography effluent flow channel in an electrolytic membrane suppressor to exit as a suppressor effluent stream,   (d) flowing said suppressor effluent stream past a flow-through detector to exit as a detector effluent stream,   (e) flowing the detector effluent stream from step (d) through a first detector effluent flow channel in said membrane suppressor on the opposite side of a first ion exchange membrane from said chromatography effluent flow channel, and then through a second detector effluent flow channel on the opposite side of a second ion exchange membrane in said membrane suppressor from said chromatographic effluent flow channel, said detector effluent exiting said second detector effluent flow channel as a recycle stream,   (f) flowing said recycle stream through a catalytic gas elimination chamber to catalytically combine hydrogen and oxygen gas, or catalytically decomposing hydrogen peroxide, or both, to form water thereby reducing the gas content in said recycle stream, and   (g) flowing said recycle stream from said catalytic gas elimination chamber to said chromatography separation medium.   
   
   
       13 . A chromatographic method comprising the steps of:
 (a) injecting sample ionic species into an aqueous eluent stream,   (b) chromatographically separating said sample ionic species in said eluent stream by flowing the same through chromatographic separation medium,   (c) detecting said separated sample ionic species in said eluent stream effluent from said chromatographic medium,   (d) catalytically combining hydrogen and oxygen gases or catalytically decomposing hydrogen peroxide, or both, in said eluent stream in a catalytic gas elimination chamber, to form water and reduce the gas content in an eluent stream, in an effluent stream flowing from said catalytic gas elimination chamber, and   (e) detecting bubbles in said catalytic gas elimination chamber effluent stream.   
   
   
       14 . A chromatographic method comprising the steps of:
 (a) injecting sample ionic species into an aqueous eluent stream,   (b) chromatographically separating said sample ionic species in said eluent stream by flowing the same through chromatographic separation medium,   (c) detecting said separated sample ionic species in said eluent stream effluent from said chromatographic medium,   (d) catalytically combining hydrogen and oxygen gases or catalytically decomposing hydrogen peroxide, or both, in said eluent stream in a catalytic gas elimination chamber, to form water and reduce the gas content in an eluent stream, effluent exiting from said catalytic gas elimination chamber, and   (e) between steps (c) and (d), applying energy to said gas elimination effluent to decompose at least a portion of any unstable oxidative compounds therein.   
   
   
       15 . The method of  claim 14  wherein said energy comprises heat. 
   
   
       16 . The method of  claim 14  wherein said energy comprises UV light. 
   
   
       17 . A catalytic gas and ionic species removal device comprising a liquid flow-through housing, a platinum group metal catalyst for catalytically combining hydrogen and oxygen gases, or for catalytically decomposing hydrogen peroxide, or both, disposed in said housing, and flow-through ion exchange medium disposed in said housing. 
   
   
       18 . The device of  claim 17  in which said platinum group metal is selected from the group consisting of platinum, palladium, or a mixture thereof. 
   
   
       19 . The device of  claim 17  in which said platinum group metal is palladium. 
   
   
       20 . The device of  claim 17  in which said catalyst comprises a mixture of platinum and palladium. 
   
   
       21 . The device of  claim 17  in which said ion exchange medium comprises a bed of ion exchange packing. 
   
   
       22 . The device of  claim 17  in which said ion exchange medium comprises an ion exchange monolith. 
   
   
       23 . The device of  claim 17  in which said platinum group metal is irreversibly bound as a coating to the surface of said ion exchange medium. 
   
   
       24 . The device of  claim 23  in which said coating is bound electrostatically to said ion exchange medium. 
   
   
       25 . The device of  claim 23  in which said coated ion exchange medium has excess ion exchange capacity for ion exchange with ions in a flowing liquid stream. 
   
   
       26 . The device of  claim 17  in combination with a chromatography system comprising chromatography separation medium, a detector downstream of and in fluid communication with said chromatography separation medium, a fluid conduit between said detector and said chromatography medium, said device being in fluid communication with said conduit. 
   
   
       27 . A method of catalytically combining hydrogen and oxygen gases, or for catalytically decomposing hydrogen peroxide, or both, and of removing analyte ions, counter-ions, or both, in a flowing liquid sample stream, said method comprising combining hydrogen and oxygen gases or catalytically decomposing hydrogen peroxide in a liquid sample stream containing ions by flowing said liquid sample stream through a flow-through catalytic device containing a platinum group metal catalyst capable of catalyzing said combining or decomposing, and removing said ions from said liquid sample stream in said flow-through device by contact with flow-through ion exchange medium disposed in said device. 
   
   
       28 . The method of  claim 27  wherein said platinum group metal is selected from the group consisting of platinum, palladium, or a mixture thereof. 
   
   
       29 . The method of  claim 27  wherein said catalyst comprises a mixture of platinum and palladium. 
   
   
       30 . The method of  claim 27  wherein said ion exchange medium comprises a bed of ion exchange packing. 
   
   
       31 . The method of  claim 27  wherein said ion exchange medium comprises an ion exchange monolith. 
   
   
       32 . The method of  claim 27  wherein said platinum group metal is irreversibly bound as a coating to the surface of said ion exchange medium. 
   
   
       33 . The method of  claim 32  wherein said coating is bound electrostatically to said ion exchange medium. 
   
   
       34 . The method of  claim 27  wherein said coated ion exchange medium has excess ion exchange capacity for ion exchange with ions in a flowing liquid stream. 
   
   
       35 . The method of  claim 27  performed as a step in a chromatographic method, said method comprising injecting sample ionic species into an aqueous eluent stream, chromatographically separating said sample ionic species in said eluent stream by flowing the same through chromatographic separation medium, and detecting said separated sample ionic species, wherein catalysis by said catalytic device is performed in fluid communication with said eluent stream. 
   
   
       36 . A chromatographic method comprising the steps of:
 (a) injecting sample ionic species into an aqueous stream,   (b) chromatographically separating said sample ionic species in said aqueous stream by flowing the same through chromatographic separation medium while applying an electric field across said separation medium, to exit as a chromatography effluent,   (c) flowing said chromatography effluent through a detector to detect said separated sample ionic species in said chromatography effluent to exit as a detector effluent stream,   (d) catalytically combining hydrogen and oxygen gases or catalytically decomposing hydrogen peroxide, or both, in said detector effluent stream by flowing it through a catalytic gas elimination chamber, to form water and reduce the gas content of the eluent effluent stream exiting said gas elimination chamber, and   (e) recycling said catalytic gas elimination chamber effluent stream from said catalytic gas elimination chamber to said chromatography separation column.   
   
   
       37 . A chromatography apparatus comprising:
 (a) a chromatography column including chromatographic separation medium disposed in the column lumen,   (b) spaced electrodes in electrical communication with said separation medium and disposed to pass an electric current through said separation medium,   (c) a detector,   (d) a conduit for an aqueous liquid stream providing fluid communication between said detector and said chromatographic separation medium, and   (e) a catalytic gas elimination chamber in fluid communication with said conduit and including a catalyst for combining hydrogen and oxygen gases, or for catalytically decomposing hydrogen peroxide, or both, in said eluent stream to form water and reduce the gas content in said eluent stream.