Membrane based volatile component-removal devices for liquid chromatography

Abstract

In a liquid chromatographic system, removing at least part of a volatile component from the liquid sample stream after separation by flowing it through a volatile component-removal device including a porous wall having a surface coating of a permeable polymer less than 10 μm thick. A liquid chromatographic system suitable for performing the method. Also, a liquid chromatographic system in which volatile component is removed prior to separation across the same type of membrane or across a membrane made of a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole.

1 . A liquid chromatographic method including removal of a volatile component from an aqueous liquid sample stream, said method comprising:
 (a) chromatographically separating analytes in a liquid sample stream including a volatile component, and   (b) removing at least part of a volatile component from the liquid sample stream from step (a) by flowing it through a volatile component-removal device comprising at least one porous wall having a surface coated with a silicone polymer permeable to said volatile component, said coating thickness being less than 10 μm.   
     
     
         2 . The method of  claim 1  further comprising the step of:
 (c) after step (b), detecting said analytes.   
     
     
         3 . The method of  claim 1  in which the volatile component is carbon dioxide. 
     
     
         4 . The method of  claim 1  in which the volatile component-removal in said removal device is at least 90%. 
     
     
         5 . The method of  claim 1  in which the polymer coating comprises a siloxane. 
     
     
         6 . The method of  claim 1  in which the polymer coating is on the exterior of said porous wall in the form of tubing and said liquid sample stream flows through the interior of said tubing. 
     
     
         7 . The method of  claim 1  in which said porous wall is substantially flat. 
     
     
         8 . The method of  claim 1  further comprising providing an other aqueous liquid to said volatile component-removal device on one side of said polymer coated wall, said aqueous liquid sample stream flowing on the other side of said polymer wall, and transporting said volatile component from said flowing liquid sample stream across said polymer coated wall into said other aqueous liquid. 
     
     
         9 . The method of  claim 1  further comprising, after step (a) and prior to step (b), suppressing the liquid sample stream by flowing it through a suppressor, flowing a suppressed liquid stream exiting from said suppressor to a detector, and flowing a second liquid stream exiting said suppressor to serve as said flowing other aqueous liquid stream. 
     
     
         10 . A liquid chromatographic system comprising:
 (a) a liquid chromatographic column having an inlet and an outlet and,   (b) a volatile component-removal device comprising a membrane comprising at least one porous wall having a surface coated with a silicone rubber coating of polymer, said coating having a thickness less than 10 μm, said device defining a liquid sample stream flow channel having an inlet and an outlet, said liquid sample stream flow channel inlet being in fluid communication with said chromatographic column outlet.   
     
     
         11 . The system of  claim 10  further comprising a volatile component-removal compartment on the opposite side of said membrane from the sample stream flow channel. 
     
     
         12 . The system of  claim 10  in which said membrane comprises tubing. 
     
     
         13 . The system of  claim 12  further comprising:
 (c) an aqueous liquid stream source in fluid communication with the outside of said tubing.   
     
     
         14 . The system of  claim 10  in which said silicone rubber is a siloxane. 
     
     
         15 . A liquid chromatographic method including removal of a volatile component from an aqueous liquid sample stream, said method comprising:
 (a) removing at least part of a volatile component from a liquid sample stream containing it by flowing it along one side of a membrane in a removal device, said membrane comprising at least one porous wall having a surface coated with a coating of a gas-permeable polymer, said coating thickness being less than 10 μm, and   (b) after step (a), chromatographically separating analytes in said liquid sample stream.   
     
     
         16 . The method of  claim 15  further comprising the step of:
 (c) detecting said analytes in said liquid sample stream.   
     
     
         17 . The method of  claim 15  further comprising detecting said removed volatile component. 
     
     
         18 . The method of  claim 15  in which said removal device further comprises a sample injection loop, said method further comprising loading the liquid sample stream into said sample injection loop after step (a) and before step (b). 
     
     
         19 . The method of  claim 15  in which the volatile component is carbon dioxide. 
     
     
         20 . The method of  claim 15  in which the volatile component removal is at least 90%. 
     
     
         21 . The method of  claim 15  further comprising providing an other aqueous liquid to said removal device on one side of said membrane, said aqueous liquid sample stream flowing on the other side of said membrane, and transporting said volatile component from said flowing liquid sample stream across said membrane into said other aqueous liquid. 
     
     
         22 . The method of  claim 21  in which said other aqueous liquid is a flowing aqueous liquid stream. 
     
     
         23 . The method of  claim 15  further comprising, after step (b) and prior to step (c), suppressing the liquid sample stream by flowing it through a suppressor and flowing a suppressed liquid stream exiting from said suppressor to a detector, and flowing a second liquid stream exiting said suppressor to serve as said flowing other aqueous liquid stream. 
     
     
         24 . The method of  claim 23  in which said suppressor is a membrane suppressor, comprising a suppressor membrane and said other aqueous liquid stream comprises a regenerant solution flowing on the opposite side of said suppressor membrane and said liquid sample stream. 
     
     
         25 . The method of  claim 15  in which said membrane is in the form of tubing and said liquid sample stream flows through the interior of said tubing. 
     
     
         26 . A liquid chromatographic system comprising:
 (a) a volatile component removal device comprising at least one membrane defining a liquid stream sample flow channel, said device having an inlet and an outlet, said membrane comprising at least one porous wall having a surface coated with a coating of polymer, said coating thickness being less than 10 μm, and   (b) a liquid chromatographic column, said volatile component-removal device outlet being in fluid communication with said chromatographic column.   
     
     
         27 . The system of  claim 26  further comprising:
 (c) a detector in fluid communication with said chromatography column.   
     
     
         28 . The system of  claim 26  in which said volatile component-removal device further comprises a volatile component-removal flow channel on the opposite side of said membrane from said liquid sample stream flow channel. 
     
     
         29 . The system of  claim 27  further comprising:
 (c) a first suppressor disposed between said chromatographic column and said detector.   
     
     
         30 . The system of  claim 29  in which said first suppressor is a membrane suppressor comprising a suppressor membrane, and having a sample liquid stream flow channel, said suppressor having a regenerant flow channel on one side of said suppressor membrane, said liquid sample stream flow channel being on the other side of said suppressor membrane in fluid communication with said volatile component-removal flow channel. 
     
     
         31 . The system of  claim 26  in which said membrane comprises tubing. 
     
     
         32 . The system of  claim 26  in which said membrane comprises a flat wall. 
     
     
         33 . The system of  claim 26  further comprising a second suppressor disposed upstream of said volatile component-removal device. 
     
     
         34 . The system of  claim 26  in which said volatile component-removal device comprises a sample injection loop and valving for directing liquid sample into said sample injection loop. 
     
     
         35 . A liquid chromatographic system comprising:
 (a) a volatile component-removal device comprising at least one volatile component-permeable membrane defining a liquid stream sample flow channel, said device having an inlet and an outlet, said membrane comprising an amorphous copolymer of perfluoro-2,2-dimethyl-1,3-dioxole, and   (b) a liquid chromatographic column, said volatile component-removal device outlet being in fluid communication with said chromatographic column.   
     
     
         36 . The system of  claim 35  in which said volatile component-removal device comprises a sample injection loop and valving for directing liquid sample into said sample injection loop. 
     
     
         37 . The system of  claim 12  in which said tubing membrane is disposed within an external tubular housing. 
     
     
         38 . A liquid chromatographic method including removal of a volatile component from an aqueous liquid sample stream, said method comprising:
 (a) chromatographically separating analytes in a liquid sample stream including a volatile component,   (b) suppressing the liquid sample stream from step (a) by flowing it through a sample stream flow channel separated by a permselective membrane from a regenerant liquid stream flow channel in a electrolytic membrane suppressor device.   (c) removing at least part of a volatile component from the suppressed liquid sample stream from step (b) by flowing it through a first flow channel on one side of a porous wall in a volatile component-removal device   (d) flowing the suppressed liquid stream from the first flow channel in step (c) through a detector; and   (e) flowing regenerant liquid through said regenerant stream flow channel and then through a second flow channel in said volatile component-removal device on the other side of said porous wall.   
     
     
         39 . The method of  claim 38  in which said porous wall has a surface coated with a polymer permeable to said volatile component, said coating thickness being less than 10 μm. 
     
     
         40 . The method of  claim 38  in which the volatile component is carbon dioxide. 
     
     
         41 . The method of  claim 38  in which the polymer coating comprises a silicone rubber. 
     
     
         42 . The method of  claim 38  in which the polymer coating is on the exterior of said porous wall in the form of tubing and said liquid sample stream flows through the interior of said tubing.