Helium Conservation Device for a Gas Chromatograph

Abstract

A device for conserving helium gas in a gas chromatograph system is characterized in that during the majority of an analytical separation, helium is used as the carrier gas while an auxiliary non-helium gas is used to pressurize the inlet and provide for septum purge and split vent flow. Prior an injection period, a coaxial helium flow is established at the column entrance wherein the coaxial helium flow is less than the column flow. Following the injection and sample transfer period, a coaxial helium flow is established wherein the flow is greater than the column flow.

We claim: 
     
         1 . A device for a gas chromatograph (GC) system comprising:
 an injector connected to a helium gas source and a non-helium gas source;   wherein the non-helium gas source is configured to pressurize an input end of analytical column and to deliver at least one of a split or purge gas flow; and   a conduit assembly, including,   a conduit surrounding the input end of the analytical column,   a controller, connected to the conduit, having a first mode delivering a flow of helium which is less than the column flow during an injection period to effect a sample transfer to the column and a second mode delivering a flow of helium greater than the column flow following an injection period to prevent the non-helium gas from entering the analytical column.   
     
     
         2 . A device as in  claim 1 , the controller including a pneumatic switch for temporarily switching the non-helium gas source to helium preceding an injection period, and switching back to the non-helium gas source following an injection period. 
     
     
         3 . A device as in  claim 1 , wherein the controller is a secondary injector. 
     
     
         4 . A device as in  claim 1 , the controller including an electronic pressure controller connected to a three-way valve receiving one of an auxiliary gas or helium;
 a secondary valve and calibrated restrictors for delivering two levels of helium flow to the conduit;   a T connector interposes an injector and an analytical column, having a midpoint that connects to the conduit; and   a gas chromatograph detector connects to the output of the analytical column.   
     
     
         5 . The device of  claim 4 , wherein the gas chromatograph detector is a mass spectrometer. 
     
     
         6 . The device of  claim 1 , wherein the injector is a split/splitless (SSL) injector. 
     
     
         7 . The device of  claim 1 , wherein the injector is a programmed temperature vaporization injector (PTV). 
     
     
         8 . The device of  claim 1 , wherein the auxiliary gas is selected from a group consisting of hydrogen, nitrogen, and argon. 
     
     
         9 . The device of  claim 7 , further comprising a heated precolumn interposing the output of the programmable temperature vaporizing injector and the T connector. 
     
     
         10 . The device of  claim 1 , the injector including:
 a removable 2-piece injector base having a threaded stem at a terminal end, the threaded stem including a conduit having an input at an upper end of the threaded stem and an output at a lower end of the threaded stem;   above the removable injector base,
 an injection port liner; 
 a conduit within the injection port liner; 
 an analytical column positioned within the conduit; 
 a ferrule concentrically positioned around the conduit, the 2-piece base threaded together such that the ferrule is compressed and; 
 a grooved gasket interposing the base and injection port to effect fluid communication between the helium gas source and the base. 
   
     
     
         11 . The device as in  claim 10 , wherein the analytical column is encased by the conduit. 
     
     
         12 . The device as in  claim 10 , the grooved gasket including:
 for each face of the gasket including an annular groove;
 a via within the annular grooves. 
   
     
     
         13 . The device as in  claim 10 , further including:
 a first valve in communication with the input end of the conduit;   at least one capillary restrictor connected in series with the first valve; and   the helium gas source in fluid communication with the at least one capillary restrictor, having a first mode directing the helium gas across the input end of the column at a flow rate larger than the flow rate of the column, having a second mode reducing the flow of the helium gas across the input end of the column to a value which is less than the flow of the column to effect a sample transfer to the column.   
     
     
         14 . The device of  claim 10 , wherein the auxiliary gas is selected from a group consisting of hydrogen, nitrogen, and argon.