Variable flow rate injector

Abstract

A variable flow rate injector provides accurate, precise, and reproducible injection volumes that have low dispersion. The invention is particularly well-suited for HPLC injection volumes <500 nL but can be used to inject larger volumes and in different applications as well. Injections are performed at a first flow rate and separations are performed at a second flow rate. For improved HPLC system performance, the first flow rate is less than the second flow rate. The injector uses a variable flow rate fluid supply that allows rapid switching between flow rates desired for injection and flow rates desired for separations.

1 . (canceled)  
   
   
       2 . An injector system for injecting a sample into a device comprising: 
 (a) a variable flow rate source of a working fluid;    (b) a sample source;    (c) a valve in fluid communication with the sample source and with the working fluid source, wherein the valve has (i) a sample load position, and (ii) a sample inject position, wherein in the sample inject position sample from the sample source can be placed in a sample injection zone for injection by the working fluid into the device; and    (d) a controller in communication with the working fluid source for controlling the flow rate of the working fluid, wherein the working fluid flows at a first flow rate when the working fluid is injecting placed sample into the device and the working fluid flows at a second flow rate after the working fluid injects the sample into the device; 
 wherein the first flow rate is less than the second flow rate.  
   
   
   
       3 . A system of  claim 2  where the device is a microcolumn of a HPLC system.  
   
   
       4 - 12 . (canceled)  
   
   
       13 . The system of  claim 2  wherein the variable flow rate source comprises an electroosmotic flow controller.  
   
   
       14 . The system of  claim 2  wherein the variable flow rate working source comprises an electrokinetic pump.  
   
   
       15 . The system of  claim 2  wherein the variable flow rate working source comprises a variable pressure source.  
   
   
       16 . The system of  claim 2  comprising a plurality of variable flow rate working fluid sources.  
   
   
       17 . The system of  claim 16  further comprising flow detection means for detecting the flow rate of working fluid from each variable flow rate working fluid source, the flow detector means being in communication with the controller; 
 wherein the controller can compare the detected flow against a target flow rate and adjust a respective variable flow rate working fluid source so the respective working fluid flows at about the target flow rate.    
   
   
       18 - 26 . (canceled)  
   
   
       27 . A system for injecting a sample into a device comprising the steps of: 
 (a) means for placing the sample into a remote injection zone;    (b) means for moving at least a portion of the placed sample from the sample injection zone into the device with a working fluid at a first flow rate;    (c) means for introducing the working fluid into the device at a second flow rate, wherein the first flow rate is at least 25% less than the second flow rate; and    (d) a controller for controlling the flow rates.