Sample injector for liquid chromatography, particularly for high performance liquid chromatography

Abstract

A sample injection method for liquid chromatography is performed with an injection valve having a waste port, two sample loop ports, and two high-pressure ports. One high-pressure port can be connected to a pump and the other high-pressure port can be connected to a chromatography column. A sample loop is connected to one of the sample loop ports on one end and to a pump volume of a sample conveying device on the other end. A section of the sample loop can be separated to facilitate receiving a sample fluid in the sample loop. A control unit controls the injection valve and the sample conveying device. The sample injector allows a sample to be loaded into the sample loop and then pressurized to an operating pressure prior to injecting the sample into the chromatography column. The sample loop may also be isolated from the operating pressure for facilitating depressurization of the loop.

1 . A sample injector configured to load a sample into a sample loop at an essentially ambient pressure and then to increase a pressure in the sample loop to an operating pressure, the sample injector comprising:
 a) an injection valve configured to have a LOAD position, a PRESSURE COMPENSATION position, and an INJECT position, the injection valve comprising
 i) a first sample loop port; and 
 ii) a second sample loop port; 
   b) a sample conveying device comprising
 i) a pump volume and 
 ii) a moveable element configured to be moved in a sealed fashion in the pump volume; 
   c) the sample loop comprising two ends, in which the first sample loop port is connected to one of the two ends of the sample loop and the second sample loop port is connected to the other one of the two ends of the sample loop, in which the sample conveying device is positioned so as to form a part of the sample loop; and   d) a control unit configured to
 i) control a change-over process of the injection valve to one of the LOAD position, the PRESSURE COMPENSATION position, and the INJECT position; 
 ii) calculate a distance for a movement of the movable element within the pump volume from a first position to a second position to increase the pressure in the sample loop from the essentially ambient pressure to the operating pressure based on one or more of a compressibility of the sample in the sample loop, an elasticity of the sample loop, and the operating pressure; and 
 iii) control the sample conveying device to move the movable element within the pump volume by the calculated distance from the first position to the second position in the PRESSURE COMPENSATION position to increase the pressure in the sample loop from the essentially ambient pressure to the operating pressure. 
   
     
     
         2 . The sample injector of  claim 1 , in which the control unit is further configured to
 iv) control the sample conveying device to move the movable element within the pump volume by the calculated distance from the second position to the first position in the PRESSURE COMPENSATION position to decrease the pressure in the sample loop to the essentially ambient pressure.   
     
     
         3 . The sample injector of  claim 1 , wherein at the PRESSURE COMPENSATION position, the first sample loop port and the second sample loop port of the injection valve are closed so as to facilitate pressurization of the sample loop. 
     
     
         4 . The sample injector of  claim 1 , in which the injection valve comprises a rotor and a stator. 
     
     
         5 . The sample injector of  claim 1  further comprising a drive device connected to the movable element and configured to move the movable element in the pump volume. 
     
     
         6 . The sample injector of  claim 1 , in which the moveable element comprises a plunger. 
     
     
         7 . The sample injector of  claim 1 , in which the sample loop includes a first connecting piece and a second connecting piece, in which the first connecting piece is connected to the first sample loop port of the injection valve and to the sample conveying device, in which the second connecting piece is connected to the second sample loop port of the injection valve and to the sample conveying device, in which the second connecting piece includes an intake segment and a feed segment, in which the intake segment and the feed segment are configured to be separated. 
     
     
         8 . The sample injector of  claim 1 , wherein at the LOAD position, the sample conveying device is configured to load the sample in the sample loop. 
     
     
         9 . The sample injector of  claim 1 , wherein at the INJECT position, the injection valve is configured to inject the sample in the sample loop into a liquid chromatography column. 
     
     
         10 . A liquid chromatography system comprising
 A) a high-pressure pump;   B) a liquid chromatography column;   C) a sample injector configured to load a sample into a sample loop at an essentially ambient pressure and then to increase a pressure in the sample loop to an operating pressure, the sample injector comprising:
 a) an injection valve configured to have a LOAD position, a PRESSURE COMPENSATION position, and an INJECT position, the injection valve comprising
 i) a first sample loop port; 
 ii) a second sample loop port; 
 iii) a first high pressure port connected to the high-pressure pump; and 
 iv) a second high pressure port connected to the liquid chromatography column; 
 
 b) a sample conveying device comprising
 i) a pump volume and 
 ii) a moveable element configured to be moved in a sealed fashion in the pump volume; 
 
 c) the sample loop comprising two ends, in which the first sample loop port is connected to one of the two ends of the sample loop and the second sample loop port is connected to the other one of the two ends of the sample loop, in which the sample conveying device is positioned so as to form a part of the sample loop; and 
 d) a control unit configured to
 i) control a change-over process of the injection valve to one of the LOAD position, the PRESSURE COMPENSATION position, and the INJECT position; 
 ii) calculate a distance for a movement of the movable element within the pump volume from a first position to a second position to increase the pressure in the sample loop from the essentially ambient pressure to the operating pressure based on one or more of a compressibility of the sample in the sample loop, an elasticity of the sample loop, and the operating pressure; and 
 iii) control the sample conveying device to move the movable element within the pump volume by the calculated distance from the first position to the second position in the PRESSURE COMPENSATION position to increase the pressure in the sample loop from the essentially ambient pressure to the operating pressure. 
 
   
     
     
         11 . The liquid chromatography system of  claim 10 , in which the control unit is further configured to
 iv) control the sample conveying device to move the movable element within the pump volume by the calculated distance from the second position to the first position in the PRESSURE COMPENSATION position to decrease the pressure in the sample loop to the essentially ambient pressure.   
     
     
         12 . The liquid chromatography system of  claim 10 , wherein at the PRESSURE COMPENSATION position, the first sample loop port and the second sample loop port of the injection valve are closed so as to facilitate pressurization of the sample loop. 
     
     
         13 . The liquid chromatography system of  claim 10 , in which the injection valve comprises a rotor and a stator. 
     
     
         14 . The liquid chromatography system of  claim 10  further comprising a drive device connected to the movable element and configured to move the movable element in the pump volume. 
     
     
         15 . The liquid chromatography system of  claim 10 , in which the moveable element comprises a plunger. 
     
     
         16 . The liquid chromatography system of  claim 10 , in which the sample loop includes a first connecting piece and a second connecting piece, in which the first connecting piece is connected to the first sample loop port of the injection valve and to the sample conveying device, in which the second connecting piece is connected to the second sample loop port of the injection valve and to the sample conveying device, in which the second connecting piece includes an intake segment and a feed segment, in which the intake segment and the feed segment are configured to be separated. 
     
     
         17 . The liquid chromatography system of  claim 10 , wherein at the LOAD position, the sample conveying device is configured to load the sample in the sample loop. 
     
     
         18 . The liquid chromatography system of  claim 10 , wherein at the INJECT position, the injection valve is configured to inject the sample in the sample loop into the liquid chromatography column.