Sample injector with metering device balancing pressure differences in an intermediate valve state

Abstract

A sample injector for use in a fluid separation system for separating compounds of a fluidic sample in a mobile phase, the sample injector comprising a switchable valve, a sample loop in fluid communication with the valve and configured for receiving the fluidic sample, a metering device in fluid communication with the sample loop and configured for introducing a metered amount of the fluidic sample on the sample loop, and a control unit configured for controlling switching of the valve to transfer the sample loop between a low pressure state and a high pressure state via an intermediate state and for controlling the metering device during the intermediate state to at least partially equilibrate a pressure difference in the sample loop between the low pressure state and the high pressure state.

1 . A method of operating a liquid chromatography system, the liquid chromatography system comprising a liquid chromatography column and an injection valve, the method comprising:
 isolating a sample loop of the liquid chromatography system from a high-pressure fluidic path in fluid communication with the liquid chromatography column, wherein the high-pressure fluidic path is at a pump pressure, the sample loop is in fluid communication with the injection valve, the sample loop comprises a sample conveying device for loading a sample on the sample loop, isolating the sample loop comprises using a motor and encoder to place the injection valve in a PRESSURE COMPENSATION position, and a volume of the sample conveying device is defined by a cavity in which a movable element is slidably mounted;   empirically calculating a distance for a movement of the movable element within the cavity from a first position to a second position to increase a pressure in the sample loop from an essentially ambient pressure to the pump pressure based on one or more of a compressibility of a fluid in the sample loop, an elasticity of the sample loop, and the pump pressure; and   while the sample loop is isolated from the high-pressure fluidic path, decreasing the volume of the sample conveying device to increase the pressure in the sample loop from the essentially ambient pressure to essentially correspond to the pump pressure of the high-pressure fluidic path,   wherein decreasing the volume includes sliding the movable element within the cavity by the empirically calculated distance from the first position to the second position.   
     
     
         2 . The method of  claim 1 , wherein at the PRESSURE COMPENSATION position,
 (i) first and second sample loop ports of the injection valve are closed so as to facilitate a pressurization of the sample loop, and   (ii) first and second high-pressure ports of the injection valve are connected so as to operatively connect a high-pressure pump in fluid communication with the high-pressure fluidic path to the liquid chromatography column.   
     
     
         3 . The method of  claim 1 , wherein placing the injection valve in the PRESSURE COMPENSATION position includes rotating a rotor of the injection valve with respect to a stator of the injection valve. 
     
     
         4 . The method of  claim 1  further comprising:
 using the motor and encoder to operate the injection valve to connect the sample loop to the high-pressure fluidic path such that the pump pressure from a high-pressure pump of the liquid chromatography system is applied to the sample loop, and a sample in the sample loop flows from the sample loop into the high-pressure fluidic path and to the chromatography column. 
 
     
     
         5 . The method of  claim 4  further comprising:
 after operating the injection valve to connect the sample loop, introducing the sample into the chromatography column; 
 isolating the sample loop from the high-pressure fluidic path by placing the injection valve back in the pressure compensation position; and 
 increasing the volume of the sample conveying device to reduce the pressure in the sample loop from the pump pressure of the liquid chromatography column to the essentially ambient pressure. 
 
     
     
         6 . The method of  claim 1 , in which the moveable element includes a plunger. 
     
     
         7 . The method of  claim 2 , 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 . A method of injecting a sample in a liquid chromatography system, the method comprising:
 using a motor and encoder to isolate a sample loop of the liquid chromatography system from a high-pressure fluidic path of the liquid chromatography system, the high-pressure fluidic path at a pump pressure in fluid communication with a liquid chromatography column of the liquid chromatography system, wherein the high-pressure fluidic path is at a pump pressure, wherein the sample loop comprises a sample conveying device for loading a sample on the sample loop, wherein a volume of the sample conveying device is defined by a cavity in which a movable element is slidably mounted;   empirically calculating a distance for a movement of the movable element within the cavity from a first position to a second position to increase a pressure in the sample loop from an essentially ambient pressure to the pump pressure based on one or more of a compressibility of a fluid in the sample loop, an elasticity of the sample loop, and the pump pressure;   placing the sample in the sample loop;   with the sample placed in the sample loop and with the sample loop remaining isolated from the high-pressure fluidic path, decreasing the volume of the sample conveying device to increase the pressure in the sample loop from the essentially ambient pressure to essentially correspond to the pump pressure of the high-pressure fluidic path, wherein the movable element within the cavity is moved by the empirically calculated distance from the first position to the second position; and   using a motor and encoder to connect the sample loop to the high-pressure fluidic path so that the pump pressure from a high-pressure pump is applied to the sample loop to cause the sample in the sample loop to flow from the sample loop through a portion of the high-pressure fluidic path to the chromatography column.   
     
     
         9 . The method of  claim 8  further including:
 isolating the sample loop from the high-pressure fluidic path of the liquid chromatography system after the sample has flowed into the high-pressure fluidic path; and 
 (b) increasing the volume of the sample conveying device to reduce the pressure in the sample loop to the essentially ambient pressure. 
 
     
     
         10 . The method of  claim 8  wherein isolating the sample loop from the high-pressure loop includes placing an injection valve having a motor and encoder in a PRESSURE COMPENSATION position in which
 first and second sample loop ports of the injection valve are closed so as to facilitate pressurization of the sample loop, and 
 first and second high-pressure ports of the injection valve are connected so as to operatively connect the high-pressure pump to the liquid chromatography column. 
 
     
     
         11 . The method of  claim 10  wherein placing the injection valve in the PRESSURE COMPENSATION position includes using the motor to rotate a rotor of the injection valve with respect to a stator of the injection valve. 
     
     
         12 . The method 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. 
     
     
         13 . The method of  claim 8  wherein the movable element is connected to a drive device which is operable to move the movable element within the cavity, and the method further comprises: measuring a force exerted upon the movable element by the drive device. 
     
     
         14 . The method of  claim 8 , in which the moveable element includes a plunger. 
     
     
         15 . A method of operating a liquid chromatography system, the liquid chromatography system comprising a liquid chromatography column and an injection valve, the method comprising:
 isolating a sample loop of the liquid chromatography system from a high-pressure fluidic path in fluid communication with the liquid chromatography column, wherein the high-pressure fluidic path is at a pump pressure, wherein the sample loop is in fluid communication with the injection valve and the sample loop comprises a sample conveying device for loading a sample on the sample loop, and isolating the sample loop comprises using a motor and encoder to place the injection valve in a PRESSURE COMPENSATION position, wherein the sample conveying device comprises a syringe and a movable element in the syringe;   empirically calculating a distance for a movement of the movable element within the syringe from a first position to a second position to increase a pressure in the sample loop from an essentially ambient pressure to the pump pressure based on one or more of a compressibility of a fluid in the sample loop, an elasticity of the sample loop, and the pump pressure; and   while the sample loop is isolated from the high-pressure fluidic path, sliding the movable element within the syringe by the empirically calculated distance from the first position to the second position to increase the pressure in the sample loop from the essentially ambient pressure to essentially correspond to the pump pressure of the high-pressure fluidic path.   
     
     
         16 . The method of  claim 15 , wherein at the PRESSURE COMPENSATION position,
 (i) first and second sample loop ports of the injection valve are closed so as to facilitate a pressurization of the sample loop, and   (ii) first and second high-pressure ports of the injection valve are connected so as to operatively connect a high-pressure pump in fluid communication with the high-pressure fluidic path to the liquid chromatography column.   
     
     
         17 . The method of  claim 16 , in which the sample loop includes a first connecting piece and a second connecting piece, m 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. 
     
     
         18 . The method of  claim 15 , wherein placing the injection valve in the PRESSURE COMPENSATION position includes using the motor to rotate a rotor of the injection valve with respect to a stator of the injection valve. 
     
     
         19 . The method of  claim 15  further comprising:
 operating the injection valve to connect the sample loop to the high-pressure fluidic path such that the pump pressure from a high-pressure pump of the liquid chromatography system is applied to the sample loop, and a sample in the sample loop flows from the sample loop into the high-pressure fluidic path and to the chromatography column. 
 
     
     
         20 . The method of  claim 19  further comprising:
 after operating the injection valve to connect the sample loop, introducing the sample into the chromatography column; 
 isolating the sample loop from the high-pressure fluidic path by using the motor and encoder to place the injection valve back in the pressure compensation position; and 
 sliding the movable element within the syringe from the second position to the first position to decrease the pressure in the sample loop to the essentially ambient pressure. 
 
     
     
         21 . The method of  claim 15 , in which the moveable element includes a plunger. 
     
     
         22 . A method of operating a liquid chromatography system, the liquid chromatography system comprising a liquid chromatography column and an injection valve, the method comprising:
 using a valve to isolate a sample loop of the liquid chromatography system from a high-pressure fluidic path that is in fluid communication with the liquid chromatography column,   maintaining the high-pressure fluidic path at a pump pressure with a high pressure pump, wherein the sample loop is in fluid communication with the injection valve and the sample loop comprises a metering device configured for loading a sample on the sample loop, and isolating the sample loop comprises using a motor and encoder to place the injection valve in a PRESSURE COMPENSATION position, wherein an operative volume of the metering device is defined by a chamber in which a piston is reciprocatingly mounted;   determining a movement amount of the metering piston within the chamber from a first position to a second position to increase a pressure in the sample loop from an essentially atmospheric pressure to the pump pressure, based on the pump pressure; and   while the sample loop is isolated from the high-pressure fluidic path and the high pressure pump, decreasing the operative volume of the metering device to increase the pressure in the sample loop from the essentially atmospheric pressure to essentially correspond to the higher pressure pump pressure of the high-pressure fluidic path;   wherein decreasing the operative volume includes forwarding the piston within the chamber by the determined movement amount from the first position to the second position;   wherein the metering device and the sample loop are in fluid communication in each position of the injection valve.   
     
     
         23 . A method of injecting a sample in a liquid chromatography system, the method comprising:
 using a valve comprising a motor and encoder to isolate a sample loop of the liquid chromatography system from a high-pressure fluidic path of the liquid chromatography system that is in fluid communication with a liquid chromatography column of the liquid chromatography system,   maintaining the high-pressure fluidic path [[is ]]at a pump pressure with a high pressure pump, wherein the sample loop comprises a metering device configured for loading a sample on the sample loop, wherein an operative volume of the metering device is defined by a chamber in which a piston is reciprocatingly mounted;   determining a movement amount of the metering piston within the chamber from a first position to a second position to increase a pressure in the sample loop from an essentially atmospheric pressure to the pump pressure based on the pump pressure;   loading the sample on the sample loop using the metering device;   with the sample loaded on the sample loop and with the sample loop remaining isolated from the high-pressure fluidic path and from the high pressure pump, decreasing the operative volume of the metering device to increase the pressure in the sample loop from the essentially atmospheric pressure to essentially correspond to the high pressure pump pressure of the high-pressure fluidic path, wherein the piston within the chamber is moved by the determined movement amount between the determined positions from the first position to the second position; and   using the valve comprising the motor and encoder to connect the sample loop to the high-pressure fluidic path so that the pump pressure from a high-pressure pump is applied to the sample loop to cause the sample in the sample loop to flow from the sample loop through a portion of the high-pressure fluidic path to the chromatography column;   wherein the metering device and the sample loop are always in fluid communication with one another.   
     
     
         24 . The method of  claim 23  further including:
 isolating the sample loop from the high-pressure fluidic path of the liquid chromatography system after the sample has flowed into the high-pressure fluidic path; and 
 increasing the volume of the metering device to reduce the pressure in the sample loop to the essentially atmospheric pressure. 
 
     
     
         25 . The method of  claim 23  wherein isolating the sample loop from the high-pressure fluidic path includes using the motor and encoder to place an injection valve in a PRESSURE COMPENSATION position in which
 first and second sample loop ports of the injection valve are closed so as to facilitate pressurization of the sample loop, and 
 first and second high-pressure ports of the injection valve are connected so as to operatively connect the high-pressure pump to the liquid chromatography column. 
 
     
     
         26 . The method of  claim 25  wherein placing the injection valve in the PRESSURE COMPENSATION position includes using the motor to rotate a rotor of the injection valve with respect to a stator of the injection valve. 
     
     
         27 . The method of  claim 23  wherein the piston is connected to a pump motor which is operable to move the metering piston within the chamber, and the method further comprises: determining a force transmitted to the piston from the pump motor. 
     
     
         28 . The method of  claim 22 , wherein at the PRESSURE COMPENSATION position,
 (i) first and second sample loop ports of the injection valve are closed so as to facilitate a pressurization of the sample loop, and   (ii) first and second high-pressure ports of the injection valve are connected so as to operatively connect a high-pressure pump in fluid communication with the high-pressure fluidic path to the liquid chromatography column.   
     
     
         29 . The method of  claim 22 , wherein placing the injection valve in the PRESSURE COMPENSATION position includes using the motor to rotate a rotor of the injection valve with respect to a stator of the injection valve and measuring rotation using the encoder. 
     
     
         30 . The method of  claim 22 , further comprising:
 operating the injection valve to connect the sample loop to the high-pressure fluidic path such that the pump pressure from a high-pressure pump of the liquid chromatography system is applied to the sample loop, and a sample in the sample loop flows from the sample loop into the high-pressure fluidic path and to the chromatography column.   
     
     
         31 . The method of  claim 30 , further comprising:
 after operating the injection valve to connect the sample loop, introducing the sample into the chromatography column;   isolating the sample loop from the high-pressure fluidic path by placing the injection valve back in the pressure compensation position using the motor and encoder; and   increasing the volume of the metering device to reduce the pressure in the sample loop from the pump pressure of the liquid chromatography column to the essentially atmospheric pressure.   
     
     
         32 . The method of  claim 22 , in which the piston comprises a metering piston. 
     
     
         33 . The method of  claim 28 , in which the sample loop includes a first connecting portion and a second connecting portion, in which the first connecting portion is connected to the first sample loop port of the injection valve and to the metering device, in which the second connecting portion is connected to the second sample loop port of the injection valve and to the metering device, in which the second connecting portion includes a needle and a seat capillary, in which the needle and the seat capillary are configured to be separated. 
     
     
         34 . The method of  claim 23 , in which the piston comprises a metering piston. 
     
     
         35 . The method of  claim 25 , in which the sample loop includes a first connecting portion and a second connecting portion, in which the first connecting portion is connected to the first sample loop port of the injection valve and to the metering device, in which the second connecting portion is connected to the second sample loop port of the injection valve and to the metering device, in which the second connecting portion includes a needle and a seat capillary, in which the needle and the seat capillary are configured to be separated. 
     
     
         36 . A method of operating a liquid chromatography system, the liquid chromatography system comprising a liquid chromatography column and an injection valve, the method comprising:
 using a valve to isolate a sample loop of the liquid chromatography system from a high-pressure fluidic path that is in fluid communication with the liquid chromatography column,   maintainingwherein the high-pressure fluidic path at a pump pressure with a high pressure pump,   wherein the sample loop is in fluid communication with the injection valve and the sample loop comprises a metering device configured for loading a sample on the sample loop, and isolating the sample loop comprises using a motor and encoder to place placing the injection valve in a PRESSURE COMPENSATION position, wherein the metering device comprises a chamber and a piston in the chamber;   determining a movement amount of the piston within the chamber from a first position to a second position to increase a pressure in the sample loop from an essentially atmospheric pressure to the pump pressure based on the pump pressure;   while the sample loop is isolated from the high-pressure fluidic path and the high pressure pump, forwarding the piston within the chamber by the determined movement amount from the first position to the second position to increase the pressure in the sample loop from the essentially atmospheric pressure to essentially correspond to the pump pressure of the high-pressure fluidic path; and   wherein the metering device and the sample loop are in fluid communication in each position of the injection valve.   
     
     
         37 . The method of  claim 36 , wherein at the PRESSURE COMPENSATION position,
 (i) first and second sample loop ports of the injection valve are closed so as to facilitate a pressurization of the sample loop, and   (ii) first and second high-pressure ports of the injection valve are connected so as to operatively connect a high-pressure pump in fluid communication with the high-pressure fluidic path to the liquid chromatography column.   
     
     
         38 . The method of  claim 36 , wherein placing the injection valve in the PRESSURE COMPENSATION position includes rotating a rotor of the injection valve with respect to a stator of the injection valve. 
     
     
         39 . The method of  claim 36 , further comprising:
 operating the injection valve to connect the sample loop to the high-pressure fluidic path such that the pump pressure from a high-pressure pump of the liquid chromatography system is applied to the sample loop, and a sample in the sample loop flows from the sample loop into the high-pressure fluidic path and to the chromatography column.   
     
     
         40 . The method of  claim 39 , further comprising:
 after operating the injection valve to connect the sample loop, introducing the sample into the chromatography column;   isolating the sample loop from the high-pressure fluidic path by using the motor and encoder to place the injection valve back in the PRESSURE COMPENSATION position; and   retracting the piston within the chamber from the second position to the first position to decrease the pressure in the sample loop to the essentially atmospheric pressure.   
     
     
         41 . The method of  claim 37 , in which the sample loop includes a first connecting portion and a second connecting portion, in which the first connecting portion is connected to the first sample loop port of the injection valve and to the metering device, in which the second connecting portion is connected to the second sample loop port of the injection valve and to the metering device, in which the second connecting portion includes a needle and a seat capillary, in which the needle and the seat capillary are configured to be separated. 
     
     
         42 . The method of  claim 36 , in which the piston comprises a metering piston. 
     
     
         43 . A method of injecting a sample into a chromatography column of a liquid chromatography system, the method comprising:
 isolating a sample loop of the liquid chromatography system from a high-pressure fluidic path of the liquid chromatography system in fluid communication with the chromatography column of the liquid chromatography system, wherein the high-pressure fluidic path is at a pump pressure, wherein the sample loop is in fluid communication with an injection valve of the liquid chromatography system and the sample loop comprises a sample conveying device for loading the sample on the sample loop and the isolating of the sample loop comprises placing an injection valve in a PRESSURE COMPENSATION position, wherein the sample conveying device comprises a pump volume and a plunger, in which the plunger is guided in the pump volume;   calculating a distance for a movement of the plunger within the pump volume from a first position to a second position to increase a pressure in the sample loop from an atmospheric pressure to the pump pressure based on a) a compressibility of a fluid in the sample conveying device and the sample loop and b) the pump pressure; and   loading the sample on the sample loop;   with the sample loaded on the sample loop and with the sample loop remaining isolated from the high-pressure fluidic path, decreasing the pump volume of the sample conveying device to increase the pressure in the sample loop from the atmospheric pressure to correspond to the pump pressure of the high-pressure fluidic path, wherein the decreasing of the pump volume includes forwarding the plunger within the pump volume by the calculated distance from the first position to the second position; and   connecting the sample loop to the high-pressure fluidic path so that the pump pressure from a high-pressure pump is applied to the sample loop to cause the sample in the sample loop to flow from the sample loop through a portion of the high-pressure fluidic path to the chromatography column.   
     
     
         44 . The method of  claim 43 , in which the calculating of the distance for the movement of the plunger within the pump volume from the first position to the second position to increase the pressure in the sample loop from the atmospheric pressure to the pump pressure is further based on c) an elasticity of the sample loop. 
     
     
         45 . The method of  claim 43 , in which the sample loop includes a first connecting piece and a second connecting piece, in which the first connecting piece is connected to a 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. 
     
     
         46 . The method of  claim 43 , in which the sample conveying device and the sample loop are in fluid communication in each position of the injection valve. 
     
     
         47 . The method of  claim 43 , wherein at the PRESSURE COMPENSATION position, i) first and second sample loop ports of the injection valve are closed so as to facilitate a pressurization of the sample loop, and ii) first and second high-pressure ports of the injection valve are connected so as to operatively connect a high-pressure pump in fluid communication with the high-pressure fluidic path to the chromatography column, the method further comprising:
 determining the compressibility of the fluid with the high-pressure pump.   
     
     
         48 . The method of  claim 43  further including: isolating the sample loop from the high-pressure fluidic path of the liquid chromatography system after the sample has flowed into the high-pressure fluidic path; and increasing the pump volume of the sample conveying device to reduce the pressure in the sample loop to the atmospheric pressure. 
     
     
         49 . The method of  claim 43  wherein the plunger is connected to a drive device which is operable to move the plunger within the pump volume, and the method further comprises:
 measuring a force exerted upon the plunger by the drive device. 
 
     
     
         50 . The method of  claim 44 , in which the compressibility of the fluid and the elasticity of the sample loop are stored in a control unit of the liquid chromatography system. 
     
     
         51 . The method of  claim 43 , in which the sample conveying device further comprises a syringe, in which the syringe contains the pump volume. 
     
     
         52 . A method of injecting a sample into a chromatography column of a liquid chromatography system, the liquid chromatography system comprising the chromatography column and an injection valve, the method comprising:
 isolating a sample loop of the liquid chromatography system from a high-pressure fluidic path in fluid communication with the chromatography column, wherein the high-pressure fluidic path is at a pump pressure, wherein the sample loop is in fluid communication with the injection valve and the sample loop comprises a sample conveying device for loading the sample on the sample loop, and the isolating of the sample loop comprises placing the injection valve in a PRESSURE COMPENSATION position,   wherein the sample conveying device comprises a pump volume and a plunger, in which the plunger is guided in the pump volume;   calculating a distance for a movement of the plunger within the pump volume from a first position to a second position to increase a pressure in the sample loop from an atmospheric pressure to the pump pressure based on a) a compressibility of a fluid in the sample conveying device and the sample loop, b) the pump pressure, and c) an elasticity of the sample loop;   loading the sample on the sample loop;   with the sample loaded on the sample loop and with the sample loop remaining isolated from the high-pressure fluidic path, forwarding the plunger within the pump volume by the calculated distance for the movement of the plunger within the pump volume from the first position to the second position to increase the pressure in the sample loop from the atmospheric pressure to the pump pressure, wherein the sample conveying device and the sample loop are in fluid communication in each position of the injection valve; and   connecting the sample loop to the high-pressure fluidic path so that the pump pressure from a high-pressure pump is applied to the sample loop to cause the sample in the sample loop to flow from the sample loop through a portion of the high-pressure fluidic path to the chromatography column.   
     
     
         53 . The method of  claim 52 , 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. 
     
     
         54 . The method of  claim 52 , in which the sample conveying device further comprises a syringe, in which the syringe contains the pump volume. 
     
     
         55 . A sample injector configured to load a sample into a sample loop at an atmospheric pressure and then to increase a pressure in the sample loop to a pump 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 plunger 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 plunger within the pump volume from a first position to a second position to increase the pressure in the sample loop from the atmospheric pressure to the pump pressure based on a compressibility of the sample in the sample conveying device and the sample loop, and the pump pressure; and 
 iii) control the sample conveying device to move the plunger 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 atmospheric pressure to the pump pressure. 
   
     
     
         56 . The sample injector of  claim 55 , in which the distance for the movement of the plunger within the pump volume from the first position to the second position to increase the pressure in the sample loop from the atmospheric pressure to the pump pressure is further based on an elasticity of the sample loop. 
     
     
         57 . The sample injector of  claim 55 , in which the control unit is further configured to
 iv) control the sample conveying device to move the plunger 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 atmospheric pressure.   
     
     
         58 . The sample injector of  claim 55 , 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. 
     
     
         59 . The sample injector of  claim 55 , in which the injection valve comprises a rotor and a stator. 
     
     
         60 . The sample injector of  claim 55  further comprising a drive device connected to the plunger and configured to move the plunger in the pump volume. 
     
     
         61 . The sample injector of  claim 55 , 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. 
     
     
         62 . The sample injector of  claim 55 , wherein at the LOAD position, the sample conveying device is configured to load the sample in the sample loop and wherein at the INJECT position, the injection valve is configured to inject the sample in the sample loop into a chromatography column. 
     
     
         63 . The method of  claim 55 , in which the sample conveying device further comprises a syringe, in which the syringe contains the pump volume. 
     
     
         64 . A liquid chromatography system comprising
 A) a high-pressure pump;   B) a chromatography column;   C) a sample injector configured to load a sample into a sample loop at an atmospheric pressure and then to increase a pressure in the sample loop to a pump 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 chromatography column; 
 
 b) a sample conveying device comprising:
 i) a pump volume and 
 ii) a plunger 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 atmospheric pressure to the pump pressure based on a compressibility of the sample in the sample conveying device and the sample loop, the pump pressure, and an elasticity of the sample loop; and 
 iii) control the sample conveying device to move the plunger 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 atmospheric pressure to the pump pressure. 
 
   
     
     
         65 . The liquid chromatography system of  claim 64 , in which the control unit is further configured to
 iv) control the sample conveying device to move the plunger 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 atmospheric pressure.   
     
     
         66 . The liquid chromatography system of  claim 64 , 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. 
     
     
         67 . The liquid chromatography system of  claim 64 , in which the injection valve comprises a rotor and a stator. 
     
     
         68 . The liquid chromatography system of  claim 64  further comprising a drive device connected to the plunger and configured to move the plunger in the pump volume. 
     
     
         69 . The liquid chromatography system of  claim 64 , 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. 
     
     
         70 . The liquid chromatography system of  claim 64 , wherein at the LOAD position, the sample conveying device is configured to load the sample in the sample loop and wherein at the INJECT position, the injection valve is configured to inject the sample in the sample loop into the chromatography column.