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 injecting a sample volume into a chromatography column of a chromatography system, the chromatography system comprising:
 a sample loop in fluid communication with an injection valve, wherein the sample loop comprises a sample conveying device for loading the sample volume in the sample loop, wherein the sample conveying device comprises a pump volume structure and a moveable element, wherein the moveable element is guidable within the pump volume structure; and   a high-pressure fluidic path in fluid communication with the chromatography column and a high-pressure pump, wherein the method comprising:   flowing an eluent into the high-pressure fluidic path at a pump pressure generated by the high-pressure pump;   isolating the sample loop from the high-pressure fluidic path, wherein the isolating of the sample loop comprises placing the injection valve in a PRESSURE COMPENSATION position;   while the sample loop is isolated from the high-pressure fluidic path, sucking the sample volume into the sample loop from a sample vial by moving the moveable element with a stepping motor relative to the pump volume structure;   while the sample volume is loaded into the sample loop, and while the sample loop is isolated from the high-pressure fluidic path, moving the moveable element relative to the pump volume structure, a predetermined first distance, wherein the predetermined first distance is based at least in part upon a compressibility of the eluent in the sample loop and the pump pressure;   while the compressed sample volume is compressed to the high pressure, connecting the sample loop to the high-pressure fluidic path; and   while the compressed sample volume is compressed to the high pressure, conveying the compressed sample volume from the sample loop to the chromatography column.   
     
     
         2 . The method of  claim 1 , wherein the sample loop includes a first connecting piece and a second connecting piece, wherein the first connecting piece is connected to a first sample loop port of the injection valve and to the sample conveying device, wherein the second connecting piece is connected to a second sample loop port of the injection valve and to the sample conveying device, wherein the second connecting piece includes an intake segment and a feed segment, wherein the intake segment and the feed segment are configured to be separated. 
     
     
         3 . The method of  claim 1 , wherein in 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 the 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 eluent with the high-pressure pump.   
     
     
         4 . The method of  claim 1  further including:
 after the compressed sample volume has been conveyed from the sample loop to the chromatography column, isolating the sample loop from the high-pressure fluidic path; and 
 while the sample loop is isolated from the high-pressure fluidic path, moving the moveable element relative to the pump volume structure, a predetermined second distance, to thereby decompress the sample loop to a pressure that essentially corresponds to an atmospheric pressure. 
 
     
     
         5 . The method of  claim 1 , wherein the moveable element is connected to the stepping motor which is operable to move the moveable element within the pump volume structure, and the method further comprises:
 measuring a force exerted upon the moveable element by the stepping motor.   
     
     
         6 . The method of  claim 1 , wherein the compressibility of the eluent and an elasticity of the sample loop are stored for use by the chromatography system. 
     
     
         7 . The method of  claim 1 , wherein the pump volume structure comprises a syringe and the moveable element comprises a plunger. 
     
     
         8 . The method of  claim 1 , wherein the sample volume comprises the eluent, wherein the predetermined first distance is also based at least in part upon an elasticity of the sample loop. 
     
     
         9 . The method of  claim 1 , wherein the stepping motor comprises an integrated sensor measuring a force applied by the stepping motor on the moveable element. 
     
     
         10 . The method of  claim 1  further comprising:
 after the compressed sample volume has been conveyed from the sample loop to the chromatography column, isolating the sample loop from the high-pressure fluidic path; and 
 while the sample loop is isolated from the high-pressure fluidic path, moving the moveable element relative to the pump volume structure, a predetermined second distance, wherein the predetermined second distance is based at least in part upon a compressibility of an eluent in the sample loop, to thereby decompress the sample loop to a pressure that essentially corresponds to an atmospheric pressure. 
 
     
     
         11 . The method of  claim 10 , wherein the predetermined second distance is also based at least in part upon the pump pressure.