Sample Injector For Liquid Chromatography, Particularly For High Performance Liquid Chromatography

Abstract

A sample injector for liquid chromatography includes 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 for liquid chromatography, the sample injector including:
 (a) an injection valve having a waste port, first and second sample loop ports, and first and second high-pressure ports, the first high-pressure port adapted to be connected to a HPLC pump and the second high-pressure port adapted to be connected to a chromatography column;   (b) a sample loop having (i) a first sample loop section operatively connected between the first sample loop port and a pump volume of a sample conveying device, (ii) a second sample loop section operatively connected between the second sample loop port and the pump volume of the sample conveying device, and (iii) an intake arrangement connected in the sample loop operable to selectively provide an opening in the sample loop to facilitate the intake of a sample fluid into a volume of the sample loop; and   (c) wherein the injection valve includes (i) a LOAD position in which the first and second high-pressure ports are connected to one another and isolated from the sample loop, and (ii) a PRESSURE COMPENSATION position in which the first and second sample loop ports are closed so as to facilitate pressurization of the sample loop by the sample conveying device to essentially an operating pressure of the chromatography column, and (iii) an INJECT position in which the first high-pressure port is operatively connected to the first sample loop port and the second high-pressure port is operatively connected to the second sample loop port so as to facilitate a flow of the sample fluid in the sample loop into the second sample loop port and toward the second high-pressure port under a pressure applied to the first high-pressure port.   
     
     
         2 . The sample injector of  claim 1  wherein the sample conveying device includes:
 (a) a device body having a cavity formed therein; 
 (b) a movable element mounted in the cavity of the device body, with the pump volume of the sample conveying device defined between the cavity of the device body and the moveable element, the moveable element being movable with respect to the device body to vary the pump volume; and 
 (c) a drive operatively connected to move the movable element with respect to the device body. 
 
     
     
         3 . The sample injector of  claim 2  wherein the first sample loop portion is connected to the pump volume of the sample conveying device at a first end of the cavity formed in the device body and the second sample loop section is connected to the pump volume of the sample conveying device at a second end of the cavity formed in the device body opposite the first end of the cavity. 
     
     
         4 . The sample injector of  claim 2  wherein the second sample loop section is connected to the pump volume of the sample conveying device at a first point along the length of the cavity formed in the device body and the first sample loop section is connected to the pump volume of the sample conveying device at a second point along the length of the cavity formed in the device body, the second point being spaced apart from the first point along the length of the cavity. 
     
     
         5 . The sample injector of  claim 2  further including a control unit operable to control the movement of the movable element of the sample conveying device. 
     
     
         6 . The sample injector of  claim 5  wherein the control unit is also operable to place the injection valve in any of the LOAD position, PRESSURE COMPENSATION position, and INJECT position. 
     
     
         7 . The sample injector of  claim 1  wherein in the LOAD position the second sample loop port is operatively connected to the waste port. 
     
     
         8 . The sample injector of  claim 1  wherein the first and second high-pressure ports are connected when the injection valve is in the PRESSURE COMPENSATION position. 
     
     
         9 . A sample injector for liquid chromatography, the sample injector including:
 (a) an injection valve having first and second sample loop ports, and first and second high-pressure ports, the first high-pressure port adapted to be connected to a HPLC pump and the second high-pressure port adapted to be connected to a chromatography column;   (b) a sample conveying device having a device body with a cavity formed therein and a movable element mounted in the cavity so as to define a pump volume of the sample conveying device between the surface of the cavity and an outer surface of the movable element;   (c) a drive operatively connected to move the movable element with respect to the device body to vary the pump volume;   (d) a sample loop having (i) a first sample loop section operatively connected between the first sample loop port and the pump volume of a sample conveying device, (ii) a second sample loop section operatively connected between the second sample loop port and the pump volume of the sample conveying device, and (iii) an intake arrangement operable to selectively provide an opening in the sample loop to facilitate the intake of a sample fluid into the sample loop; and   (e) wherein the injection valve includes (i) a LOAD position in which the first and second high-pressure ports are connected to one another and isolated from the sample loop, and (ii) a PRESSURE COMPENSATION position in which the first and second sample loop ports are closed so as to facilitate pressurization of the sample loop by the sample conveying device to essentially the operating pressure of the chromatography column, and (iii) an INJECT position in which the first high-pressure port is operatively connected to the first sample loop port and the second high-pressure port is operatively connected to the second sample loop port so as to facilitate a flow of the sample fluid in the sample loop into the second sample loop port and toward the second high-pressure port under a pressure applied to the first high-pressure port.   
     
     
         10 . The sample injector of  claim 9  wherein the first sample loop portion is connected to the pump volume of the sample conveying device at a first end of the cavity formed in the device body and the second sample loop section is connected to the pump volume of the sample conveying device at a second end of the cavity formed in the device body opposite the first end of the cavity. 
     
     
         11 . The sample injector of  claim 9  wherein the second sample loop section is connected to the pump volume of the sample conveying device at a first point along the length of the cavity formed in the device body and the first sample loop section is connected to the pump volume of the sample conveying device at a second point along the length of the cavity formed in the device body, the second point being spaced apart from the first point along the length of the cavity. 
     
     
         12 . The sample injector of  claim 9  further including a control unit operable to control the movement of the movable element of the sample conveying device. 
     
     
         13 . The sample injector of  claim 12  wherein the control unit is also operable to place the injection valve in any of the LOAD position, PRESSURE COMPENSATION position, and INJECT position. 
     
     
         14 . The sample injector of  claim 9  wherein when the injection valve is in the PRESSURE COMPENSATION position and the pressure in the sample loop is ambient pressure, the drive is selectively operative to move the movable element relative to the device body so as to increase the pressure in the sample loop to the operating pressure of the chromatography column. 
     
     
         15 . The sample injector of  claim 9  wherein when the injection valve is in the PRESSURE COMPENSATION position and the pressure in the sample loop is at the operating pressure of the chromatography column, the drive is selectively operative to move the movable element relative to the device body so as to decrease the pressure in the sample loop to ambient pressure. 
     
     
         16 . A liquid chromatography system including:
 (a) a HPLC pump;   (b) a chromatography column;   (c) an injection valve having first and second sample loop ports and first and second high-pressure ports, the first high-pressure port connected to the HPLC pump and the second high-pressure port connected to the chromatography column;   (d) a sample loop having (i) a first sample loop section operatively connected between the first sample loop port and a pump volume of a sample conveying device, (ii) a second sample loop section operatively connected between the second sample loop port and the pump volume of the sample conveying device, and (iii) an intake arrangement connected in the sample loop operable to selectively provide an opening in the sample loop to facilitate the intake of a sample fluid into a volume of the sample loop; and   (e) wherein the injection valve includes (i) a LOAD position in which the first and second high-pressure ports are connected to one another and isolated from the sample loop, and (ii) a PRESSURE COMPENSATION position in which the first and second sample loop ports are closed so as to facilitate pressurization of the sample loop by the sample conveying device to essentially the operating pressure of the chromatography column, and (iii) an INJECT position in which the first high-pressure port is operatively connected to the first sample loop port and the second high-pressure port is operatively connected to the second sample loop port so as to facilitate a flow of the sample fluid in the sample loop into the second sample loop port and toward the second high-pressure port under a pressure applied by the HPLC pump to the first high-pressure port.   
     
     
         17 . The liquid chromatography system of  claim 16  wherein the sample conveying device includes:
 (a) a device body having a cavity formed therein; 
 (b) a movable element mounted in the cavity of the device body, with the pump volume of the sample conveying device defined between the cavity of the device body and the moveable element, the moveable element being movable with respect to the device body to vary the pump volume; and 
 (c) a drive operatively connected to move the movable element with respect to the device body. 
 
     
     
         18 . The liquid chromatography system of  claim 17  wherein the first sample loop portion is connected to the pump volume of the sample conveying device at a first end of the cavity formed in the device body and the second sample loop section is connected to the pump volume of the sample conveying device at a second end of the cavity formed in the device body opposite the first end of the cavity. 
     
     
         19 . The liquid chromatography system of  claim 17  wherein the second sample loop section is connected to the pump volume of the sample conveying device at a first point along the length of the cavity formed in the device body and the first sample loop section is connected to the pump volume of the sample conveying device at a second point along the length of the cavity formed in the device body, the second point being spaced apart from the first point along the length of the cavity. 
     
     
         20 . The liquid chromatography system of  claim 17  wherein when the injection valve is in the PRESSURE COMPENSATION position and the pressure in the sample loop is ambient pressure, the drive is selectively operative to move the movable element relative to the device body so as to increase the pressure in the sample loop to the operating pressure of the chromatography column.