Sample injector with metering device balancing pressure differences in an intermediate valve state
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, wherein the sample loop is in fluid communication with the injection valve and the sample loop comprises a metering device for loading a sample on the sample loop, and isolating the sample loop comprises placing the injection valve in a PRESSURE COMPENSATION position, wherein a volume of the metering device is defined by a chamber in which a piston is reciprocatingly mounted;
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; and
while the sample loop is isolated from the high-pressure fluidic path, decreasing the volume of the metering device 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;
wherein decreasing the 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.
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 2 , 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.
4 . 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.
5 . The method of claim 1 , 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.
6 . The method of claim 5 , 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 metering device to reduce the pressure in the sample loop from the pump pressure of the liquid chromatography column to the essentially atmospheric pressure.
7 . The method of claim 1 , in which the piston comprises a metering piston.
8 . A method of injecting a sample in 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 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 metering device for loading a sample on the sample loop, wherein a volume of the metering device is defined by a chamber in which a piston is reciprocatingly mounted;
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;
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 volume of the metering device 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, wherein the piston within the chamber is moved by the determined movement amount 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;
wherein the metering device and the sample loop are always in fluid communication with one another.
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
increasing the volume of the metering device to reduce the pressure in the sample loop to the essentially atmospheric pressure.
10 . The method of claim 8 wherein isolating the sample loop from the high-pressure fluidic path includes placing 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.
11 . The method of claim 10 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.
12 . The method of claim 10 , 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.
13 . The method of claim 8 wherein the piston is connected to a pump motor which is operable to move the piston within the chamber, and the method further comprises: determining a force transmitted to the piston from the pump motor.
14 . The method of claim 8 , in which the piston comprises a metering piston.
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 metering device for loading a sample on the sample loop, and isolating the sample loop comprises 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, 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.
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 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.
18 . The method of claim 15 , 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.
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 placing 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.
21 . The method of claim 15 , in which the piston comprises a metering piston.