A method comprising pressurizing a flow path connected to a separation column with a mobile phase fluid comprising liquefied CO2; then pressurizing fluidic tubing (260a, 260b) and a sample loop containing a sample slug with the mobile phase fluid; and then establishing fluidic communication between the fluidic tubing (260a, 260b) and the separation column and thereby introducing the sample slug into the pressurized flow path, wherein the flow path fluidically connects an auxiliary valve and the separation column, and wherein the fluidic tubing (260a, 260b) fluidically connects the auxiliary valve and an inject valve, wherein the auxiliary valve comprises: an auxiliary valve stator comprising a first plurality of stator ports (1, 2, 3, 4, 5, 6); and an auxiliary valve rotor comprising a first plurality of grooves (226a, 226b, 226c) wherein the auxiliary valve rotor is rotatable, relative to the auxiliary valve stator, between a plurality of discrete positions to form different fluidic passageways within the auxiliary valve; wherein the inject valve comprises: an inject valve stator comprising a second plurality of stator ports (1', 2', 3', 4', 5', 6'); and an inject valve rotor comprising a second plurality of grooves (246a, 246b, 246c), wherein the inject valve rotor is rotatable, relative to the inject valve stator, between a plurality of discrete positions to form different fluidic passageways within the inject valve, wherein the respective positions of the auxiliary valve rotor and the inject valve rotor are coordinated to form plurality of discrete configurations for performing the steps of pressurizing the flow path, pressurizing the fluidic tubing (260a, 260b) and the sample loop, and establishing fluidic communication between the fluidic tubing (260a, 260b) and the separation column, and wherein the step of establishing the fluidic communication between the fluidic tubing (260a, 260b) and the separation column is performed while the auxiliary valve rotor is in an inject position and the inject valve rotor is in an inject position which places the sample loop in fluidic communication with the fluidic tubing (260a, 260b) such that the mobile phase fluid flows from one or more pumps (112, 118) to the auxiliary valve, then from the auxiliary valve to the inject valve, and then back to the auxiliary valve, and then to the flow path. pressurizing a flow path connected to a separation column with a mobile phase fluid comprising liquefied CO2; then pressurizing fluidic tubing (260a, 260b) and a sample loop containing a sample slug with the mobile phase fluid; and then establishing fluidic communication between the fluidic tubing (260a, 260b) and the separation column and thereby introducing the sample slug into the pressurized flow path, wherein the flow path fluidically connects an auxiliary valve and the separation column, and wherein the fluidic tubing (260a, 260b) fluidically connects the auxiliary valve and an inject valve, wherein the auxiliary valve comprises: an auxiliary valve stator comprising a first plurality of stator ports (1, 2, 3, 4, 5, 6); and an auxiliary valve rotor comprising a first plurality of grooves (226a, 226b, 226c) an auxiliary valve stator comprising a first plurality of stator ports (1, 2, 3, 4, 5, 6); and an auxiliary valve rotor comprising a first plurality of grooves (226a, 226b, 226c) wherein the auxiliary valve rotor is rotatable, relative to the auxiliary valve stator, between a plurality of discrete positions to form different fluidic passageways within the auxiliary valve; wherein the inject valve comprises: an inject valve stator comprising a second plurality of stator ports (1', 2', 3', 4', 5', 6'); and an inject valve rotor comprising a second plurality of grooves (246a, 246b, 246c), an inject valve stator comprising a second plurality of stator ports (1', 2', 3', 4', 5', 6'); and an inject valve rotor comprising a second plurality of grooves (246a, 246b, 246c), wherein the inject valve rotor is rotatable, relative to the inject valve stator, between a plurality of discrete positions to form different fluidic passageways within the inject valve, wherein the respective positions of the auxiliary valve rotor and the inject valve rotor are coordinated to form plurality of discrete configurations for performing the steps of pressurizing the flow path, pressurizing the fluidic tubing (260a, 260b) and the sample loop, and establishing fluidic communication between the fluidic tubing (260a, 260b) and the separation column, and wherein the step of establishing the fluidic communication between the fluidic tubing (260a, 260b) and the separation column is performed while the auxiliary valve rotor is in an inject position and the inject valve rotor is in an inject position which places the sample loop in fluidic communication with the fluidic tubing (260a, 260b) such that the mobile phase fluid flows from one or more pumps (112, 118) to the auxiliary valve, then from the auxiliary valve to the inject valve, and then back to the auxiliary valve, and then to the flow path.