Answer :
Without specific information or guidelines regarding the optimal make-up gas flow rate for the given conditions in the GC system, 'None of the listed' is the most suitable answer. The exact optimal flow rate for make-up gas needs to be determined based on the GC system's requirements or manufacturer recommendations.
The question relates to the optimal volumetric flow rate of the make-up gas for a gas chromatography (GC) analysis using a flame ionization detector (FID), where helium (He) is used as the carrier gas. In this scenario, for a carrier gas flow rate of 1.4 mL/min through the column, the make-up gas flow rate is typically selected in a manner that maximizes the detector sensitivity and ensures efficient mixing with the analytes exiting the column. However, without additional information such as specific make-up gas flow recommendations from the manufacturer or experimental data, it is not possible to provide a precise answer to what the optimal make-up gas flow rate should be. Therefore, based on the choices provided, 'None of the listed' seems like an appropriate selection since we do not have a definitive flow rate that has been deemed optimal for the conditions described.
