Column flow parameters

Helium or hydrogen can be used as a carrier gas at a constant velocity of 20 cm/sec.  The GC holds the carrier gas velocity constant as the temperature and pressure change.  Check the system for leaks by placing small amounts of a column-compatible solvent (i.e. hexane, a mixture of isopropanol and water) around fittings, applying gas pressure to the system and observing for tiny bubbles. This should be done routinely especially after the installation of a new column to avoid chromatography degradation and accidental explosions (with hydrogen).