Tech Tip

Why use hydrogen as your carrier gas?

Hydrogen, helium, or nitrogen - which do you choose as your carrier gas? We need only look at the van Deemter curves to see the advantages of hydrogen as a carrier gas.Nitrogen generates the highest column efficiency (HETP = 0.22mm), but at an optimum velocity of only 8-10 cm/sec. This great sacrifice in the speed of analysis generally makes nitrogen a poor choice. Column efficiency is slightly reduced with helium (HETP = 0.29mm), but optimum linear velocity is 19-22 cm/sec. With an optimum linear velocity of 35-42cm/sec., hydrogen combines high column efficiency (HETP = 0.28mm) with analysis times 4x faster than nitrogen and 2x faster than helium, thus reducing costs per analysis. Linear velocities of up to 75-80cm/sec. can be used with only a small decrease in column efficiency. Another benefit: lower temperatures are needed to elute analytes, increasing column longevity.