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Technical Tips

A Technical Tip by Kory Kelly
GC Product Manager


It is advisable to use the highest purity gas possible. Ultra high purity (99.99 %), ultra pure carrier (99.995 %), or even research grade (99.9999 %) is preferred to minimize critical impurities, instrument downtime and troubleshooting.


Three types of gas are commonly used as a carrier gas:
1. Hydrogen (H2): Hydrogen will yield maximal number of theoretical plates for thin film columns and the high efficiency is largely retained at velocities higher than uopt. Hydrogen is not generally recommended due to its hazardous nature.


2. Helium (He): When hydrogen is not used, helium is the best alternative for speed and sensitivity.


3. Nitrogen (N 2): Nitrogen is the last choice for thin film columns. For thick film columns, nitrogen yields the highest number of theoretical plates. However, the optimal velocity is fairly low (long analysis times), and the loss in efficiency at higher velocities is high. If resolution is sufficient, hydrogen or helium are good alternatives.


Carrier Gas Selection and Velocity Optimization

Optimal velocities
for low df values
u opt
(cm/sec)
Optimal velocities
for low df values
u opt
(cm/sec)
H2 40 H2 25
He 25 He 15
N2 10 N2 7