Polar stationary phases and hydrogen as carrier gas in GC

Question

Hello Agilent, Could hydrogen used as carrier gas in capillary gas chromatography harm or degrade some types of polar stationary phases? Best regards - Lars

Dr. Know · Accepted Answer

Hi Lars, Hydrogen is the best possible carrier gas for almost all GC separations (my opinion, but it's cheap, fast and can come from a gas generator) and is not damaging any stationary phase. You will loose a little in the plate counts, but because the separation is twice as fast as with helium, band broadening due to diffusion goes down and the peaks are sharper (perfect for chiral separations). Norbert

Dr. Know · Answer

Just to be precise, petertran talks about PLOT columns (solid stationary phases) with adsorption processes, not WCOT columns (liquid stationary phases) with partitioning.

The catalytic effect of some Al₂O₃ phases on unsaturated hydrocarbons will lead to strange peak shapes as described here.

Secondly phase polarity is defined for liquid phases as the sum of the first five McReynolds constants (with or without normalization), but is solely based on partitioning chromatography. Used with PLOT columns the normalized sum is always greater than 100, falsely indicating a highly polar phase.

Norbert

petertran · Answer

Hi Lars,

I would add an input from my experience that H2 carrier gas may cause some chemical reactions on some specific polar columns and compounds. Two scenarios I have encountered were (1) analysis of C4-C5 olefins on an AL2O3 PLOT column where some olefins react with H2 and form paraffins and (2) analysis of oxygen containing compounds on an Lowox column where you would see a lot of FID spikes. I’m not sure what reactions were but switching to He or N2 made those spikes disappeared.

Peter.

Polar stationary phases and hydrogen as carrier gas in GC

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