TCD of hydrogen in argon carrier

[rekuci]

Does anyone have experience with the analysis of gas mixtures containing hydrogen in argon carrier gas?

I'm seeing a strange effect when constructing calibrations curves from either (1) injecting different volumes of pure hydrogen, or (2) injecting the same volume of mixtures containing different %'s hydrogen with balance air. For the same molar quantity of hydrogen, the H2 peak area becomes much smaller in the H2/air mixtures (becomes extreme below 40-50% H2) than in the smaller volume of pure H2. For example, the peak area of 22% H2 is about 100x smaller than the same molar quantity of 100% H2. These areas are reproducible from injection to injection and all the data fit together to form decent, nearly linear curves.

The only way I could think of to explain this effect is local concentration variation of hydrogen, because the 'slug' of hydrogen exiting the column in a dilute mixture will be more spread out than in the pure sample, therefore heavier in argon, with a reduced thermal conductivity. But even this ridiculous explanation (with empirical calculations of k of the mixture) doesn't seem to explain the huge difference.

Thanks for any suggestions.

[chromatographer1]

Historically, H2 analysis is done with nitrogen carrier.

I believe your experience demonstrates why that is the case, although I never knew why argon was not a good solution.

Thanks for sharing your difficulties with Argon carrier performing H2 analysis. It has been educational for many of us on the Forum.

best wishes,

Rod