Carrier Gas

[Victor]

I once encountered distorted peaks in the analysis of sterol TMS derivatives using hydrogen as a carrier gas. There were never any problems when using helium. I thought this might be due to some sort of hydrogenation of the sterol double bonds at the high temperatures of the system (around 250 degrees). If this were true, it might indicate potential problems at the column end as well as the mass spec end. However, it could be a rare example but was definitely attributable to the use of hydrogen.

[Peter Apps]

Hi Victor

Was it the chromatographic peaks that were distorted, or the mass peaks ? If the sterols were hydrogenating I would think that there must have been some dirt in the system that was acting as a catalyst. Come to think of it I vaguely remember seeing something about hydrogen reducing metallic oxide dirt in hot inlets.

Peter

[Victor]

Hi Peter,

This was definitely a chromatography problem as I noted it on a GC-FID system. I think you could be right about dirt catalysing such a reaction- or it could be residues of materials used in e.g. column deactivating processes (during column preparation) that could provide catalytic sites.

[chromatographer1]

Metal components used in MS detectors in the presence of hydrogen will hydrogenate double bonds.

Hydrogen carrier gas does not exactly reproduce the spectra of analytes recorded in databases and used for many legal issues.

Legal issues are the primary reason hydrogen carrier is not used for MS spectra.

However, for pure research and cost savings I do not see a problem.

Just don't submit any papers to journals using MS with hydrogen carrier.

At least, that is my advice.

best wishes,

Rod