How to Choose the Right Chemical Ionization Gas for Mass Spectrometry

Determine what kind of analyzer your gas chromatograph uses; this will determine what kind of sensor your machine uses to analyze the unknown solution, as not all analyzers require the same inert gases. Common analyzers include hot wire detectors, flame ionization detectors, electron capture detectors and thermo-ionic detectors. Refer to the equipment's documentation for suggested ionization gases.

Decide before you run the experiment whether you will use one or two gas columns and whether these columns will be capillary or packed columns -- the gas chambers in which you will analyze the unknown solution. Packed columns can handle noble gases like argon that capillary columns cannot.

Select lighter gases like hydrogen when you plan on using capillary columns in your experiment.

Consult previous experiments that have already been performed on unknown solutions using the same type of equipment. Gas chromatography equipment is expensive, and a laboratory will keep it for many years; over time, scientists begin to understand the sensitives of the machine and under what conditions it operates best. Talk to other scientists in your office or lab to see what inert gases will ionize best in your equipment.

Run your experiment with the same unknown solution two different times -- once using a light gas, like hydrogen, and one using a heavier gas, like nitrogen. If the results are clearer with the lighter gas, continue to use light gasses, such as helium and hydrogen, for further experiments.