A methane analyzer system having a cutter for preparing a sample gas prior to submission to a hydrogen flame ionization detector includes a source dilution gas that is connected to the hydrogen flame ionization detector, and a flow restrictor line for directing a portion of the dilution gas to the cutter for mixing with the sample gas prior to introduction into the ionization detector. A source of fuel, such as hydrogen, which is connected to the ionization detector, is also metered in measured quantities to the cutter to stabilize the oxidation of the sample gas.