Gas analysis
N2, O2, Ar, CO2, CH4, He, and H2 are determined by a quadrupole mass spectrometer (QMS). A complete QMS analysis with detection limits between 1 and 20 ppmv (parts per million by volume) is achieved with this setup after an integration time of less than 30 s. However, a sampling interval of one minute is mostly chosen to reduce the amount of data produced. Hydrocarbons (CH4, C2H6, C3H8, i-C4H10, and n-C4H10) are analyzed at 10 min intervals with an automated standard field GC, which is equipped with a flame ionization detector. Detection limits for the hydrocarbons are at about 1 ppmv. Gas samples for further studies e.g. of isotopes are taken automatically when a given threshold level at the QMS is exceeded.