This high resolution Time-of-Flight mass spectrometer is primarily used for small organic analytes and low polarity materials. The instrument is equipped with electron ionization (EI), chemical ionization (CI), and field ionization/field desorption (FI/FD) ion sources. This instrument has a mass range up to m/z 800 in EI, CI, and FI modes and up to m/z 4000 in FD mode. Accurate mass measurement (<3 mDa) for elemental composition confirmation is available in EI and CI modes. The GCT Premier employs an Agilent 7890 A gas chromatograph and Agilent 7683 B autosampler in EI, CI, and FI modes.