The peaks on masses 19, 37 and 55 m/z (and their isotopes) represent the reagent ions (H3O+) and their clusters. On 30 and 32 m/z NO+ and O2+, which are both impurities originating from the ion source, appear. All other peaks correspond to the multitude of compounds present in typical laboratory air (e.g. protonated acetone on 59 m/z).

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