Abstract: | Two scanning modes can be used sequentially to determine the relative abundances of a series of daughter ions formed from the same parent ion in the field free region preceding the first sector of a double focusing mass spectrometer. Hydrogen exchange reactions in the molecular ions of benzoic acid and anisole have been analysed by these procedures, and a study of diphenylmethane demonstrates that the usual procedure of single scans gives rise to peaks that might be interpreted erroneously. |