or mass spectroscopy
Analytic technique by which chemical substances are identified by sorting gaseous ions by mass using electric and magnetic fields.
A mass spectrometer uses electrical means to detect the sorted ions, while a mass spectrograph uses photographic or other nonelectrical means; either device is a mass spectroscope. The process is widely used to measure masses and relative abundances of different isotopes , to analyze products of a separation by liquid or gas chromatography , to test vacuum integrity in high-vacuum equipment, and to measure the geological age of minerals.