mass spectrometry

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics, Chemistry) A method for identifying chemical composition of substances by use of a mass spectrometer.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics, analytical chemistry An analytical technique that measures the mass / charge ratio of the ions formed when a molecule or atom is ionized, vaporized and introduced into a vacuum. Mass spectrometry may also involve breaking molecules into fragments - thus enabling its structure to be determined.