A low-pressure glow discharge that sputters and ionizes a solid sample, with subsequent mass analysis of the ions, constitutes glow discharge mass spectrometry (GD-MS). The discharge is typically a direct-current or radiofrequency plasma in argon; cathodic sputtering releases atoms from the specimen, and those atoms are ionized in the plasma by Penning and electron-impact processes ^[1]. The resulting elemental ions are extracted into a magnetic-sector or quadrupole mass analyzer, so that the spectrum reports elemental and isotopic composition of the solid rather than a molecular fragmentation pattern ^[2]. Atmospheric-pressure glow-discharge and flowing-afterglow variants ionize vapors or thermally desorbed organics at higher pressure and are related ionization sources rather than the classical solids GD-MS experiment ^[3]. Conceptual boundaries exclude inductively coupled plasma mass spectrometry of solutions, spark-source mass spectrometry, and optical glow-discharge emission spectrometry that does not mass-analyze ions. Essential features are a glow-discharge ion source, a conducting or radiofrequency-coupled sample, and a mass analyzer that records the sputtered ions.