HELIUM DROPLET MASS SPECTROMETERY (HDMS)

摘要

A method and device for mass spectrometry analysis, wherein a massspectrometeris adapted for use with helium droplets, as an ionization site medium, with aproton beinginitially captured by a large helium droplet (-10,000 helium atoms) and thencooledevaporatively to 0.4 Kelvin. The protonated helium droplet then picks up aneutral moleculeof interest and the neutral molecule is protonated inside of the droplet withthe liquid heliumdroplet acting as a heat bath to provide rapid cooling of the newly formedprotonatedmolecule. As a result, there is essentially no energy available, at 0.4Kelvin, for theprotonated molecule to fragment. Remaining liquid helium is removed and thestablymaintained protonated molecule is detected by a mass spectrometer. Since themolecules donot fragment when protonated (ionized), each compound in a mixture analysesgives onemass and the number of ions of a particular mass detected is directlyproportional to themolar percentage of that mass in the sample. The device for effecting themethod, comprisesthe elements of : (1) Helium cluster or droplet source; (2) Proton source forintroduction ofprotons to the droplet (i.e., ionization); (3) atmospheric pressure (AP)Source for reduction ofpressure to form a low pressure stream; (4) Cell pick-up elements wherecompoundmolecules are protonated or ionized at low temperature; (5) Desolvation areafor removal ofresidual helium; and (6) Mass spectrometer and detector.