The DART ion source was developed at JEOL USA by Robert B. Cody and James A. Laramée. The first working prototype was tested on an AccuTOF time-of-flight mass spectrometer early in 2003. The first patent awarded for the DART technology soon followed. A commercial version of the AccuTOF DART mass spectrometer system was introduced by JEOL USA at Pittcon 2005, where it won the Editors’ Gold Award for best new product. A second DART patent was awarded in 2006 (U.S. Patent # 7,112,785).
Direct Analysis in REAL Time (DART™) Ion Source
DART Ion Source Operation
Reference: Anal. Chem. 2005, 77, 2297-2302
Dry gas is introduced (usually helium) into a chamber with a needle electrode with a high electrical potential (see figure above). A glow discharge results, which creates both charged particles and long-lived excited-state species (metastable atoms). The gas stream exiting the glow discharge (“flowing afterglow”) contains primarily metastable atoms. As the stream continues through the source, it flows through an optionally heated tube. Heating the gas permits thermal desorption and/or pyrolysis of samples in the sample gap. The stream then passes through a grid or “exit” electrode to prevent positive and negative ions from recombining as they are formed when metastable atoms exiting the source contact atmospheric gas molecules. Finally, the dry gas exits through the insulator cap. The insulator cap ensures that the operator is protected from contact with the grid electrode potential. DART ionization of samples then occurs in the sample gap, which is at ground potential, room temperature and atmospheric pressure (i.e. completely ambient conditions). Samples are ionized either directly by energy transfer from metastable atoms or indirectly through reactions with ions from atmospheric gases. The ions formed are directed to the AccuTOF mass spectrometer inlet by both the gas flow and a slight vacuum on the spectrometer inlet.
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