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) and passed by a needle electrode with a potential (see figure above). A glow discharge results, which creates both charged particles and excited-state species (gaseous metastables). The gas stream then passes through an additional electrode (electrode 1) to filter out charged particles, leaving only metastables. As the stream continues through the source, it flows through a tube that can be heated. Heating the gas allows for control of both thermal desorption and pyrolysis of samples in the sample gap. Next, the stream passes through a final grid electrode (electrode 2) to prevent any positive and negative ions from recombining as they exit the source. Finally, the dry gas exits through the insulator cap. The insulator cap ensures that the operator is well protected from any of the high voltages isolated within the source. 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). 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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