DART (Direct Analysis in Real Time) is a new ion source that can analyze samples with various states and shapes without any sample preparation.

　　JEOL, the pioneer of ambient ionization

　　DART was born in 2003 at the mass spectrometry applications laboratory of JEOL USA, Inc. Among a series of new ionization techniques, which were later termed “ambient ionization,” DART was the first to have been invented and the first to have been commercialized in 2005. It was introduced at the Pittsburgh Conference in February 2005 and awarded the Pittcon Editor’s Gold Award as one of the best new products of the year. It was also awarded for the R&D 100 Award in September of the same year.

　　Direct analysis without sample preparation

　　You can acquire high mass-resolution, accurate-mass spectra in real time by simply presenting samples of various shapes and states to the DART ion source without any sample preparation. DART can handle samples with arbitrary shapes or “dirty” sample that conventional analytical method cannot deal with.

　　Direct analysis of liquid

　　Direct analysis of solid

　　Direct analysis of powder

　　AccuTOF LC-plus 4G + DART: the perfect combination

　　The DART was developed for the JEOL AccuTOF series of mass spectrometers. No additional interface is required between the DART and the AccuTOF LC-plus 4G due to a rugged, simple API interface and high-capacity vacuum pumping system. The combination is able to detect a wider range of polar and nonpolar compounds than any other DART MS system. With no additional interface, there is virtually no carryover from one analysis to another, even for “dirty” and “sticky” samples.

　　Nonpolar: organic electro-luminescence materials

　　Polar: an ionic liquid

　　Principle of DART ionization

　　DART ionization is based on the interaction between excited state atoms or molecules, and atmospheric gas and/or analytes.

　　Plasma is generated by glow discharge from the needle electrode in a helium gas stream. The plasma includes ions, electrons, and excited state (metastable) atoms or molecules. The majority of charged particles are eliminated by the grounded electrode and the excited state neutral species are expelled to the atmosphere.

　　The gas stream can be heated by the gas heater to help analytes vaporization or desorption from the substrate surface.

　　Positive ion

　　The metastable helium atoms formed in the DART source react with atmospheric water to produce ionized water clusters. These protonated water clusters can then react with the analyte (M) to form protonated cations:

　　He(23S) + H2O → H2O+. + He(11S) + e-

　　H2O+. + H2O → H3O+ + OH.

　　H3O+ + nH2O → [(H2O)n+1 + H]+

　　[(H2O)n+1 + H]+ + M → [M + H]+ + (n+1)H2O

　　Negative ion

　　Metastable helium atoms can react with a neutral (N), such as the exit grid electrode, or another neutral species to form electrons through Penning ionization. The electrons formed are rapidly thermalized by collisions with atmospheric gases (G) and then react with gaseous oxygen to produce oxygen anions.

　　He(23S) + N → N+. + He(11S) + e-*

　　e-* + G → G* + e-

　　e- + O2 → O2-

　　These oxygen anions can then react with sample molecules (M) to produce analyte anions.

　　O2-. + M → [M - H]- + OOH.

　　O2-. + M → M-. + O2

　　O2-. + M → [M + O2]-.

　　Direct analysis of liquid

　　Direct analysis of solid

　　Direct analysis of powder

　　AccuTOF LC-plus 4G + DART: the perfect combination

　　The DART was developed for the JEOL AccuTOF series of mass spectrometers. No additional interface is required between the DART and the AccuTOF LC-plus 4G due to a rugged, simple API interface and high-capacity vacuum pumping system. The combination is able to detect a wider range of polar and nonpolar compounds than any other DART MS system. With no additional interface, there is virtually no carryover from one analysis to another, even for “dirty” and “sticky” samples.

　　Nonpolar: organic electro-luminescence materials

　　Polar: an ionic liquid

　　Principle of DART ionization

　　DART ionization is based on the interaction between excited state atoms or molecules, and atmospheric gas and/or analytes.

　　Plasma is generated by glow discharge from the needle electrode in a helium gas stream. The plasma includes ions, electrons, and excited state (metastable) atoms or molecules. The majority of charged particles are eliminated by the grounded electrode and the excited state neutral species are expelled to the atmosphere.

　　The gas stream can be heated by the gas heater to help analytes vaporization or desorption from the substrate surface.

　　Positive ion

　　The metastable helium atoms formed in the DART source react with atmospheric water to produce ionized water clusters. These protonated water clusters can then react with the analyte (M) to form protonated cations:

　　He(23S) + H2O → H2O+. + He(11S) + e-

　　H2O+. + H2O → H3O+ + OH.

　　H3O+ + nH2O → [(H2O)n+1 + H]+

　　[(H2O)n+1 + H]+ + M → [M + H]+ + (n+1)H2O

　　Negative ion

　　Metastable helium atoms can react with a neutral (N), such as the exit grid electrode, or another neutral species to form electrons through Penning ionization. The electrons formed are rapidly thermalized by collisions with atmospheric gases (G) and then react with gaseous oxygen to produce oxygen anions.

　　He(23S) + N → N+. + He(11S) + e-*

　　e-* + G → G* + e-

　　e- + O2 → O2-

　　These oxygen anions can then react with sample molecules (M) to produce analyte anions.

　　O2-. + M → [M - H]- + OOH.

　　O2-. + M → M-. + O2

　　O2-. + M → [M + O2]-.