A New Ionization for Rapid, Non-contact, Surface Sampling of Compounds
What is DART®?
DART® stands for Direct Analysis in Real Time. It is a new ionization for rapid, non-contact surface sampling of compounds. Operating at ambient pressure with the sample at ground potential, the source enables near instantaneous determination of sample composition by using mass spectrometry. Electronic or vibronic excited-state species generated in the source interact with reagent molecules and polar or non-polar analyte present near the inlet of the mass spectrometer.
What are the Uses of DART®?
Analysis of hundreds of chemicals, including pharmaceuticals, their metabolites, peptides, oligosaccharides, synthetic organic molecules, organometallics, explosives and toxins has shown that the DART® is a versatile method for rapid detection of analytes. These chemicals have been detected on surfaces including concrete, asphalt, human skin, currency, paper stock, vegetables, fruit, and even clothing. For specific examples see the applications page.
How DART® Works
An electrical discharge creates a plasma as inert gas flows through the DART® chamber. The plasma contains ions, electrons, and excited neutral atoms and molecules. Electrostatic lenses in the DART® remove ions and electrons, leaving only long-lived electronically or vibronically excited atoms and molecules (metasables). A grid at the exit of the DART® source prevents ion-electron recombination and acts as an electron source for negative-ion formation. A heater coil increases the temperature of the gas as it travels towards the exit orifice of the source. An insulator cap ensures that no exposure to high voltage occurs outside the plasma chamber. The heated gas containing neutral but highly energetic atoms and molecules exits the source heading towards the inlet of the atmospheric pressure ionization mass spectrometer.
The ions produced in the vapor phases between the DART® insulator cap and mass spectrometer inlet are formed by interaction of the electronic excited-state species of helium or neon or vibronic excited-state species of nitrogen with the sample. The heated gas also assists in desorption of molecules on the surface of materials placed along the path between the cap and inlet.