Ionization happens in two distinct steps: 1) the analyte needs to desorb from the surface and 2) it has to react with the “magic soup” to form an ion. We typically use the closed end of a melting point capillary, but anything that fits into the sampling gap can be analyzed. To analyze a sample, you simply place the analyte into the “magic soup” using a surface of your choice. A small diaphragm vacuum pump keeps the DART gas and neutral analytes moving through the ion source while charged analytes are pulled into the mass spectrometer orifice by electrostatic attraction. The choice of DART gas and its temperature are user controllable parameters. This generates neutral, excited, “metastable” gas atoms/molecules, which interact with the air in the sampling region to create a “magic soup” of excited gas and water vapor. Inside the DART ion source, an inert gas (nitrogen or helium) passes over a heater, through a plasma, and, finally, an electrode that traps charged species. DART does NOT work for very polar molecules, like sugars and peptides, but we can help you analyze those with ESI. You should probably use our GC-Exactive instrument for those samples. It doesn’t work well for very apolar molecules, like unsaturated hydrocarbons. DART can also be used in the analysis of synthetic polymers and plastics. It is very quick and requires little to no sample preparation. DART BasicsĭART is an open-to-atmosphere, surface-desorption ionization method that works for most of small to medium sized organic and organometallic analytes. Mass spec should NOT be used to measure purity, except in special cases.
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