Search results
Results from the WOW.Com Content Network
Electrospray ionization (ESI) is a technique used in mass spectrometry to produce ions using an electrospray in which a high voltage is applied to a liquid to create an aerosol. It is especially useful in producing ions from macromolecules because it overcomes the propensity of these molecules to fragment when ionized.
The above table simplifies the dopant process. In fact, there may be extensive ion-molecule chemistry between dopant and solvent before the analyte becomes ionized. APPI can also produce negative ions by creating a high abundance of thermal electrons from dopant or solvent ionization or by photons striking metal surfaces in the ionization source.
The number of publications about electrospray started rising significantly around 1990 (as shown in the figure on the right) when John Fenn (2002 Nobel Prize in Chemistry) and others discovered electrospray ionization for mass spectrometry.
Ambient ionization techniques are attractive for many samples for their high tolerance to complex mixtures and for fast testing. EESI has been employed for the rapid characterization of living objects, [ 10 ] native proteins , [ 11 ] and metabolic biomarkers .
The ions generated from atmospheric or dopant molecules undergo ion-molecule reactions with the sample molecules to produce analyte ions. Analytes with low ionization energy may be ionized directly. The DART ionization process can produce positive or negative ions depending on the potential applied to the exit electrode.
One example is electrospray laser desorption ionization (ELDI), which uses an ultraviolet laser to form ions by irradiating the sample directly, then interacting with the electrospray plume without using any matrices. [40] The infrared version of ELDI has been referred to as laser ablation electrospray ionization (LAESI). IR-MALDESI differs ...
Probe electrospray ionization is an ambient ionization mass spectrometry technique developed by Kenzo Hiraoka et al. at the University of Yamanashi, Japan. [4] The technique was developed to address some of the issues associated with traditional electrospray ionization (ESI), including clogging of the capillary and contamination, whilst providing a means of rapid and direct sample analysis.
Secondary electrospray ionization mechanism diagram. In the early days of SESI, two ionization mechanisms were under debate.: the droplet-vapor interaction model postulates that vapors are adsorbed in the electrospray ionization (ESI) droplets, and then reemitted as the droplet shrinks, just as regular liquid phase analytes are produced in electrospray ionization; on the other hand, the ion ...