electrosprayionisoinnissa

Electrospray ionization (ESI) is a soft ionization technique used in mass spectrometry. It is particularly well-suited for ionizing molecules in solution, making it a common interface between liquid chromatography (LC) and mass spectrometry (LC-MS). In ESI, a high voltage is applied to a liquid flowing through a capillary, creating a fine spray of charged droplets. As the solvent evaporates from these droplets, the charge density on the remaining ions increases, leading to Coulombic fission. This process breaks down the droplets into smaller ones until individual ions are ejected into the gas phase. The gentle nature of ESI typically produces intact molecular ions, often in the form of protonated or deprotonated species, making it ideal for analyzing fragile biomolecules like peptides, proteins, and nucleic acids, as well as small organic molecules. The technique can operate in both positive and negative ion modes, depending on the polarity of the applied voltage and the analyte's propensity to accept or lose a proton. ESI is widely used in fields such as pharmaceutical analysis, environmental monitoring, and proteomics due to its high sensitivity and ability to handle complex mixtures.