There are several methods of ionization that can be used in mass spectrometry. Chemical ionization uses reagent ions to react with analyte molecules and form ions through proton or hydride transfer. Electron impact ionization uses an electron beam to knock electrons off analyte molecules, creating ions. Electrospray ionization sprays a sample solution to form charged droplets that evaporate and leave behind highly charged analyte molecules. Matrix-assisted laser desorption ionization disperses biological molecules in a solid matrix and uses a laser to carry the ionized molecules into the gas phase for analysis.