31: Which liquid chromatography/mass spectrometry interface, atmospheric pressure chemical ionization or electrospray, requires analyte ions to be in solution prior to the interface? How does the other interface create gaseous ions from neutral species in solution?

Mass spectrometry is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio.

Atomic Pressure chemical ionization and electrospray ionization are both techniques used in ionizing eluates from chromatography column so that they can be analyzed by the mass spectrometer.

To produce gaseous ion from analyte molecule that usually have some volatility,atomic pressure chemical ionization use N₂ to aerosolize the eluent. The eluent is then exposed to the electric corona formed by applying high voltage to metal needle. The electric corona formed on the needle’s surface injects electrons into the aerosolized eluent, creating the ions to be analyzed by the mass spectrometer.

Usually the eluent being ionized by electrosprays were already in solution before they get ionized.