質子傳遞

傳遞的質子是從水合氫離子（H3O +）而來，對於質子親和力比水大的物質和基團如乙醇、醚、羰基、羧基等都很容易進行質子傳遞；因為大多數被氧化的有機物，比如那些存在於氣溶膠中的有機物都含有很多這樣的基團，所以質子親和力都比水大，在質子傳遞中用水合氫離子進行化學電離有望是一種高效並相對温和的使有機物電離的方式。

對應的英文解釋是：

Proton-transfer-reaction (PTR) is one form of chemical ionization that has proven to be an effective technique for the measurement of many ambient VOCs . Proton transfer from hydronium ions (H3O+) is efficient for species with a proton affinity (PA) higher than that of H2O (691 kJ/mol), including molecules with alcohol, ether, carbonyl, carboxyl, nitrile, amine, or aromatic groups. Since most oxidized organic species, such as those expected to comprise much of the aerosol organic mass fraction, have a higher proton affinity thanwater, proton transfer chemical ionization using H3O+ is expected to be an effective, and relatively soft, form of ionization for these compounds.