Neutral molecule ionization, ion pair formation, ion neutralization and ion yield estimation: For analytes that lack acidic groups such as carboxylic, phosphoric and sulfuric acid groups, contribution of ions from autoprotolysis will be limited. In the cases that the analytes have electron donor groups such as ether, alcohol, aldehyde, ketone, ester, amine, amide, nitro, cyano, guanidine, imidazole and pyridine groups, protonation by acidic matrix molecules and coordination with metal cations from residue salts can be the major pathway for ionization (equations 12-14).