after derivatization with o-phenylenediamine in acidic medium and extraction , the 2-ketoacids , and the 2-ketovaleric acid used as internal standard , are silylated and resolved on a capillary column and their concentrations automatically determined by monitoring the m/z values corresponding to their respective protonated molecular ions , using ammonia as reactant gas .
C0002607
ammonia
C0017110
gas