Identification of the Related Substances in Ampicillin Capsule by Rapid Resolution Liquid Chromatography Coupled with Electrospray Ionization Tandem Mass Spectrometry

Table 1

The structures of the known related substances of ampicillin.

Number	Name of related substances	Chemical structure
1	6-Aminopenicillanic acid (6-APA)
2	L-Ampicillin
3	Diketopiperazines of ampicillin
4	Ampicilloic acid
5	Ampilloic acid
6	Ampicillinyl-D-phenylglycine
7	(3R,6R)3,6-Diphenylpiperazine-2,5-dione
8	3-Phenylpyrazin-2-ol
9	D-Phenylglycylampicillin
10	N-Pivaloyl-6-APA
11	N-Pivaloylphenylglycine
12	D-Phenylglycine
13	Open-cycle dimer
14	Closed-cycle dimer
15	Open-cycle trimer
16	Closed-cycle trimer
17	Open-cycle tetramer ()
18	Closed-cycle tetramer ()