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

Table 2

Results of identification of the known related substances in ampicillin capsule.

Peak number	RT (min)	MS ()	MS^2 ()	Identification
1	1.8	368.1 [M + H]^+	324.1; 307.1; 279.2	(5S, 6R) ampicilloic acid
2	2.2	368.1 [M + H]^+	324.1; 307.2; 279.2; 175.1	(5R, 6R) ampicilloic acid
3	2.5	350.1 [M + H]^+	333.0; 192.0; 174.0; 160.0; 106.1	L-Ampicillin
4	2.8	324.1 [M + H]^+	307.0; 279.1; 201.0; 175.0; 147.1; 128.1; 106.1	(5S) or (5R) ampilloic acids
5	4.2	350.1 [M + H]^+	333.1; 192.0; 174.0; 159.9; 106.2	Ampicillin
6	8.1	364.1 [M + K^+H]^+	191.9; 174.0; 128.0; 106.2	(5S) or (5R) ampilloic acids
7	9.0	382.1 [M + MeOH]^+	331.1; 223.0; 206.0; 160.0; 106.2	Diketopiperazines of ampicillin
10	12.3	483.1 [M + H]^+	439.1; 350.0; 267.0; 239.1	D-Phenylglycylampicillin
15	17.0	699.1 [M + H]^+	540.1; 381.1; 248.0	Closed-cycle dimer
16	19.3	524.8 [1/2M + H]^+	889.3; 730.3; 571.2; 160.0	Closed-cycle trimer