Identification of metabolites of ampicillin using liquid chromatography/thermospray mass spectrometry and fast atom bombardment tandem mass spectrometry

Abstract

Mass spectrometry is combined with liquid chromatography (LC/MS) and mass spectrometry (MS/MS) to identify ampicillin and two known metabolites--ampicillin penicilloic acid and ampicillin piperazine-2,5-dione--in human urine samples. Identifications were based on the fact that the metabolites or degradation products contain a substructure of ampicillin. In addition, two previously unidentified components in human urine samples were detected, corresponding to newly discovered metabolites or degradation products of ampicillin. Different chromatographic retention times in the LC mass spectra indicated two different compounds. However, the tandem mass spectra of these two components were similar, suggesting that they are stereoisomers. The use of LC/MS and MS/MS confirmed that the unknown components are the (3S,5R) and (3S,5S) epimers of ampicillin penilloic acid. Further study showed that only one of the components was eliminated from the body; the other arises from interconversion to the epimer in a urine sample. It is speculated that the component produced in vivo is the (3S,5R) epimer of ampicillin penilloic acid.

Utility of surface enhanced Raman spectroscopy (SERS) for elucidation and simultaneous determination of some penicillins and penicilloic acid using hydroxylamine silver nanoparticles

“…The component of the chromatographic peak at 0.9 min is identified as ampicillin as confirmed by mass spectrum (Fig. S3B) which contains an abundant ion at m/z 350, corresponds to protonated ampicillin [25]. Fig.…”

Research on degradation of penicillins in milk by β-lactamase using ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry

“…Time-of-flight-mass spectrometry was combined with LC to identify the penicillins and their metabolites. Identifications were based on the fact that the metabolites or degradation products contain a substructure of penicillin (Suwanrumpha and Freast, 1989). To select the most sensitive ion pairs, a full-scan mass scan was first applied to identify the precursor ions by direct flow injection.…”

“…Loss of 1 molecule of carbon dioxide at C-6 removes 1 of the molecule's chiral centers. Nevertheless, the center at C-5 remains intact and, therefore, 2 isomers can be found: 5R-penilloic acid and 5s-penilloic acid (Suwanrumpha and Freast, 1989). In strong acid medium (pH 2 or less), penicillins are isomerized to penilloic acid by a mechanism involving the transient oxazolone structure (Blaha et al, 1976).…”

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

“…All of them produced protonated quasimolecular ion at m / z 368.1 [M + H] + , major ions at m / z 324.1, 307.1, 279.2, and 175.1 in ESI + mode. Based on diagnostic ions ( m / z 324.1, 307.1, and 175.1) and comparison with the published literature of known related substances of ampicillin [ 10 ], Peak 1 and Peak 2 were identified as isomers of ampicilloic acid. (5S, 6R) or (5R, 6R) ampicilloic acids were the two groups of ampicilloic acid isomers which were reported to be the metabolites and degradation products of ampicillin [ 1 ].…”

“…Peak 4 gave a protonated molecular ion [M + H] + with an m / z value of 324.1, major fragment ions at m / z 307.0, 279.1, 201.0, 175.0, 147.1, 128.1, and 106.1 in ESI + mode. Peak 4 was tentatively identified as (5R) or (5S) ampilloic acid based on its characteristic ions ( m / z 324.1, 307.0, 279.1, 128.1, and 106.1) and comparison with the published literature of known related substances of ampicillin [ 10 ]. Peak 6 produced major fragment ions at m / z 364.1 [M + K + H] + , 191.9, 174.0, 128.0, and 106.2.…”