Fluorometric determination of ampicillin and aminobenzylpenicilloic acid in presence of pivampicillin in body fluids

Isolation and identification of a fluorophore from ampicillin degradation

A fluorescent impurity in ampicillin has been isolated and identified as 2-hydroxy-3-phenylpyrazine. The product is formed under acidic conditions similar to those employed in some fluorometric assay procedures. The mechanism of the reaction is proposed to involve cyclization by condensation of the penilloaldehyde of ampicillin. The structure was confirmed by independent synthesis.

Isolation and identification of the fluorescent degradation product of some beta-lactam antibiotics

A fluorescent degradation product of cephalexin, recently employed in the determination of this antibiotic in aqueous solution and human plasma, has been isolated and identified as 2-hydroxy-3-phenyl-6-methylpyrazine. Spectroscopically and chromatographically the product is indistinguishable from that obtained by the same method from a series of other cephalosporins and penicillins bearing an alpha-amino group on the side-chain, and from the pyrazine structure produced by synthesis. Two reported methods for the fluorimetric determination of ampicillin have also been found to yield the same degradation product and not the suggested diketopiperazine structure.