Sulbactam: Alkaline Degradation and Determination by High-Performance Liquid Chromatography

Abstract

Although sulbactam has no ultraviolet (UV) absorption maximum above 200 nm, it was found to be easily degraded in alkaline methanol and in alkaline aqueous solution to yield products having UV absorption maxima at 267 nm and 278 nm, respectively. An ion-pair reversed-phase high-performance liquid chromatographic (HPLC) method utilizing this alkaline degradation as a postcolumn reaction has been developed for the determination of sulbactam in plasma and urine. A high and reproducible detector response due to the degradation product(s) was obtained when methanol was used as an organic modifier of the eluent. The HPLC and postcolumn reaction conditions were as follows: column, Develosil ODS-10 (25 cm x 4.6 mm i.d.); eluent, 5mM tetra-n-butylammonium bromide +1 mM Na2HPO44-lmM NaH2PO4 solution/ methanol = 3/1 (v/v) for urine samples and 2/1 (v/v) for plasma samples; flow rate, 1.2ml/min; postcolumn reagent, 0.5 N aqueous NaOH solution at a flow rate of 0.6ml/min; reaction coil, 2m x 0.25mm i.d.; detection, 276nm. The procedure was quantitative over a wide range of sulbactam concentrations in plasma and urine down to 0.2μg/ml and 1.0μg/ml, respectively. The intra- and inter-assay precisions for plasma at a sulbactam level of 0.53 μg/ml were of the order of 2.0% and 3.5%, respectively. © 1984, The Pharmaceutical Society of Japan. All rights reserved.