Spectrophotometric assay of clavulanic acid by reaction with imidazole

Abstract

An assay method for salts of clavulanic acid is based on the absorbance at 312 nm of the product of reaction with imidazole. The reaction product has been isolated and identified as 1-(4-aza-8-hydroxy-6-oxo)oct-2-en-1-oylimidazole. The method is applicable to clavulanate concentrations of down to about 2 µg ml^–1 and is specific for intact clavulanate in the presence of degradation products. Derivatives of clavulanic acid and other compounds containing the clavam nucleus also give strongly absorbing products under the assay conditions, but penicillins give little or no absorbance.