Oxidative coupling for the spectrophotometric determination of certain cephalosporins and acetaminophen in drug formulations

A spectrophotometric method for the determination of some cephalosporins and acetaminophen is described. The method is based on the hydrolysis of the cephalosporin in sodium hydroxide solution to produce the sulphide ion and the conversion of the sulphide with the p-phenylenediamine to form a violet colour. Acetaminophen is hydrolysed in sulphuric solution and the resulting p-aminophenol is oxidized with sulphide ion in the presence of iron(III) to form a red product. The method has been successfully applied to the assay of some cephalosporins and acetaminophen in drug formulations.