Visible spectrophotometric determination of cephalosporins and penicillins by indophenol derivatization with and without alkaline degradation to ammonia.
Cephalosporins and penicillins give reproducible yields of ammonia on degradation in 0.5 M sodium hydroxide solution at 100 degrees C: the ammonia formed was determined in the degraded solutions using the indophenol reaction. In another approach the ammonia driven off on refluxing alkaline solutions of the cephalosporin or penicillin was collected in dilute hydrochloric acid solution and determined using the indophenol reaction. For eight of the fourteen cephalosporins and penicillins studied identical yields were recorded using the two procedures: these varied from 29% for penicillin G to 137% for cephalonium based on the production of one ammonia molecule per beta-lactam molecule. For six other cephalosporins the distillation method gave substantially higher yields of ammonia than did the direct determination. Eight cephalosporins and penicillins were found to give substantial indophenol-type reactions without prior hydrolysis of the beta-lactam, but the sensitivities were usually lower than for the hydrolysis method. Manual spectrophotometric procedures for the determination of cephalosporins and penicillins based on these reactions have been developed.
Fogg
A G
AG
Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, LE11 3TU, UK.
Abdalla
M A
MA