Fluorometric determination of cephalexin, cephradine, and cephatrizine in biological fluids.

Intensely fluorescent products were formed from cephalexin and cephradine in acidic solution containing hydrogen peroxide by hydrolysis at high temperature. A fluorescent product was formed from cephatrizine in solutions containing mercuric chloride by warming at 60° for 50 min after cleavage of the β-lactam ring with 1N NaOH. Each of the fluorescent products was readily extracted with ethyl acetate or an acetone-chloroform mixture from neutral solutions, and could be partitioned into alkaline solution. The urinary excretion of these antibiotics in human volunteers after oral administration was investigated using these new methods.