A rapid spectrophotometric procedure for the simultaneous micro determination of carbamazepine and 5, 5-diphenyl-hydantoin in blood.

Carbamazepine and 5,5-diphenylhydantoin are simultaneously extracted from 100-200 mul blood with 1,2-dichloroethane. 5,5-Diphenylhydantoin is removed by a one-step wash into alkali. The dichloroethane is further washed with acid and then evaporated to dryness. 5,5-Diphenylhydantoin is determined in the alkali washing by a benzophenone procedure; carbamazepine is determined in the dried residue by the 9-methylacridine procedure earlier described. The combined method is rapid, reliable and has a detection threshold of less than 0.1 mg/100 ml for each drug.