An improved UV-spectrophotometric method for routine barbiturate monitoring

A simple, rapid, quantitative, low-cost UV-differential spectrophotometric method for the routine monitoring of phenobarbital in serum and cerebrospinal fluid is described. This method can also be used for monitoring methylphenobarbital (Phemiton) and primidone (Mysoline), since the major active metabolite of both drugs is phenobarbital. The basis for our procedure is Goldbaum's method (Anal. Chem., 24, 1604 (1952)). This method was improved with several modifications including a single extraction technique with dichloroethane, which has produced a very simple but still accurate method. The whole analysis takes less than 20 minutes. This procedure is accurate in the range from 1-100 mg/1 of phenobarbital in serum or cerebrospinal fluid.