[Determination of the by-product 10-bromocarbamazepine in the drug carbamazepine with DC- and differential pulse polarography].

The quantitative determination of the impurity 10-bromocarbamazepine (caused by manufacturing method) in the drug carbamazepine is possible by using their cathodic two-electron debromination at a dropping mercury electrode in tetraethylammonium perchlorate/acetonitrile or 80% aqueous methanol as supporting electrolyte. Direct current polarographic (dcp) and differential pulse polarographic (dpp) methods are described which can be used in process control and quality control of the drug production. These analytic methods allow to determine 10-bromocarbamazepine in carbamazepine up to a limiting concentration of 3 X 10(-5) mol/l (100 ppm bromine; dcp) and of 3 X 10(-6) mol/l (10 ppm bromine; dpp). On the basis of electroanalytical results the mechanism of the polarographic reduction of 10-bromocarbamazepine is discussed.