Determination of Dialkyltriazenoimidazoles by Nonaqueous Titration

An analytical method for dialkyltriazenoimidazoles has been developed. It serves as a reliable purity check on these anticancer drugs whose effectiveness is a function of their purity. The method consists of titration in nonaqueous media with perchloric acid. The titrant, perchloric acid, is dissolved in a nitroethane-chlorobenzene mixture. Samples are dissolved in glacial acetic acid or in acetonitrile. Poor solubility of some of the compounds is overcome by the selection of an appropriate solvent system, chosen to give also optimum titration end-points. The electrode system consists of conventional glass and calomel electrodes. The method is directly applicable to the unstable 5(or 4)-[3,3-bis(2-choloroethyl)-1-triazeno]imidazole-4(or 5)-carboxamide, without interference by its transformation product, 1-(2-chloroethyl)-3-[5(or 4)-carbamoyl-imidazol-4(or 5)-yl]-v-triazolinium chloride, usually present in small amounts.