Simultaneous determination of N-unsubstituted and N-substituted nitroazoles and criteria for their identification-III Chromatographic separation and polarographic determination of halo-nitroimidazoles

Methods for identifying and determining halo-nitroimidazoles appearing together during synthetic processes, regardless of the preparation methods, are proposed. Polarographic determination can be used in all synthetic processes when halo-nitroimidazoles have been obtained by nitration of the halo-imidazoles. When the halo-nitroimidazoles have been obtained from 5(4)-halo-4(5)-nitroimidazoles by substitution of the imino hydrogen atom, and when only one N-substituted derivative has been obtained in a reaction mixture, simultaneous polarographic determination of both compounds is possible, but only when an alkaline medium is used as supporting electrolyte. In some cases, simultaneous polarographic determination of all three compounds present in a reaction mixture during N-substitution processes [one 5(4)-halo-4(5)-nitroimidazole and two N-substituted isomers] is also possible with alkaline supporting electrolyte. Explanations are given of the phenomena on which the simultaneous polarographic determination is based. When simultaneous polarographic determination cannot be used to determine the amount of each polarographically-active compound present in a reaction mixture, the compounds can be separated chromatographically and then determined individually by polarography.