Redox reactions in non-aqueous media: determination of organic isothiocyanates alone, in formulations and in important mixtures.
A simple potentiometric method for the determination of organoisothiocyanates is described. The isothiocyanate is treated in acetonitrile medium with an excess of primary amine to convert it into a substituted thiourea and the surplus amine is converted into a dithiocarbamate by addition of carbon disulphide. The solution is then titrated with a copper(II) solution in acetonitrile. The three-step titration curve enables the results to be calculated on the bash of the dithiocarbamate and/or thiourea formed. The method has been successfully applied to the analysis of a commercial insecticide formulation based on isothiocyanate and important mixtures containing isothiocyanates.
Voltammetric and electrochemical quartz crystal microbalance studies of sulforaphane and its Zn(II) complexes.
Cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) methods were used to study the behavior of sulforaphane (SFR). To established electrochemical properties of SFR methyl-, ethyl-, 2-chloroethyl-, propyl-, butyl- and tert-butyl-isothiocyanates were examined at gold electrode. Optimal measurement parameters were established and stock solutions developed. The electrode activity of the studied compounds (cathodic peak E(p)=-0.6 V) was found to be primarily due to the oxidation of the isothiocyanate group. By the EQCM method it was found that during the reduction of SFR the mass of the electrode systematically increased in successive scans by ca. 120 ng per scan and in the mixture of SFR and Zn(2+) ions ca. 350 ng. Formation of SFR complexes with Zn(2+) ions was confirmed by EQCM and UV methods. Cyclic voltammetric method has been elaborated for SFR determination and compared with UV method.
Jodimetric estimation of water-soluble dithiocarbamates
SummaryIodimetric estimation of dialkyl dithiocarbamate in alcoholic solution is not accurate. The method has not met with success for the water-soluble dithiocarbamates before. A simple and accurate iodimetric method has been developed for the estimation of water-soluble dithiocarbamates. The success of the method is due to the removal of the oxidation product which interferes during the titration with iodine.