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.