Electrochemical Oxidation of 4-Chlorocatechol in the Presence of Some Sulphydryl Compounds: Applications to Voltammetric Detection of D-Penicillamine, Glutathione and L-Cysteine

Electrooxidation of 4-chlorocatechol at a glassy carbon electrode (gce) wasinvestigated in the presence of some biologically important thiols (rsh), e.g. dpenicillamine(d-pa), glutathione (gsh) and l-cysteine (l-cys) in aqueous media usingcyclic voltammetry (cv), differential pulse voltammetry (dpv) and double steppotential chronoamperometry methods. the 4-chlorocatechol exhibits strongelectrochemical response toward thiols oxidation in wide ph rang (2.00–9.00). theresults show that thiol-containing compounds participate in michael addition reactionswith 4-chlorocatechol to form the corresponding thioquinone derivatives. the reoxidationof the adduct leads to an increase in the anodic current. therefore, in theoptimum condition (ph=6.00) in cv, the oxidation of d-pa, gsh and l-cys in thepresence of 4-chlorocatechol occur at a potential about 420, 750 and 420 mv,respectively less positive than that in the absence of it. the kinetic parameters such aselectron transfer coefficient, ? and electrochemical reaction rate constant, kh wasdetermined using electrochemical approaches.